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Biology and ecology of Aphis gossypii Glover (Homoptera: Aphidiae)

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Abstract

Aphis gossypii Glover is a destructive pest of over two dozen crops world wide. Damage to a few of these crops is due to direct feeding, but for most of these crops its impact is through its role as a virus vector.As expected, this has resulted in many articles dealing with methods of controlling this insect. The aphid has the ability to become resistant to many pesticides and there is growing concern over environmental impacts of pesticide use. As a result, manipulation of the agroecosystem will playan ever increasing role in the management of this insect. Most aspects of the biology of this aphid are covered in this review. The recurrent theme centers around the importance of host plant influences on the biology of the aphid. In addition to examining the literature on the biology of the aphid, a large section is devoted to organisms which influence mortality in the aphid, and to aphid borne viruses transmitted by this aphid. This review covers the literature from 1912 to 1995, but articles on aphid management (e.g. pesticide efficacy, planting date) were omitted except where they deal with the aphid's biology or ecology. Research on the biology of this aphid has been heavily skewed into several disparate categories. First, research has focused on the influence of host plant and temperature on the reproductive rate of this aphid. Second, research has focused on the cause for alate production such as nutritional stress, other nutritional factors, crowding, and temperature. Third, research has focused on the viral borne pathogens transmitted by this aphid. Three specific cases are highlighted; citrus tristeza, cucumber mosaic virus, and the potyviruses. Last, research has focused on the role of organisms which feed on this aphid. Due to the complexity of research possible in this area, very little research has explored the effect of these 'beneficial organisms' on life history traits of this aphid.
BIOLOGY AND ECOLOGY OF APHIS GOSSYPII GLOVER (HOMOPTERA: APHIDIDAE)
T. A. Ebert
1
and B. Cartwright
2
Department of Entomology
Oklahoma State University
Stillwater, OK 74078
ABSTRACT
Aphis gossypii Glover is a destructive pest of over two dozen crops
world wide. Damage to a few of these crops is due to direct feeding, but for
most of these crops its impact is through its role as a virus vector. As
expected, this has resulted in many articles dealing with methods of
controlling this insect. The aphid has the ability to become resistant to
many pesticides and there is growing concern over environmental impacts of
pesticide use. As a result, manipulation of the agroecosystem will play an
ever increasing role in the management of this insect.
Most aspects of the biology of this aphid are covered in this review.
The recurrent theme centers around the importance of host plant influences
on the biology of the aphid. In addition to examining the literature on the
biology of the aphid, a large section is devoted to organisms which
influence mortality in the aphid, and to aphid borne viruses transmitted by
this aphid. This review covers the literature from 1912 to 1995, but
articles on aphid management (e.g. pesticide efficacy, planting date) were
omitted except where they deal with the aphid's biology or ecology.
Research on the biology of this aphid has been heavily skewed into
several disparate categories. First, research has focused on the influence
of host plant and temperature on the reproductive rate of this aphid.
Second, research has focused on the cause for alate production such as
nutritional stress, other nutritional factors, crowding, and temperature.
Third, research has focused on the viral borne pathogens transmitted by this
aphid. Three specific cases are highlighted: citrus tristeza, cucumber
mosaic virus, and the potyviruses. Last, research has focused on the role of
organisms which feed on this aphid. Due to the complexity of research
possible in this area, very little research has explored the effect of these
"beneficial organisms" on life history traits of this aphid.
INTRODUCTION
Aphis gossypii Glover is an important agricultural pest because it has a
broad host range, and transmits many agriculturally important plant viruses.
Damage is direct through feeding which can kill the host, but also
productivity is reduced long before plant death (Andrews and Kitten 1989,
Cartwright 1992). Damage is indirect through contamination with aphid
honeydew and by vectoring viral pathogens. Honeydew causes economic loss
through physical contamination and through providing a nutrient source for
fungi that contaminate produce and reduce photosynthesis rates by blocking
sunlight.
In the past, this aphid has been controlled with a wide array of
insecticides. The growing concern over the use of pesticides is a major
theme in much of agriculture due to environmental contamination and the
economic impact of pesticide resistance. The response in the USA is to
promote reduced dependence on pesticides, increased reliance on beneficial
organisms, and increased government regulation of chemical use. To continue
to control the pest under these conditions requires a detailed knowledge of
pest biology and the pest's interactions with other organisms and the
environment.
1
Laboratory for Pest Control Application Technology, Ohio Agricultural
Research and Development Center, The Ohio State University, 1680 Madison
Ave, Wooster, OH 44691 (email: ebert.39@osu.edu)
2
MERC INC., 180 Ashwood circle, Plano TX 75075
This review summarizes the literature on A. gossypii published from 1912
to 1995 with a few articles from 1996. The goal is to provide information to
help future research, and provide a key into the literature. While this
review is fairly comprehensive, articles on aphid management (e.g. pesticide
efficacy, planting date, and seasonal differences) were omitted except where
they provide insight or corroborative detail on the biology or ecology of
the aphid. Especially in the case of seasonality, this should not be taken
as an indication that the effect is unimportant (see Slosser 1993, Slosser
et al. 1992). However, the critical elements of season which are the driving
force in the relationship (light, temperature, rainfall, humidity, plant
growth stage, etc.) are more carefully studied elsewhere.
Because host plants are an important aspect in the biology of this
aphid, old taxonomic names were converted into modern equivalents. Where
possible, the work by Huxley et al. (1992) was used along with the
conventions therein. Tanaka (1976) was used if the plant was not found in
Huxley et al. A dagger "†" after the scientific name indicates use of an
updated scientific name. The work by Jones and Luchsinger (1986) was used as
a source for the Cronquist system of plant evolution.
MORPHOLOGY
External morphological characters can be used to distinguish different
life stages of this aphid. Cornicle length can separate instars of A.
gossypii reared under fluctuating temperatures. There was considerable
overlap between instars, but there was no overlap between nymphs and adults
(Singh and Srivastava 1989). Other characters combined can provide greater
separation between instars especially under constant temperatures (Inaizumi
and Takahashi 1989a). First-instar nymphs are distinguished by having four
antennal segments, while second-instar nymphs have five segments.
Differences between second- and third-instar nymphs are fairly small but at
constant temperatures they can be separated using a combination of
characters (body length, cornicle length, and setal number on cauda and anal
plate). Third-instar nymphs have no setae on the margin of the genital
plate, while fourth-instar nymphs have such setae. Second-instar nymphs with
developing wings appear to have shoulders, third-instar nymphs have small
wing pads, and the developing wings are prominent on fourth-instar nymphs.
Exact measurements are not provided as they will be different for different
host plants, and morphological differences due to host plant are much larger
than differences due to genetics (Wool and Hales 1996).
The following stages have been illustrated for this aphid from Japan:
fundatrix, fundatrigeniae, alienicola, gynoparae, oviparous female, alate
and apterous male, hibernating viviparae, virginandroparae, androparae,
heteroparae, and androgynoparae. There are also individuals with partly
developed wings from nearly apterous to nearly functionally winged (Inaizumi
1968, Inaizumi 1980, Inaizumi 1983) (for definitions of the life stages see
[Miyazaki 1987, Moran 1992] but also see [Blackman 1994]). The following
stages have been illustrated for this aphid from Iran: alate and apterous
viviparae (Ghovanlou 1974).
The internal morphology of A. gossypii has received little attention.
However, one paper describes the morphology of the brain of A. gossypii
reared on Brassica sp. (Satija and Dhindsa 1968).
LIFE HISTORY
Host Range. The world wide distribution of A. gossypii is partly due to
its broad host range. Table 1 organizes the recorded hosts according to the
Cronquist system of plant classification (Jones and Luchsinger 1986). The
families listed are ones where at least one plant species has been recorded
as a host, but with no consideration of host suitability. The species listed
are plants useful to man where the aphid is sufficiently abundant to require
some type of human intervention. This organization emphasizes the diversity
of the host range and the impact this aphid has on human activities.
In addition to records of hosts from which this aphid has been
recovered, the host switching ability of this aphid is also documented. One
study reported A. gossypii surviving at least 15 days following transfer
from plants in the Scrophulariaceae, Brassicaceae, Asteraceae, Lamiaceae,
Rosaceae, and Malvaceae to plants in the Asteraceae, Solanaceae,
Cucurbitaceae, Liliaceae, Portulacaceae, Commelinaceae, and Araceae
(Inaizumi 1980). Another study reported colonies on plants in the
Cucurbitaceae surviving at least 3 months following transfer to plants in
the Begoniaceae, and Onagraceae (Batchelder 1927). In addition, colonies
from plants in the Cucurbitaceae survived over 2 years following transfer to
hosts in the Poaceae (Ebert 1994). However, it is also clear that there are
many biotypes of this aphid (Guldemond et al. 1994), where biotype is
defined as the ability or inability to feed on specific hosts within the
host range of the species. Several authors have designated biotypes for this
aphid, but they are only of local interest because a lack of standardization
precludes comparisons of biotypes.
Host Utilization. Reproduction in A. gossypii is mostly asexual with
either alate or apterous females. In warmer environments, this aphid
exhibits an anholocyclic life cycle, while in cooler areas the aphid
exhibits either a heteroecious or autoecious holocyclic life cycle (Slosser
et al. 1989, Zhang and Zhong 1990). The heteroecious cycle involves a
migration from a primary host to a secondary host in the spring and a return
to a primary host in the fall for laying eggs. The primary host for the
aphid is the original host for the aphid, but there are problems with using
this definition if the aphid has multiple primary hosts. In Japan, this
aphid lays eggs on Citrus (Rutaceae), Hibiscus syriacus L. (Malvaceae),
Rhamnus dahuricus† Pall. (Rhamnaceae), Celastrus orbiculatus Thunb.
(Celastraceae), and Rubia cordifolia L. (Rubiaceae) (Inaizumi 1980, Komazaki
et al. 1979). In the USA, this aphid lays eggs on H. syriacus and Catalpa
bignonioides Walter (Bignoniaceae) (Kring 1959). In the Peoples Republic of
China, this aphid lays eggs on Zanthoxylum simulans Hance (Rutaceae),
Rhamnus sp. (Rhamnaceae), and Punica granatum L. (Lythraceae) (Zhang and
Zhong 1990).
It has been suggested that Z. simulans was the original host of this
aphid (Zhang and Zhong 1990). The rationale was that this host was the more
primitive host where sexuals overwinter and that the aphid life cycle is
better synchronized with Z. simulans relative to P. granatum, and Rhamnus
sp. In Japan, A. gossypii on H. syriacus will move onto secondary hosts. Of
the primary hosts, the aphids did best in the transfer from H. syriacus
relative to the other primary hosts examined (Z. simulans was not examined)
(Inaizumi 1980). The argument against H. syriacus as the primary host was
that A. gossypii is almost completely autoecious on this host (in China),
and this host is more advanced than either P. granatum, or Rhamnus sp (Zhang
and Zhong 1990).
This conflict highlights fundamental problems in using plant biology or
plant phylogeny for determining the original host for a polyphagous species.
First, until the geographical point of origin for the aphid is known, the
degree of synchronization will not help identify the original host of the
aphid. This is because authors from different countries will find different
plants best synchronized with the aphid based on local host availability and
climate. Second, considering its polyphagous nature, the aphid may
secondarily adopt a new primary host that is more primitive than the "true"
original host. In conclusion, the original host plant for this aphid will
remain unknown - at least until more is known about the aphid's biology on a
global scale.
Population Growth. Reproductive rates in A. gossypii are reported in
two ways; net reproductive rate (R
o
), which is an interaction between birth
rate and survival rate (Wilson and Bossert 1971), and birth rate as measured
in nymphs produced per day per aphid. The additional information required to
estimate R
o
is more difficult to obtain than just the birth rate. As a
result, authors estimating R
o
and other life table parameters use a single
host plant at several different temperatures. Authors using birth rate
examine differences in aphids feeding on different host plants.
R
o
has been estimated for this aphid on many hosts: squash (Cucurbita
pepo L.) (Aldyhim and Khalil 1993), citrus (Citrus unshiu Marc.) (Komazaki
1982), pumpkin (may be squash, no scientific name provided) (Liu and Perng
1987), Veronica persica Poir (Nozato 1987a), taro (Colocasia esculenta
(L.) Schott. (Setokuchi 1981), and cucumber (Cucumis sativus L.) (Kocourek
et al. 1994, Owusu et al. 1994b, van Steenis and El-Khawass 1995, Wyatt and
Brown 1977). The interaction between host plant and temperature is apparent
when examining R
o
estimated by several different authors on several
different hosts: on squash the maximum R
o
(79.7) was at 25°C with a 15%
decrease at 30°C (Aldyhim and Khalil 1993); in citrus the maximum R
o
(58.68)
was at 19.8°C with a 6% decrease at 29.7°C (Komazaki 1982); in pumpkin the
maximum R
o
(109.14) was at 21°C with a 44% decline at 30°C (Liu and Perng
1987). Comparing the results from research on cucumber gives some idea of
the variability induced by differences in biotype augmented by differences
in experimental procedure. The differences include 1) location (United
Kingdom, Japan, Czech Republic, Netherlands); 2) confinement (leaf discs,
whole leaf cage?, leaf clip cages); 3) colony age (unknown, field collected,
64 generations); and 4) range of abiotic variables examined. At a day length
of 16.5 hours, 4000 versus 5000 lux, and temperature of 17.5°C, R
o
was
reported as 109.0 versus 41.9. At the same day length but 24.5°C, R
o
was
reported as 80.5 (Wyatt and Brown 1977) versus 51.6 (Kocourek et al. 1994).
Owusu et al. (1994b) did not report light intensity, but at about 25°C and
16 hours daylight, R
o
ranged from 32.9 to 49.8 for collections tested at
various times during the year. Also with an unknown light intensity, with a
14-hour day at 25°C, R
o
was reported as 53.0 (van Steenis and El-Khawass
1995). Equivalent estimates of R
o
under a range of light intensities at 16.5
hours daylight varied from 5.8 to 103.2 (Wyatt and Brown 1977).
Birth rate as a method for comparing aphid populations further
emphasizes host plant effects on A. gossypii biology. Significant
differences were found in birth rates of this aphid reared on cotton
(Gossypium hirsutum L.), watermelon (Citrullus lanatus (Thunb.) Matsum. &
Nakai), and groundnut (Arachis hypogaea L.) (Ekukole 1990). Significant
differences were also found in the reproductive potential of this aphid on
cotton, watermelon, sesame (Sesamum indicum L.), and eggplant (Moursi et al.
1985). Another study reported that development time was shortest on cotton,
longest on melon, with development rate on watermelon (Citrullus lanatus †)
lying somewhere between (Ghovanlou 1976). In contrast, one paper reported no
significant differences in birth rate for this aphid reared on okra
(Abelmoschus esculentus (L.) Moench.), eggplant (Solanum melongena L.), and
chili (Capsicum annuum var. annuum L.) (Kandoria and Jamwal 1988).
It is difficult to draw conclusions from these studies. Problems include
differences in aphid biotype (it is unknown, and may be different on
different host plants within a study), and the effects of different methods
of handling the insects (mainly cage effects). However, there are two papers
which examine the reproductive rate for this aphid on cotton: one from
Arizona in 1993 (Akey and Butler 1993), the other from Arkansas in 1946
(Isely 1946). The development time was shortest at 27.5°C and 28°C
respectively. At these temperatures, the aphids took 5.0 and 5.18 days to
reach maturity. The optimal temperature for fecundity as measured in
nymphs/adult/day was different: 25°C versus 20°C, which resulted in 2.85
versus 2.69 nymphs/adult/day respectively.
Stage Structure. One paper reported on the stage structure of field
collected aphids. By classifying nymphs as small, medium, and large, the
stage structure of this aphid on cotton in the USA was about 53% small
nymphs, 25% medium nymphs, 15% large nymphs, 5% apterous adults, and 2%
winged adults (Satoh et al. 1995).
Alate Production. There are two forces proposed as triggers for alate
production in A. gossypii: nutritional factors, and crowding. However,
research to date has not conclusively identified the relative importance of
nutrition versus crowding in alate formation in this aphid. The problem with
the nutritional studies is that they show increased alate production along
with increased total number of aphids. Studies on crowding eliminate
nutritional stress effects, but they do not eliminate other nutritional
factors. The problem is further complicated by insufficient knowledge of the
aphid's biology. There is no clear definition of "stress" for this aphid or
how to measure it. Frequently it is measured as a change in aphid fecundity,
but this is an average measure of stress rather than an instantaneous
measure. A similar problem occurs with defining crowding. There is no clear
understanding of what constitutes "crowded" from the aphid's perspective.
Papers which demonstrate crowding as the force behind alate development also
suffer from a lack of demonstrated (rather than theoretical) mechanism.
Aphid-aphid contact has been proposed, but it is equally likely that the
aphid has a chemical means of identifying the number of aphids on a leaf or
plant. Furthermore, it is not known if the trigger for alate production is
continuous, discrete, or a combination of the two. From nutritional studies
it would appear that those authors have assumed that they are looking at a
continuous process where change in plant nutrition brings about
corresponding change in alate production. However, from papers on crowding,
it would appear that alate production is partly a discrete process where
crowding gets to some threshold level (three-four aphids/plant?) and
suddenly alates are produced. From the following examples, it would appear
that crowding is the driving force for alate production while other factors
(e.g. nutrition, parentage, temperature) all modify the magnitude of the
response.
Nutritional stress has been examined by removing aphids from their host
for some period of time and then returning them to their host. This
treatment was applied to adults and nymphs on cotton for 6- to 8-hour
periods each day. Starved nymphs from apterous parents resulted in 13%
alates versus 0.4% from unstarved nymphs. However, starvation of nymphs from
alate parents resulted in no increase in alate formation. A similar result
was also reported for starved parents, where starved apterous parents
produced more alate progeny than well fed apterous parents (23% versus 2%,
respectively), and there was no increase in alate formation by starved alate
parents. The effect of starvation also was detectable in progeny from aphids
starved as nymphs but fed normally as adults (Reinhard 1927). However, this
might be a crowding response if the aphid is interpreting physical contact
with the brush (used to remove the aphid from the plant) as contact with
other aphids.
Nutritional factors from other sources also play a role. One of the more
interesting hypotheses is the possible role of aphid borne plant viruses.
The survival of the virus is dependent on having an efficient aphid vector,
and the most efficient vector is alate. Therefore one might expect that a
virus would promote conditions favoring alate production in the aphid. Alate
production in the melon aphid-zucchini-zucchini yellow mosaic virus system
appeared to increase on infected plants. Unfortunately, virus infected
plants also had more aphids. The authors discuss this and decide that
nutritional factors are the cause for increased alate production (Blua 1991,
Blua and Perring 1992a). To further support the authors' argument that the
cause might be nutritional, it has been shown that aphid infestations on
Solanum integrifolium change peroxidase, esterase, and protein content of
the plant in proportion to the level of infestation (Owusu et al. 1994a).
This shows a change in plant nutrient content associated with aphid density
which might form a chemical link between nutrition and alate production.
Obviously, more work in this area is required.
Crowding effects have been conclusively demonstrated for this aphid on
cotton. One study examined crowding using leaf disks with a single apterous
aphid which was removed following reproduction. The resulting colonies
contained from one to seven nymphs. From 52 colonies with one or two nymphs,
no alates were produced. From 41 colonies with three or four nymphs, less
than 10% of the colony became alate. However, of 29 colonies with five to
seven nymphs, over 30% of the total number of aphids became alate (Graham
1968). This experiment was repeated as part of the control for another
experiment by the same author. Two possibly significant differences were
apparent: alate production only occurred in colonies with four or more
nymphs, and colonies with five to seven nymphs only produced 12% alates
(Graham 1968). The observation that solitary individuals never develop
alates was reported earlier for the melon aphid (Reinhard 1927).
Crowding parents also influenced alate development in the progeny.
Regardless if the parents are crowded or not, colonies with fewer than three
aphids did not develop alate individuals. In colonies with more than three
aphids, the progeny from crowded parents developed more alates than did
progeny from uncrowded parents (Graham 1968).
Parentage also influenced alate production. Apterous aphids can be
reared through 59 generations on cotton with nearly no alate production
(1066 aphids reared, with only 17 alates). The author attributed the few
alates produced to accidental crowding (Reinhard 1927). Uncrowded conditions
were maintained as one aphid per plant. This author tried rearing a
continuous line of alate aphids, where alate parents produce alate progeny
to provide the alate parents of the next generation. The progeny from a
single alate for five generations (59 nymphs) did not produce a single
alate.
Abiotic factors could also influence alate production; temperature and
light being the two obvious signals used as indicators of seasonal change.
However, to date no one has effectively studied these factors. The closest
is the paper by Reinhard (1927), but his research in this area was
inconclusive. There was also a note which reported sexual morph (winged)
development due to short-day conditions ( 10.5 light: 13.5 dark at about
20°C) (Guldemond et al. 1994).
Color Variation. Yellow and a "green that is almost black" form the
extremes of a continuous gradation in color. The yellow form occurs during
warmer summer conditions and is smaller. The green form is larger and occurs
during cooler spring and fall temperatures, and uncrowded conditions. Color
is not a host race trait because color morphs are able to produce progeny of
the other color morph (Setokuchi 1981, Wall 1933). Host plant also
influences aphid color (Regupathy and Jayaraj 1973). Wall (1933) reported
green morphs produced more alate offspring than yellow morphs. However, his
observation could be the result of crowding, as the green form also produced
more total offspring. Since stresses like crowding, higher temperatures and
host plant stress result in a greater proportion of the yellow morph, it was
thought that the yellow morph was a stress induced response. However, some
insecticides can reverse this response. LC
10
doses of sulprofos (a stress)
produced more dark individuals than either the control or LC
10
doses of
cypermethrin or dicrotophos (Kerns and Gaylor 1992).
Abiotic Environment. One of the most important abiotic factors affecting
the life cycle of this aphid is temperature. A lower developmental threshold
for this aphid was estimated at 7.34°C on squash in Taiwan (Liu and Perng
1987). Development thresholds have also been estimated for the aphid on
cucumber as 5.8°C from birth to age of first reproduction, but the
development threshold for the nymphal stages was 6.9°C (Kocourek et al.
1994). A study of this aphid on Veronica persica estimated a developmental
threshold of 10.47°C for the teneral preflight period (Nozato 1989b). An
upper limit to survival of 35°C was reported on squash in Saudi Arabia, but
the authors pointed out that the aphid survives in okra fields where the
daytime temperature exceeds 45°C (Aldyhim and Khalil 1993). Temperature is
also thought to be responsible for some strains of A. gossypii being
holocyclic while others anholocyclic. A hypothesis was that eggs will be
produced in locations where the average temperature during November does not
exceed 13°C (Inaizumi 1980).
Light intensity and day length are also important abiotic factors in the
reproductive capacity of this aphid. Increasing day length from 6 to 12 to
18 hours significantly increased the intrinsic rate of increase, decreased
population doubling time, and decreased generation time. However, longevity,
and R
o
were maximized at a 12-hour day (Aldyhim and Khalil 1993). Another
paper reported A. gossypii subjected to longer days (8 versus 16 hours) and
increasing light intensities (800, versus 4000, versus 8000 lux) had
increased reproduction on cucumber at 18°C with the intrinsic rate of
natural increase doubling from 0.22 to 0.44 (Wyatt and Brown 1977).
Auclair's (1967a) results regarding light intensity conflict with the above
results. Auclair reports that high intensity light (550 lux or brighter)
inhibits feeding and colonization, and aphids feeding on diets exposed to
550 lux would move to diets exposed to 54 lux. There was no obvious
reconciliation between these two studies other than to suggest that
different clones may respond differently to light intensity, or the
difference was due to experimental conditions.
The effect of light intensity may be strong enough to result in
detectable differences under field conditions. In experimental plots in
Texas (USA), cotton was mulched with wheat straw, or left bare ground. In
most cases the mulched plots had fewer aphids. The mulch was reflective, so
the undersides of leaves received significantly more light in the 340-1067nm
range (Rummel et al. 1995). However, more experiments should be done in this
area before assuming a cause and effect relationship.
BEHAVIOR
Flight. Flight is the beginning of the dispersal or sexual reproductive
phase in this aphid's life cycle. It begins with the preflight period (from
molt to flight) which lasts from 1 to 31 hours with most activity between 10
and 24 hours after molt from colonies reared on Veronica persica (Nozato
1987b). The teneral preflight period increased from 10 to over 70 hours with
decreasing temperatures from 28° to 12°C (Nozato 1989b). Adults flew from
about sunrise to early afternoon, but a few individuals continued to fly
after dark. With first light at 0600 hours, and last light at 1930 hours, no
aphid flight was detected from 2300 hours to 0700 hours. Considering that
the time of molting is independent of time of day, the most common duration
of the teneral preflight period is explained by adult inactivity after dark
(Nozato 1987b, Nozato 1989b).
In laboratory colonies, the flight period lasted from 1 to 4 days
(Nozato 1990). Older colonies produced fewer alates that flew for one day
and more that flew for two days. Aphids flew from one to several (about
five) times each day, with the first flight always longer than the others.
Alates larviposited after flight, and flew again when the number of embryos
with pigmented eyes per ovariole decreased. Alates that flew longer had a
shorter reproductive period and produced fewer total progeny. Forewing
length, teneral period, and first flight duration did not influence the
flight period (Nozato 1987b). Two authors reported that alates will not
produce offspring on leaves with existing colonies (Nozato 1989a, Reinhard
1927).
Migration. In cotton fields in the Ivory Coast, dispersal from savanna
to cotton fields was examined for A. gossypii from data collected using pan
traps (Duviard et al. 1976). These data showed that most aphids settled at
field margins, although there was some settlement in the field. They also
reported that pan traps at ground level caught more A. gossypii than traps
further from the ground. From their graphs, it appears that most aphids were
caught no more than 1 meter from the soil surface, and that the closer to
the surface, the more aphids were caught.
Light. This aphid is sensitive to different wavelengths and intensities
of light, but the nature of the effect is not clearly understood. Aphids
were attracted to Auclair's diet illuminated at 570-595 nm while diets
illuminated at 420-485 nm were repellent (Auclair 1967a). This contradicts
other findings where newly molted alate adult individuals preferred shorter
wavelengths down to 357 nm. Adults of mixed age also preferred this short
wavelength, and their preference declined with increasing wavelength.
However, there was an increase in preference beginning at 547 nm, peaking at
562 nm, and rapidly declining after the peak (Pospisil 1971). This peak is
approximately where Auclair (1967a) did his studies, and could explain the
different results. Furthermore, there is a stage dependent response to
light, adults being more sensitive to different wavelengths than nymphs
(Auclair 1967a). In keeping with these results, Rummel et al. (1995)
reported fewer aphids in cotton plantings with wheat straw mulch, and light
in the 420 to 485 nm wavelength was significantly higher in the mulched
plots.
Host Plant. Orientation to host plants was significant at 6 hours after
wing development, but was highly significant after 24 hours . Alates were
able to distinguish between different plants; Cucurbita pepo and Thunbergia
laurifolia were attractive, and were common hosts for this aphid in Cuba.
The occasional host Hibiscus rosa-sinensis L. was neither attractive nor
repellent, and the non-host plant Lantana camara L. was repellent (Pospisil
1972).
In addition to the type of host present in a field, the arrangement of
hosts within the field is also important. An experiment was done using
soybean, dwarf sorghum and tall sorghum planted in monoculture or
interplanted. At the sorghum canopy level, landing rates were highest on
monocultures of dwarf sorghum, then monocultures of tall sorghum, and lowest
in mixed plantings. This difference was attributed to a lower percentage
ground cover in monocultures. In mixed fields, landing rates were equal in
dwarf sorghum and soybean, but in tall sorghum interplanted with soybean the
aphid preferred to land on soybean (Bottenberg and Irwin 1992).
Feeding: In one set of experiments, alates were placed on Cucurbita pepo
plants and watched under a microscope. Given that probing occurs when aphids
pressed their labium to the surface, and placed their antennae flush with
the body, the aphid took 6 to 9 minutes following contact with the plant
before probing (Yuan and Ullman 1996). However, this is the time it took
newly emerged alates, and may not be characteristic of alates after
migration.
Egg Laying. Egg laying on H. syriacus occurred mostly between the leaf
scar and the twig near where the buds would emerge in spring. Some eggs were
also laid at the branching point of twigs. However, from the wandering
behavior of the oviparous females, it appears that females searched for
protected places to lay eggs rather than for specific parts of the plant
(Inaizumi and Takahashi 1989b).
Virus Interaction. Two papers deal with the effect of viral infection of
host on the aphid. The first reported that aphids on Yellow-Vein Mosaic
Virus infected okra did not reproduce as fast as aphids from healthy okra
(Regupathy and Jayaraj 1972). A possible mechanism for the observation was
provided by another author using Zucchini Yellow Mosaic Virus infected
zucchini (Cucurbita pepo) plants (Blua and Perring 1992b). Aphids on
infected plants spent more time probing and less time feeding than aphids on
healthy plants. Furthermore, prior to feeding, aphids on infected plants
spent more time in forming the salivary sheath.
Within Plant Distribution. On cotton grown in the former Soviet
Socialist Republic, A. gossypii migrated from the stem apex to the upper
leaves and then to the lower leaves in the morning (Tshernyshev et al.
1981). During the day, aphids were mostly on the underside of leaves, and
they migrated back to the stem apex at night. The table in Tshernyshev et
al. (1981) indicated that many individuals did not conform to this pattern.
In eggplant from India, the aphid settled on older mature leaves. It moved
to younger tissues only when population pressure forced it to so aphid
populations were always greatest on older leaves (Banerjee and Raychaudhuri
1985). In cantaloupe (Cucumis melo L.) from the USA, the aphid was most
abundant on the basal portion of vines (Edelson 1986). In cotton in the USA,
the aphid was most abundant in the middle canopy, followed by the upper
canopy. However, this pattern may be a result of high aphid mortality from a
fungal pathogen in the lower canopy rather than a result of aphid behavior
(O'Brien et al. 1993). Other authors in the USA have related aphid density
to leaf age and mostly report larger populations on older leaves (Hardee et
al. 1994, Slosser et al., in press). However, year to year variability in
location of the highest aphid population has been reported (Slosser et al.,
in press) and the aphid's preference may change through the season. In
Greece, aphids infested the top of the cotton plant early (May-June) and
late in the season (October), but preferred the lower parts during the
middle of the season (July-August) (Kapatos et al. 1996).
BIOCHEMISTRY
Genetic Characters. Khuda-Bukhsh and Datta (1978) reported that in A.
gossypii 2n=8 (found on Ageratum conyzoides L. (Asteraceae) in India). The
chromosomes in cells during metaphase measured 2.3, 3.4, 3.8, and 5.0 µm in
length. Using aphids from a different location Khuda-Bukhsh and Pal (1985)
reexamined the karyomorphology of this aphid and reported that chromosome
lengths were 3.65 ± 0.54, 5.42 ± 0.44, 6.24 ± 0.48, and 7.64 ± 0.85 µm
(collected from Erobtorys japonica (Rosaceae) in India). These authors
provided further discussion of the processes occurring during cell division.
Khuda-Bukhsh and Kar (1989) reported differences in chromosomal length
within each pair of chromosomes. They reported chromosome lengths of 2.00,
2.25, 3.55, 3.80, 4.00, 4.50, 6.45, and 6.80 µm. The chromosomes are
believed to be holokinetic which could simplify structural rearrangement of
chromosomes, and permit more rapid adaptation to adverse conditions,
including new host plants. This mechanism for adaptation has been shown in
Myzus persicae. Chromosomal rearrangement in M. persicae is one source of
pesticide resistance (Blackman et al. 1978). The effect appeared to be due
to a translocation that was correlated with an increase in carboxylesterase
(est-4) activity.
Another method for evaluating DNA, random amplified polymorphic DNA
polymerase chain reaction (RAPD-PCR), can detect differences in A. gossypii
colonies (Cenis et al. 1993, Ebert 1994) and between the melon aphid and
other aphid species (Cenis et al. 1993). Differences in A. gossypii DNA
occurs between aphids feeding on different host plants (Ebert 1994, Khuda-
Bukhsh and Kar 1989), but neither reported conclusive evidence that the
differences were due to mutation rather than selection of adaptable strains
within a parent population.
Host Adaptation. A. gossypii requires time to adapt when switching
hosts, or feeding on artificial diet. Knowing the duration of this
adaptation period is critical in biological and nutritional studies because
during this period the response of the aphid is a combination of the effect
of the new host and a stress response. Field collected aphids from various
cucurbits could adapt to a susceptible muskmelon line in 6 months, as
measured by an increase in the reproductive rate (Kishaba and Coudriet
1985). Another author reported that the aphid would not adapt to a new host
in 3 months in experiments transferring clones between plants in the
Cucurbitaceae and Solanaceae (Saito 1991). Aphids transferred between
cucumber and chrysanthemum began to adapt to the new host (as measured by
adult weight and development time), and if transferred back to their
original host, they did not return to original conditions within three
generations (Guldemond et al. 1994). Aphids have also been transferred from
plants in the Cucurbitaceae to wheat. While the transfer was successful, the
reproductive rate on wheat never achieved that on the cucurbits even after 2
years (Ebert 1994). However, the aphids had probably adapted to wheat as
much as their genotype would permit without mutation.
Since different host plants contain different secondary compounds, one
might expect that aphids adapted to different hosts would show different
enzyme levels. Furthermore, these levels should change when the aphid was
switched to a new host. However, one study failed to show this phenomenon
with aphids adapted to eggplant, cucumber, taro, or watermelon. The enzymes
examined were malic enzyme, phosphoglucomutase, glucosephosphate isomerase,
6-phosphogluconate dehydrogenase, isocitrate dehydrogenase, malate
dehydrogenase, esterase, and carboxylesterase. The only difference in the
colonies was reported for aphids on taro for malate dehydrogenase (Owusu et
al. 1996). This lack of observable differences may be due to using only
insecticide resistant aphid clones from each colony. This was done to try
and remove effects of past field exposure to insecticides from the results
of the experiment. However, this may have also removed much of the natural
enzyme variability in the aphid populations.
Insecticide Response. Aphids reared on different plants show different
levels of susceptibility to insecticides (see McKenzie and Cartwright 1994).
Several mechanisms for resistance have been demonstrated in this aphid:
enzymatic differences, target insensitivity, cuticular modifications, and
life history modifications at the population level. However, studies in this
area suffer from an inability to differentiate between phenotypic plasticity
versus differences in aphid genotype as selected by host plant. Confounding
the entire issue is the effect of host plant response to insecticides,
either through metabolism of the insecticide or insecticide induced changes
in plant nutrient levels.
In some cases, pesticide resistance in this aphid was correlated with
different aliesterase levels in aphids on different host plants. Aphids
reared on melon or cucumber showed elevated aliesterase levels relative to
aphids from eggplant or potato (Saito 1991). Aphids with high aliesterase
activity maintained original levels of aliesterase activity even when moved
to solanaceous crops, and aphids with low aliesterase activity maintained
low levels when moved to cucurbitaceous crops. This represents a difference
between two strains of this aphid correlated with a difference in host
plant, and is clearly not host induced. Other authors also have reported
significant differences in esterase patterns and esterase quantity, and have
correlated these differences with insecticide resistance (Furk et al. 1980,
Hama and Hosoda 1988, O'Brien 1992, O'Brien et al. 1992, Saito et al. 1995,
Takada and Murakami 1988) and with host plant preference (Furk et al. 1980).
While mixed function oxidases (MFOs) may play a role in detoxification
reactions, the esterases and carboxylesterases showed more conspicuous
differences between susceptible and resistant aphid strains (Sun et al.
1987).
Feeding is one method for insecticide entry into the aphid. Peroxidase
levels in salivary glands, sheath material, and salivary excretions of A.
gossypii might play some role in detoxifying systemic insecticides. For this
reason, the role of salivary gland enzymes in detoxification has been
examined as a possible defense. While the peroxidases were effective in
detoxifying hordenine and gossypol (secondary plant compounds in cotton),
the role of these enzymes in the natural habitat of the aphid is not clear
(Miles and Peng 1989).
This aphid also acquires resistance through target site insensitivity
and through increased production of the affected enzymes.
Acetylcholinesterase (AChE) insensitivity was shown in aphids resistant to
organophosphate and carbamate insecticides (Moores et al. 1988).
Furthermore, activity level of acetylcholinesterase has been correlated with
pirimicarb resistance (Gubran et al. 1992, Silver et al. 1995, Suzuki and
Hama 1994). For two clones, this resistance was shown to be specific to
pirimicarb (Silver et al. 1995). These clones were 800 fold more resistant
than the susceptible clone, but no more than 22 times more resistant to six
organophosphates, six carbamates, and two pyrethroids. The mechanism was
linked to AChE with higher catalytic activity and lower affinity to
pirimicarb in the resistant clones. Cuticular differences as well as
acetylcholinesterase insensitivity played a role in insecticide resistance
in parathion and paraoxon (Sun et al. 1987).
In studying the cause for a control failure in cotton (USA) the
biological cost of resistance for an organophosphate resistant aphid feeding
on cotton was estimated. Over the first few days resistant alate aphids
produced more progeny, but over the life span of the adult there was no
significant difference between the resistant and susceptible aphids.
However, as these authors point out, reproductive rate during the first few
reproductive events are the most influential in determining population
growth rate (O'Brien 1992, O'Brien and Graves 1992). These authors proposed
that the organophosphate insecticide had selected for individuals with
higher initial reproduction, as opposed to stimulating reproduction (O'Brien
and Graves 1992).
Life stage is another factor affecting the susceptibility of this aphid
to insecticides. Alate adults on cotton were more resistant than apterous
adults to oxydemeton-methyl, chlorpyrifos, dicrotophos, biphenate, and
endosulfan (Grafton-Cardwell 1991).
Pest resurgence is where a pesticide treatment causes some mortality,
but ultimately results in much higher pest populations. Pest resurgence can
be due to the action of pesticide on the insect, the action of pesticide on
the plant, the action of pesticide on natural enemies, or some combination
of the three. Classical thought attributes most or all of pesticide
resurgence to a reduction in natural enemies. However, under field
conditions it is difficult to control for other factors, and they are often
ignored. However, a few authors have examined these other factors. Sulprofos
treated cotton fields had elevated numbers of A. gossypii, but the cotton
plants in these fields had significantly elevated levels of threonine and
"essential" amino acids (Kerns and Gaylor 1993). Cotton plants treated with
the systemic insecticides disulfoton, phorate, dimethoate, and lindane had
larger aphids, but treated plants had lower sugar content, lower nitrogen
content, lower carbohydrate to nitrogen ratio, and higher amino acid content
(Sithanantham et al. 1973). Okra treated with phorate had more aphids which
were also physically larger, but the phorate treatment also resulted in
elevated levels of NH
4
nitrogen, potassium, and a decrease in carbohydrates,
magnesium, and calcium (Regupathy and Jayaraj 1974b). Although altered plant
physiology may account for aphid resurgence in some cases, it is not the
only cause. Direct applications to the aphid of deltamethrin, methyl
parathion and carbaryl stimulated the reproductive rate of A. gossypii. Some
of this effect was due to elevated feeding levels at LC
10
doses of
deltamethrin and methyl parathion (Gajendran et al. 1986). Other authors
also reported elevated aphid populations following pesticide applications,
but did not examine causes (Patel et al. 1986, Surulivelu and Sundaramurthy
1986, Thimmaiah and Kadapa 1986).
Host plant mediated susceptibility to DDT, lindane, endrin, endosulfan,
malathion, ethyl parathion, methyl parathion, dimethoate, phosphamidon, and
carbaryl was reported for aphids reared on six cucurbitaceous hosts (Juneja
and Sharma 1973). Aphids on cucumber were consistently less susceptible to
all insecticides relative to aphids from the original culture on bottle
gourd (Lagenaria siceraria (Molina) Standl.). Other than this, there was no
consistency in the level of resistance and host plant. Based on relative
toxicity within each host plant, phosphamidon was most toxic followed by
methyl parathion, while p,p' DDT was least toxic. The toxicity rank of the
other pesticides changed depending on host plant (Juneja and Sharma 1973).
Aphid colonies feeding on watermelon versus cotton showed differences in
pesticide susceptibility between bifenthrin, chlorpyrifos, dicrotophos,
dimethoate, endosulfan, methomyl, and oxydemeton-methyl (McKenzie and
Cartwright 1994). An interaction between host plant resistance and pesticide
resistance in this aphid can also occur. A. gossypii reared on aphid
resistant chrysanthemums showed increased susceptibility to parathion or
nicotine relative to aphids on a susceptible cultivar (Selander et al.
1972). However, plants producing more detoxifying enzymes (esterases and
transferases) in response to insecticides may help aphids by metabolizing
insecticides. While a cause and effect relationship could not be proven,
there was good correlation between plant enzyme levels and reduced aphid
mortality from dichlorvos on okra, cucumber, and eggplant (Owusu et al.
1995).
Aphid Nutrition. Aphid nutrition has been studied by stressing the host
plant or using holidic diets. Cotton plants in Arkansas were grown in the
greenhouse in sand fertilized with solutions containing 10% of the nitrogen
or 5% of the potassium of the full fertilizer (Isely 1946). Aphis gossypii
took longer to mature, and had a lower larviposition rate on nutrient
stressed plants, but only nitrogen stressed plants produced a significant
reduction in total offspring and total duration of reproductive period. The
effect of nitrogen fertilization was also examined on cucumber using
hydroponically grown plants (Petitt et al. 1994). As expected, these authors
showed differences in aphid population growth correlated with nitrogen level
in the solution. The importance of fertilizers, especially nitrogen, was
also recorded for this aphid feeding on eggplant in West Bengal (Banerjee
and Raychaudhuri 1987), potato in Egypt (El-Saadany et al. 1976), cotton in
USA (Beckham 1970, Slosser et al., in press), and cotton in Egypt (Rasmy and
Hassib 1974). However, it is not always possible to detect the effect of
fertilizer on aphid populations in the field (Slosser et al., in press).
Another way to change nutrient quality of the host is to limit the
availability of water. On cotton, alate aphids did better on leaves with sap
densities under 11%, and such leaves occur on the lower part of the plant
during flowering (Weismann et al. 1970). Another study on cotton reported
that total leaf water content was positively correlated with higher aphid
numbers, and lower leaves on cotton have a higher water content (Slosser et
al. 1992). It is unclear if water content is the cause for greater aphid
numbers on lower leaves, or if cotton aphids prefer lower leaves for other
reasons.
While water content may play a role in aphid fecundity, other changes in
the plant associated with water balance also influence aphid populations.
Aphid population density increased on potted cotton plants as the frequency
of watering decreased from once every 3 days to once every 6 days to once
every 9 days. The cause was attributed to an observed increased plant
nitrogen levels and decreased carbohydrate levels in the foliage associated
with decreased watering (Hassib and Rasmy 1974). A different study examined
levels of carbohydrate, nitrogen, fat, sterol, and inorganic salts in
eggplant, and reported that only nitrogen levels were significantly
correlated with aphid populations (Banerjee and Raychaudhuri 1987). Thus,
some of the effect of plant drought on aphids may be due to altered
nutritional status, but sap density and microclimate changes associated with
altered canopy structure are confounding factors (e.g., wilting) (Weismann
et al. 1971).
A popular method of studying aphid nutrition is to use artificial diets.
So far, no diet has been reported which will indefinitely support A.
gossypii growth and reproduction. At most, only two generations survive,
which is insufficient time for the aphid to adapt to the diet. Therefore,
the following reports are subject to alternate interpretation based on
stresses from as yet unidentified sources. The authors of the papers
recognize this problem. For this discussion, I treat the nutritional
requirements of the aphid as the aphid plus its symbionts.
An artificial diet for the pea aphid was developed by Auclair in 1965
which has been used for A. gossypii (Auclair 1965). Aphids transferred to
the artificial diet survived, and produced progeny, but the progeny produced
by these aphids did not survive (Auclair 1967b). On this diet, the growth
and birth rate of A. gossypii was highest on diet adjusted to pH 7.4-7.8
(Auclair 1967b). The importance of sugars, both nutritionally and as
phagostimulants, are well known. The optimal sucrose concentration for
settling was 40%, but the optimal sucrose concentration for growth and
reproduction was 20 to 30% (Auclair 1967a). Diets with some or all sucrose
replaced with one of the following, raffinose, sorbose, melezitose,
glactose, lactose, ribose, or cellobiose, were less suitable than diets with
only sucrose (Auclair 1967a). The diet consisting of 20% sucrose and 10%
maltose yielded progeny with significantly higher biomass, and more total
progeny in the second generation. However, by all other measures this diet
was either equal to or inferior to the other diets. These measures include
mean adult weight, lifespan, progeny of the first generation, progeny
produced per day, and settling of larvae and adults on the diet (Auclair
1967a).
The nutritional requirements of A. gossypii were examined by Turner
(1971, 1977) using the diet developed by Auclair. Diet was evaluated using a
growth index that was a function of the total aphids produced in 6 days and
the weight of those aphids. Better diets were identified by having a higher
growth index. Both cysteine and methionine are required for maximum growth.
Concentrations of either amino acid above 30 mg/ml are toxic. Inorganic
sulfur, as sodium sulfate or ammonium sulfate, does not substitute for these
amino acids when present in equivalent molar concentrations to the amino
acids. While the concentration of methionine is sufficient in Auclair's
diet, Turner recommends 700 mg more cysteine be added. Turner also altered
concentrations of tyrosine, phenylalanine, and tryptophan from Auclair's
diet. He shows that aphids continue to reproduce on diets lacking all three
amino acids, but the aphid does better with them present. Phenylalanine
concentrations from 0 to 8 mg/ml were examined, and the aphids did best at 2
mg/ml. Tryptophan concentrations from 0 to 8 mg/ml were examined, and the
aphids did best at 4 mg/ml. Tyrosine concentrations from 0 to 0.40 mg/ml
were examined and the aphids did best at 0.4 mg/ml. All of these represent a
recommended increase in the concentrations from the original diet.
PLANT DEFENSES
Among the factors determining host range of phytophagous insects are
plant defenses. These can be mechanical or chemical, and the insect must
overcome these defenses in order to survive and reproduce. The main
characteristic implicated as a physical mechanism of defense is leaf
trichome density. Glabrous cotton supported fewer aphids than more pubescent
cotton (0.52, 2.34, 4.48, and 6.09 hairs/mm
2
) (Dunnam and Clark 1938, Rummel
et al. 1995, Weathersbee III et al. 1994). However, pubescence has the
opposite effect on this aphid feeding on muskmelon (Kennedy et al. 1978).
Leaf color may also have some effect. The red and yellow isolines of TM-1
cotton (USA) had fewer aphids relative to the TM-1 isoline with green leaves
(Rummel et al. 1995).
Many crops have some level of physiological resistance to this aphid
that can be classified into one of three categories: tolerance, antixenosis,
or antibiosis. The causes for resistance were examined in muskmelon and
cucumber. Resistance has also been documented in the following crops: okra
(Gunathilagaraj et al. 1977, Uthamasamy et al. 1976): Gossypium hirsutum and
Gossypium arboreum (Chakravarthy and Sidhu 1986); Antigastra catalunalis
(Muralidharan et al. 1977); Citrullus lanatus (MacCarter and Habeck 1973);
Solanum melongena (Sambandam and Chelliah 1970); and Colocasia esculenta.
(Palaniswami et al. 1980).
Muskmelon. All three mechanisms of plant resistance (tolerance,
antibiosis, antixenosis) have been documented for muskmelon. In some
muskmelon, several genes confer tolerance by reducing the curling response
of leaves subjected to heavy feeding. There appeared to be a single gene
controlling the curling response of the plant to aphid attack (Bohn et al.
1973). Resistance in Cucumis melo can also be due to antixenosis (Kennedy
and Kishaba 1977). The effect remained in excised leaves for at least 4
days. It was not translocatable across a graft union. In some muskmelon,
antixenosis was caused by a single dominant gene with a few other genes
playing a minor role (Kishaba et al. 1976). Antibiosis has also been
reported as a source of resistance in muskmelon. Electronic recording of
aphid feeding showed that aphids feeding on resistant plants made fewer
contacts with the phloem, and the duration of each feeding episode is two to
three times shorter on resistant plants. However, aphids on the resistant
plants made more contacts with the phloem. Physical examination of the
stylet sheaths showed an increase in the proportion of branched stylet
sheaths, and an increase in the number of branches per stylet sheath.
However, contrary to the electronic recording, histological evidence
suggested that the aphids contacted the phloem less in the resistant plant.
Furthermore, while there was no difference in the number of stylet sheath
branches ending in xylem, palisade, bundle sheath or epidermis, there were
significantly more which ended in the mesophyll. The discrepancy between the
electronic recording of aphid feeding and the histological evidence was
attributed to the histological evidence looking at a fixed instant in time
while the electronic recording includes a time component (Kennedy et al.
1978).
Cucumber. The Bi gene permits cucurbitacin production in cucumbers.
Aphids on non-bitter Cucumis sativus had a higher average daily reproductive
rate, and achieved much higher densities than aphids on bitter plants.
However, aphids on bitter plants had a shorter development time (Haynes and
Jones 1975).
Tissue age plays a significant part in host plant resistance. In
cucumber, aphids on older leaves had 82% nymphal mortality versus less than
25% on middle aged and young leaves (van Steenis and El-Khawass 1995).
Aphids on older leaves also had reduced fecundity - 45.9 nymphs/female on
lower leaves versus 70 nymphs/female on middle and young leaves. In
chrysanthemum, the effect of leaf position was determined by cultivar
(Storer and van Emden 1995). Survival was unaffected by position in two of
the three cultivars (Hero and Purple Anne) and highest on lower leaves in
cultivar Surfine. Development time, fecundity, and the intrinsic rate of
increase (r
m
) were more favorable (when significant) for rapid population
growth on lower leaves (Storer and van Emden 1995). The effect of tissue age
was reported for cotton in field trials where planting date interacted with
season to significantly alter aphid populations (Slosser et al., in press,
Slosser et al. 1992).
VIRAL INTERACTIONS
The most important impact that A. gossypii has on world agriculture is
through its ability to transmit plant viruses. Table 2 lists plant viruses
transmitted by this aphid. The list does not contain older references
because of problems in proper identification of the aphid and the viruses;
see Kennedy et al. (1962) for older references.
The type of transmission is classified as persistent, semipersistent,
and nonpersistent using a system first proposed by Watson and Roberts (1939)
and later modified by Sylvester (1956). Pirone and Harris (1977) recommend
the use of stylet-borne and circulative to categorize aphid borne viruses.
However, we have retained the old system because most of the literature uses
the old system, and in many cases it is not known if the virus is stylet-
borne or not.
This review proposes that the plant-aphid-virus system be thought of as
a series of simple effects (e.g., aphid population growth, plant growth,
virus replication) plus a series of interactions (e.g., "plant x aphid",
"plant x virus", "aphid x virus", and possibly the three way interaction).
Breeding plants resistant to virus modifies the "plant x virus" interaction.
The "plant x virus" interaction could occur by a modification of leaf
cuticle hydrocarbons. This could have the same effect as spraying the crop
with oil which has been shown to decrease transmission of non-persistent and
semi-persistent viruses (Singh 1981, Vanderveken 1977). Modifying other
interactions will also reduce the incidence of disease. Documenting which
effect is responsible for any observed reduction in disease incidence is
important for properly evaluating the results. For example, the "aphid x
virus" interaction can occur if the virus coat protein changes (Gera et al.
1979). One would also expect that this could occur if the binding sights on
the aphid were to change, but this has not yet been demonstrated. The "plant
x aphid" interaction is exemplified by plants which are repellent to
insects, or lack cues which the insect uses to distinguish host plants from
non-host plants (e.g., some melons are resistant to virus transmission, but
the cause appears to be due to antixenosis [Pitrat and Lecoq 1980]).
Short literature reviews of citrus tristeza virus, cucumber mosaic
virus, and potyviruses highlight the complex nature of the interactions
possible in plant-aphid-virus systems.
Citrus Tristeza. Citrus tristeza, a member of the closterovirus group,
is a phloem-limited virus attacking plants in the Rutaceae almost
exclusively. It is a filamentous particle 11x2000 nm long. The genome is a
single strand of RNA. Aphis gossypii transmits this virus semi-persistently,
remaining infectious for over 24 hours (Bar-Joseph et al. 1989). The system
was not sensitive to the culture host of the aphid but was sensitive to
temperature (Bar-Joseph and Loebenstein 1973). Different strains of A.
gossypii did not differ in their ability to transmit citrus tristeza, but
different strains of the virus did differ in their transmission rates by
this aphid (Raccah et al. 1980). The aphid acquires the virus more easily
from some citrus cultivars than from others. The acquisition period can be 5
minutes, but was more efficient at periods of 30 minutes to 24 hours.
Infectivity was lost within 48 hours of acquisition, but feeding on
alternate host plants does not reduce infectivity (Bar-Joseph and
Loebenstein 1973). Aphids reared on cucumber were able to acquire the virus
when fed on infected citrus as easily as aphids reared on citrus (Bar-Joseph
and Loebenstein 1973). This was also true of aphids reared on muskmelon
(Cucumis melo L.), and kenaf (Hibiscus cannabinus L.) (Norman and Sutton
1969, Roistacher et al. 1984). Transmission rates were significantly lower
when plants were held at 31°C relative to those at 22°C (Bar-Joseph and
Loebenstein 1973). When the plants were cooled (31° to 22°C), it took about
6 days for an increase in transmission rate. When plants were warmed (22° to
31°C), it took 12 to 20 days for transmission rates to decline. The apparent
reason for this effect was different virus titers in trees at the two
temperatures. The inoculation period should be 4 to 6 hours (Bar-Joseph and
Loebenstein 1973). Aphis gossypii was able to transmit the virus to certain
cultivars more efficiently than to others (Roistacher and Bar-Joseph 1984).
Cucumber Mosaic Virus. Cucumber Mosaic Virus (CMV) is the type member of
the cucumovirus group. The virus is a set of three isometric particles 29 nm
in diameter each consisting of a protein coat built from 180 identical
subunits, and encapsulating four main single stranded RNA molecules, several
minor strands, and a variable number of satellite RNA molecules (molecules
requiring the virus for replication and encapsidation, but unnecessary for
virus function). In order of decreasing size, the major RNA strands are
designated RNA 1, 2, 3, and 4. The minor strands are designated RNA 4a, 5
and 6. The active virus is a set of three distinct particles all of which
must be transmitted for infection; one particle has RNA 1, one particle has
RNA 2, and the third has RNAs 3 and 4. The remaining RNA molecules may or
may not be present (Palukaitis et al. 1992). RNA 1 is necessary for
infection and replication. It also influences symptom severity and rapidity
of expression of the symptoms. RNA 1 also plays a role in aphid transmission
(Francki et al. 1985, Zitter and Gonsalves 1991). RNA 2 is also required for
infection and replication. RNA 3 codes for coat protein, but requires RNA 4
to express the trait. RNA 3 is also necessary for aphid transmission. In
some cases RNA 3 determines the host plant reaction while in others it is
RNA 2, or both (Francki et al. 1985). RNA 4 is generated from RNA 3. RNA 4
is necessary for coat protein synthesis, but not for infectivity.
CMV has the widest host range of any virus, attacking plants from 85
plant families (Palukaitis et al. 1992). It was transmitted non-persistently
on the stylets of the aphid vector. Unlike citrus tristeza, previous host
changes the ability of the aphid to acquire CMV (Jacquemond 1982), and
different aphid clones differ in their ability to transmit CMV (Simons and
Eastop 1970). Acquisition time can be short (under 1 minute), but
transmission rate increases with longer feeding times up to at least 15
minutes (Camino-Lavin 1970). Changes in the virus coat protein can change
the effectiveness of aphids in transmitting the virus (Gera et al. 1979).
Between an aphid transmissible strain (Fny-CMV) and a poorly transmissible
strain (M-CMV), there were eight amino acid changes in the coat protein.
Amino acids 129, 162, and 168 of the coat protein mediate the aphid-virus
interaction, but amino acid 168 plays a relatively minor role relative to
the other two amino acid positions (Perry et al. 1994). Aphids lose their
ability to transmit following probing or after fasting for about four hours
(Simons and Eastop 1970). Transmission rate is dependent on the
concentration of virus in the host. A virulent isolate reproduced faster
than a less virulent isolate in muskmelon with a corresponding increase in
transmission of the more virulent isolate (Banik and Zitter 1990).
An enzyme linked immunosorbant assay (ELISA) has been used to detect CMV
from individual aphids (Gera et al. 1978). The aphid transmissible strain
carried 0.01-0.1 ng of virus per aphid. The non-transmissible strain was not
detectable on the aphid.
Potyviridae. Many members of the potyviridae are transmitted by the
melon aphid. Among the better studied members are: potato virus Y (PVY),
watermelon mosaic virus I and II (WMVI, WMV2), zucchini yellow mosaic virus
(ZYMV), and papaya ringspot virus (PRV). These viruses consist of a flexuous
rod 680-900 nm long and ±12 nm in diameter. The genome is a single molecule
of single stranded RNA (Francki et al. 1985). Unfortunately, no single virus
in this group has been studied extensively in its association with this
aphid. As a result, the following examples are pieced together from articles
each dealing with a different virus in this group. Different aphid life
stages had different vectoring potential of PVY with the adult alate stage
having the lowest transmission efficiency (Singh et al. 1983). Differences
in virus composition in ZYMV changed the ability of the aphid to transmit
the virus (Lecoq et al. 1991). Different clones of the aphid differ in their
ability to transmit PRV (Lupoli et al. 1992). Acquisition and transmission
times for both ZYMV and WMV2 can be as short as 15 seconds (Perring et al.
1992). The host plant phenotype might also be important (Gooding and Kennedy
1985, Simons 1959).
Several conclusions can be drawn about the nature of non-persistent
viruses. From the short acquisition time, it is likely that the source of
the virus is in the epidermis of the host plant (Pirone and Harris 1977);
therefore, the aphid could acquire the virus with only a brief probe. This
hypothesis would be consistent with aphid feeding patterns where many short
probes occur prior to a much longer sustained feeding probe. If aphids are
to acquire the virus in only a few seconds of probing, the virus needs to be
available in the tissues invaded by short probes. This is also consistent
with the observation that starvation increases virus acquisition because
short probes become more frequent following starvation (Powell 1993). It is
also likely that the virus is not just a physical contaminant on the aphid
stylet, but involves a chemical reaction to specific binding cites on some
part of the stylet. If the interaction was just physical, one should not
observe differences in transmission rates from different aphid clones, there
should be no difference in transmission rate between aphid species, and
specific sites in the virus genome should not alter transmission rates.
OTHER BIOLOGICAL INTERACTIONS
This section deals with other organisms which influence aphid survival.
This is not intended to be a review of these other organisms other than as
they affect A. gossypii. In general, these studies have concentrated on the
biology of the other organism. This trait is reflected in the following text
on the ecological relationship other organisms have with the aphid, but the
emphasis of some papers was changed from that provided by the original
author.
Ants. A beneficial effect to the aphid of the presence of ants
Camponotus japonicus Mayr was reported from research in Japan (Nozato and
Nagano 1988). Aphid populations tended by ants increased in spite of the
presence of the coccinellid predator Coccinella septempunctata bruckii L.;
however, the level of protection afforded by the ant was highly variable. A
positive correlation between A. gossypii, its coccinellid predator
Menochilus sexmaculatus (Fabrecius), and the ant Camponotus compressus
Fabrecius was reported from a guava (Psidium sp.) orchard in India. However,
there was a negative correlation between ant abundance and coccinellid
abundance. The cause for this effect was not investigated, and it was
unclear what effect this had on aphid densities (Verghese and Tandon 1987).
Laboratory studies on cotton in the USA examined the effect of Solenopsis
invicta Buren on the predators Hippodamnia convergens Guerin-Meneville,
Chrysopa carnea Stephens, Scymnus louisianae Chapin, and Syrphus sp. feeding
on A. gossypii (Vinson and Scarborough 1989). With ants present, all
predators except Syrphus were unable to control aphid densities. Without
ants all predators were able to control aphid densities.
Predators. The effectiveness of predators is highly variable depending
on availability of alternate prey, host plant, and environmental factors.
The effect of alternate prey was reported for Chrysoperla rufilabris
(Burmeister) which preferred Helicoverpa (=Heliothis) virescens (Fabrecius)
larvae to aphids, but preferred aphids to H. virescens eggs (Nordlund and
Morrison 1990). Presence of A. gossypii was shown to decrease predation on
H. virescens eggs by the following predators: Hippodamnia convergens,
Chrysopa carnea, and Orius insidiosus (Say) (Ables et al. 1978).
Syrphid flies have shown potential in controlling aphid populations
under greenhouse conditions (Adashkevich and Karelin 1988, Babayan and
Hovhannisian 1984, Chambers 1986). However, colonization by the syrphid was
decreased on older plants, and older larvae would not transfer from young
plants to more mature plants (Adashkevich and Karelin 1988). The suggested
cause for the latter effect was leaf pubescence.
From the many studies on aphid predators, it is obvious that these
organisms can regulate aphid populations under the right circumstances.
However, while most reports deal with a single predator, there are a complex
of predators in the field. One paper reported on interactions of several
predators of this aphid (Rosenheim et al. 1993). The lacewing Chrysoperla
carnea (Stephens) was able to cause an overall reduction in aphid abundance
when caged on field grown cotton in California. Added to this system were
several hemipteran generalist predators (Geocoris spp., Nabis spp., and
Zelus spp.) which feed on the aphid, lacewing, and each other. As expected,
all of these predators reduced aphid populations, though none were as
effective as C. carnea. However, all of the hemipterans also reduced
lacewing survival which resulted in an increased number of aphids.
Furthermore, the reduction in the ability of lacewings to control aphid
populations was increased with increasing size of the other predators.
Parasitic Hymenoptera. Changes in parasitism based on age structure of
A. gossypii populations feeding on cotton were reported for the parasites
Trioxys spp. and Aphelinus sp.. These parasites rarely parasitised first-
and second-instar aphids. Thus, the percentage parasitism increased as the
proportion of older aphids increased (Luo and Gan 1986). This has survival
value for both parasite and aphid because aphids parasitized as older nymphs
or as adults have a chance to reproduce. Aphids parasitized by Aphidius
colemani Viereck had a fecundity of 0.5-1.3 nymphs/female when parasitized
in the fourth instar, and 10.5-13.3 when parasitized as adults (van Steenis
and El-Khawass 1995). Aphids which survived an attack had lower fecundity
but equal longevity relative to unattacked aphids (van Steenis and El-
Khawass 1995).
Hyperparasitization by Alloxysta pleuralis (Cameron) of the primary
parasites Lipolexis scutellaris Mackauer, and Trioxys indicus Subba Rao &
Sharma parasitizing A. gossypii was reported from research conducted in
India. There was significant decline in rates of hyperparasitization of T.
indicus parasitizing A. gossypii feeding on solanaceous crops (Capsicum
frutescens L., and Solanum melongena) versus crops in the Fabaceae (Cajanus
sp., Dolichos sp.), and Cucurbitaceae (Lagenaria sp., and Luffa sp.). There
was also a significant host aphid effect in T. indicus where wasps
parasitizing A. gossypii had higher parasitism rates compared to Aphis
craccivora Koch and Myzus persicae (Sulzer) (Singh and Srivastava 1990).
Fungi. The two best studied pathogens are Neozygites fresenii
(Nowakowski), and Cephalosporium (=Verticillium) lecanii (Zimm.). Several
other fungal pathogens have also been reported: Arthrobotrys sp.,
Entomophthora aphidis Hoffm., and Entomophthora delphacis Hori (Sanchez-Peña
1993, Shimazu 1977).
Neozygites fresenii (Zygomycetes: Neozygitaceae) takes 3, 4, 5-6, and 6-
8 days to develop at temperatures of 30, 25, 20, and 15°C, respectively.
Furthermore, at 35°C the fungus did not kill aphids (Steinkraus et al.
1993). Neozygites fresenii was able to produce up to 9,835 conidia from a
single aphid. The number of conidia was correlated with aphid size, but the
authors suggested that handling or storage properties of larger aphids could
explain their observation (Steinkraus et al. 1993). Temperatures above 35°C
and humidity below 85% inhibit conidial discharge from A. gossypii cadavers
(Steinkraus and Slaymaker 1994). Infection starts with primary conidia
germinating and forming capilliconidia. This process is so sensitive to
humidity that at 95% RH and 25°C, 90% of the primary conidia germinate,
while only 19% germinate at 89% RH (Steinkraus and Slaymaker 1994). This
fungus can be a major cause of aphid mortality in cotton grown in the
Texas/Arkansas area of the USA (Steinkraus et al. 1993, Steinkraus et al.
1991). The fungus has a distinct diel periodicity in spore discharge, with
greatest activity occurring between the hours of 0100-0500 hours with almost
no activity between 0900-2400 hours (Steinkraus et al. 1996). This fungus
has not been reared on artificial media, but Steinkraus et al. (1993)
reported on propagation in an aphid colony and longevity of the fungus in
cold storage. A primary route for infection of new aphid colonies may be
through infected alates (Steinkraus et al. 1995). Detection of infected
alates may also provide an early indication of impending epizootics
(Steinkraus et al. 1995).
Cephalosporium lecanii is an important source of mortality for aphids
under greenhouse conditions, but there are no reports of its impact on A.
gossypii under field conditions. The effectiveness of the fungus is
emphasized by its use as an aphicide in commercial greenhouses in the UK
(Hall 1985, Sopp et al. 1990). Its success in this capacity is partly due to
the ability of the fungus to grow in artificial media. As one might expect,
different strains of the fungus show different growth rates and different
levels of pathogenicity (Hall 1982, Kitazawa et al. 1984, Yokomi and
Gottwald 1988).
Other Biocontrol Agents. One group of organisms is conspicuously missing
from the literature on the biological control of this aphid: viral
pathogens. Another group (the mites) have just started to show up in the
literature with the study of Allothrombium pulvinum (Acari: Trombidiidae).
However, these papers deal mainly with mite distribution in the field (Zhang
et al. 1993, Zhang and Chen 1993).
Miscellaneous. Potts and Gunadi (1991) reported a decrease in A.
gossypii populations in potato that is intercropped with Allium cepa L. or
Allium sativum L. To get the reduction, the onions had to be planted within
0.75 meters of potato plants. However, intercropping poses a problem when
the minor crop harbors a disease of the primary crop. Such a system has been
documented in Taiwan where banana was interplanted with cucumber (an
alternate host for banana mosaic virus) (Tsai et al. 1986). A similar effect
also occurs when alternate hosts (of aphid and virus) are in neighboring
fields (Tsai et al. 1986).
Competition is another form of species interaction. Regupathy and
Jayaraj (1974a) reported a negative relationship between A. gossypii and
Amrasca devastans (a leafhopper) on okra with an r
2
of 0.6. The relationship
was significant only for aphid and leafhopper nymphs, not leafhopper adults.
Presumably this effect is a result of crowding and host quality reduction at
high aphid densities. The effect of host quality decline due to feeding by
A. gossypii is a problem during the commercial production of Kerria lacca
(Kerr) (Lac insects) on Flemingia macrophylla † O. KZE. ex Prain (Sen et al.
1987). Aphid feeding causes premature leaf drop, wilting, and desiccation of
the plant. The role, if any, crowding may have played in reducing Lac insect
densities was not examined.
FUTURE DIRECTIONS
There are four research areas that should be particularly fruitful.
1) The causes for alate production are still not understood. We think
that all of the significant elements have been identified, but their order
of importance and their interactions have not been examined. However, in
order to fully explore the role of nutrition, a suitable artificial diet,
one where 30 or more generations can survive, needs to be developed.
Understanding the mechanism for alate formation would be useful in
understanding the spread of this insect through the environment and may
improve understanding of the role of this aphid as a virus vector.
2) Our understanding of the ecological interactions of A. gossypii are
improving, but there are still large gaps. The possibility that a virus will
alter host physiology to promote alate formation in this aphid should
receive more attention. Research on the impact of natural enemies as it
affects the aphid's biology would also be useful. Especially important is
work which examines the interactions between different mortality factors and
the rest of the aphid's biotic and abiotic environment.
3) The relationship between soil fertility and aphid population growth
should be examined further. It is clear that effects like soil fertility,
soil salinity, and soil moisture all influence plant nutrient levels. It is
also clear that this influences aphid abundance. However, when specific
elements are examined (like amino acid composition in the phloem) there is
no clear correlation.
4) What is the biochemical mechanism for host adaptation in this aphid.
One knows that it involves a physiological change, that there is a limit to
the degree that the aphid can change during maturation, and that the parent
passes some of this change on to the nymphs. The latter effect may sound
Lamarckian; however, it may be that nymphs still inside the adult aphid are
the most physiologically flexible. Hence, parental stress will produce
changes in nymphs such that they appear to adapt to a new host with each
passing generation.
As a final note, there are three things we would change about many of
the articles used in this paper. First: although, research is easier using
leaf cages or excised leaves, these procedures modify aphid biology by
modifying the environment in which the aphid lives. Sometimes a cage is
necessary. Under such constraints, the cage should enter the analysis as a
treatment effect, and the experiment should be planned accordingly. Second:
auxiliary information such as light source, light intensity, temperature,
relative humidity, and aphid size should be included as routine
measurements. It is also important to report the conditions under which the
aphid was reared, and for how long. Finally, some record should be kept of
the field host upon which the aphid was found. Such information will greatly
facilitate comparing one set of research results with the results from other
work.
ACKNOWLEDGMENT
I would like to thank Xiong Deng for interpreting articles published in
Chinese. We would also like to thank the people in the Interlibrary Loan
department at Oklahoma State University. This paper was a part of the senior
author's doctoral dissertation, and funded by the Department of Entomology
at Oklahoma State University. This work was also supported by Hatch Project
OKLO-2040, CSRS-SRIPM grant #91-34103-5844, CSR - special grants #92-34146-
6995, and CSRS special grant # 93-34146-8408.
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TABLE 1: Plant Families With Members Serving As Hosts For Aphis gossypii. Hosts that are a source of food, fiber, or
ornamental are listed under the appropriate family according to the Cronquist system of classification as found in Jones
and Luchsinger (1986).
Family Species Common Name
Damage
a
Citation
Division: Pinophyta (Gymnosperms) Class: Coniferopsida
Order: Coniferales
Cupressaceae 35
Division: Magnoliophyta Class Magnoliopsida (Dicots)
Subclass: Magnoliidae
Order: Magnoliales
Annonaceae
Annona muricata L.
Soursop
51
13
Order: Laurales
Lauraceae Persea americana Mill. Avocado F 61
Order: Piperales
Piperaceae Piper betle L.
Piper methysticum Forest.
Betelvine
Kava
F
V
48
16
Order: Ranunculales
Ranunculaceae 44
Subclass: Hamamelidae
Order: Hamamelidales
Hamamelidaceae 35
Order: Urticales
Ulmaceae 51
Cannabinaceae 51
Moraceae 35,51
Urticaceae 51
Order: Casuarinales
Casuarinaceae 35
Subclass: Caryophyllidae
Order: Caryophyllales
Nyctaginaceae 51
Cactaceae 13
Chenopodiaceae 51
Amaranthaceae 51
Portulacaceae 35
Caryophyllaceae Dianthus caryophyllus L. Carnation V 56
Order: Polygonales
Polygonaceae 51
Subclass: Dilleniidae
Order: Plumbaginales
Plumbaginaceae 35
Order: Theales
Dipterocarpaceae 51
Theaceae 35
Clusiaceae 35
Order: Malvales
Tiliaceae 51
Sterculiaceae Theobroma cacao L. Cacoa 13
Malvaceae
Hibiscus cannabinus
H. esculentus
H. syriacus
H. rosa-sinensis
Gossypium hirsutum
G. hirsutum
G. arboreum
Kenaf
Okra
Rose of Sharon
Chinese
Hibiscus
Cotton
Cotton
N
F,V
F
V?
35,51
42,43
33,34,49
30
46
1,28
14
15
Order: Lecythiadales
Lecythidaceae 13
Order: Violales
Violaceae 51
Passifloraceae Passiflora edulis Sims. Passionfruit 13
Caricaceae Carica papaya L. Papaya, Papaw 13
Cucurbitaceae
Cucumis sativus L.
Cucurbita pepo
Cucumis melo L.
Cucumber
cv. 'Michlo
Lavan'
Zucchini
Muskmelon
F,V
V
V
V
51
11,12
5
7
7
Begoniaceae 8
Order: Capparales
Capparidaceae 51
Brassicaceae
Brassica campestris L.
Turnip, cv.
Yorii
V
51
21
Order: Ericales
Epacridaceae 13
Ericaceae 35
Order: Ebenales
Ebenaceae Diospyros virginiana L. Persimmon F 61
Subclass: Rosidae
Order: Rosales
Pittosporaceae 35
Crassulaceae 35
Saxifragaceae 35
Rosaceae
Pyracantha sp.
Malus pumila Mill.
Fragaria sp.
Pyrus communus L.
Eriobotrya japonica
Lindl.
Pyracantha
Apple
Strawberry cv.'Tufts'
pear
Loquat
F
F
N
N
35,51
45
26,27
63
19
13
Order: Fabales
Mimosaceae 35
Caesalpiniaceae 51
Fabaceae
Vigna unguiculata (L.)
Walp.
Phaseolus vulgaris L.
Glycine max (L.) Merrill
Trifolium alexandrinum
Vigna radiata (L.) R.
Wilcz.
Vigna mungo (L.)
Maughania macrophylla
Cowpea, line
TVu54
Bean cv. 'The
Prince'
Soybean
Egyptian Clover
Greengram
Blackgram
V
V
V
V
V
V
C
51
6
6
6
37
47
9
10
Order: Proteales
Proteaceae Macadamia sp. Macadamia Nut F 35,61
Order: Myrtales
Sonneratiaceae 13
Lythraceae 51
Myrtaceae
Psidium guava
Guava
N
35,51
19
Punicaceae
Punica granatum L.
Pomegranite
51
13,67
Onagraceae 35
Combretaceae 35
Order: Celastrales
Celastraceae 35
Order: Euphorbiales
Euphorbiaceae 51
Order: Rhamnales
Vitaceae
Vitis vinifera L.
grape
51
13
Order: Sapindales
Sapindaceae Litchi chinensis Litchi
(=Lychee)
13
Burseraceae 51
Anacardiaceae
Anacardium occidentale L.
Cashew nut
35
13
Rutaceae
Citrus sinensis (L.)
Osbeck
Citrus aurantifolia
(Christm.)
Swingle
"Marrs" Sweet
Orange
Mexican Lime
V
V
35,51
58
58
Order: Geraniales
Oxalidaceae 51
Balsaminaceae 51
Order: Apiales
Araliaceae 35,51
Apiaceae
Apium graveolens L.
Daucus carota L.
Celery
Carrot
51
13
13
Subclass: Asteridae
Order: Gentianales
Apocynaceae 35,51
Asclepiadaceae
Calotropis procera
V
51
38
Order: Solanales
Solanaceae
Solanum melongena
Capsicum annuum L.
Solanum tuberosum L.
Nicotiana tabacum L.
Eggplant
Chilli
Potato
Tobacco
F, V
V
F, V
V
35,51
17,54,64
24,40,65
41,57
24,25,60
Convolvulaceae
Ipomoea batatas (L.)
Poir.
Sweet potato
V
51
31
Order: Lamiales
Boraginaceae 35,51
Verbenaceae 35,51
Lamiaceae 35,51
Order: Plantaginales
Plantaginaceae Plantago ovata Forsk. Isabgol F 52
Order: Scrophulariales
Oleaceae 13
Scrophulariaceae 44
Myoporaceae
Artocarpus altilis
Artocarpus communis
Breadfruit
Breadfruit
35
13
13
Gesneriaceae 13
Acanthaceae 51
Pedaliaceae Sesamum indicum Sesame
(=gingelly)
F 39
Bignoniaceae 35,51
Order: Campanulales
Goodeniaceae 13
Order: Rubiales
Rubiaceae
Gardenia augusta (L.)
Merrill
Gardenia
F
35,51
36
Order: Dipsacales
Caprifoliaceae 35
Order: Asterales
Asteraceae
Dendrathema grandiflorum
Kitam.
Helianthus annuus L.
Zinnia elegans Jacq.
Lactuca sativa L.
Chrysanthemum
Sunflower
Zinnia
Lettuce cv.
'Iceberg'
F
V
V
N
35,51
2,3,23,66
62
53
29
Division: Magnoliophyta Class: Liliopsida (Monocots)
Subclass: Arecidae
Order: Arecales
Arecaceae Cocos nucifera L. Coconut 13
Order: Arales
Araceae
Colocasia esculenta (L.)
Schott
Taro
51
Subclass: Commelinidae
Order: Commelinales
Commelinaceae 51
Order: Cyperales
Poaceae
Saccharum officinarum L.
Zea mays L.
Triticum aestivum L.
Sugarcane
Corn
Wheat
V
V
N
32
55,13
20,13
Subclass: Zingiberidae
Order: Zingiberales
Musaceae Musa acuminata Colla.
Musa textilis Née
Banana
Abaca
V
V
59
50
Zingiberaceae 51
Cannaceae 51
Subclass: Liliidae
Order: Liliales
Liliaceae
Lilium longiflorum Thunb.
Allium sativum
Easter lily
Garlic
F
V
35
18
4
Iridiaceae 51
Dioscoreaceae Dioscorea batatas Chinese Yam V 22
Order: Orchidales
Orchidaceae 13
a
V= virus vector. F= feeding Damage. C= competition. N= present, but nature of problem not directly stated (e.g.,
where authors use phrases like "injurious", or "subject to attack").
1) Abdel-Wahab and Rizk 1970; 2) Adams and Hall 1990; 3) Adams et al. 1990; 4) Ahlawat 1974; 5) Antignus et al. 1989;
6) Atiri et al. 1986; 7) Banik and Zitter 1990; 8) Batchelder 1927; 9) Benigno 1979; 10) Bhattacharya and Srivastava 1987;
11) Binnis 1971; 12) Brouwer and Dorst 1975; 13) Carver 1996; 14) Cauquil 1981; 15) Chakravarthy and Sindu 1986; 16) Davis
et al. 1996; 17) Dhandpani and Kumaraswami 1982; 18) Doucette 1962; 19) El-Nagar et al. 1985; 20) Fagundes and Arnt 1978;
21) Fujisawa 1985; 22) Fukumoto and Tochihara 1978; 23) Furk and Vedjhi 1990; 24) Gahukar and Nariani 1982; 25) Gooding and
Kennedy 1985; 26) Hameed and Dinabandhoo 1978; 27) Hameed et al. 1975; 28) Hassanein et al. 1971; 29) Hinsch et al. 1991;
30) Inaizumi 1980; 31) Kennedy and Moyer 1982; 32) Khurana and Singh 1972; 33) Kisha 1978; 34) Kishore and Rai 1982; 35)
Leonard and Walker 1971; 36) Miller and Williams 1989; 37) Mishra et al. 1980; 38) Mohan and Sharma 1987; 39) Muralidharan
et al. 1977; 40) Nandanwar et al. 1976; 41) Nderitu and Mueke 1986; 42) Norman and Sutton 1969; 43) Norman et al. 1972; 44)
O'Brien et al. 1993; 45) Pinnock et al. 1974; 46) Pospisil 1972; 47) Ramakrishnan et al. 1973; 48) Raut and Bhattacharya
1987; 49) Regupathy and Jayaraj 1972; 50) Retuerma 1982; 51) Roy and Behura 1983; 52) Sagar and Jindla 1984; 53) Sastry et
al. 1973; 54) Seth and Raychaudhuri 1977; 55) Shaunak and Pitre 1973; 56) Singh and Singh 1989; 57) Singh et al. 1984; 58)
Smith and Farrald 1988; 59) Summanwar and Marathe 1982; 60) Suzuki and Akazawa 1978; 61) Swirski et al.1991; 62) Theuri et
al. 1987; 63) Trumble et al. 1983; 64) Vyanjane and Mali 1981; 65) Wadnerkar and Deshpande 1977; 66) Webb and Argauer 1974;
67) Zhang and Zhong 1990.
TABLE 2: Virusus Vectored By Aphis Gossypii. Virus type is based on Francki et al 1985. The question mark after the
virus type indicates a tentative placement in that group. Viruses of unknown afinity may be new viruses that have not been
placed, or may be variants of a virus already listed.
Type Virus Host Plant Country Source
unknown Afinity Calotropis Mosaic Virus Calotropis procera India 20
Carnation Mottle Virus Dianthus caryophyllus India 32
Citrus Woody Gall Virus Citrus Peru 41
Greengram Mosaic Virus Vigna mungo & other hosts India 23
Infectious Chlorosis Banana India 37
Leaf Crinkle of Sunflower Sunflower Kenya 39
Mosaic of Bean Vigna mungo Philippines 6
Mosaic of Garlic Allium sativum L. India 1
Muskmelon Yellow Stunt Virus Cucumis melo & Cucurbita pepo France? 26
Solanum torvum Mosaic Virus Solanum torvum India 33,35
Yellow Blotch of Sunflower Helianthus annuus Kenya 39
Yellow Vein Mosaic Virus Abelmoschus esculentus India 24
Alfalfa Mosaic Virus Alfalfa Mosaic Virus Trifolium alexandrinum
Eggplant
India
India
19
40
Carlavirus? Chinese Yam Necrotic Mosaic
Virus
Dioscorea batatas Japan 12
Carlavirus Lily Symptomless Virus 36
Caulimo-virus Cauliflower Mosaic Virus 36
Clostero-virus 1 Citrus Tristeza Virus Citrus USA 27,43
Cucumo-virus Cucumber Mosaic Virus Zinnia elegans
Turnip
Banana
India
Japan
India
28
11
18
Cucumber Japan
Netherlands
42
7
Capsicum spp.
Cucumis melo & Cucurbita pepo
Nicotiana tabacum & other
hosts
India
USA
India
13,31
5
29
Luteovirus Potato Leafroll Virus Potato India 34
Potyvirus Bean Common Mosaic Virus 36
Cowpea Aphid-Borne Mosaic
Virus
Vigna unguiculata Nigeria 4
Onion Yellow Dwarf Virus 36
Papaya Ringspot Virus 36
Pepper Veinal Mottle Virus Pepper (Capsicum sp.) Nigeria 3
Potato Virus Y Nicotiana tabacum
Capsicum annuum & other hosts
Potato
Japan,USA
India
India
14,38
16
34
Sri Lankan Passion Fruit
Mottle Virus
Passiflora edulis f.
flavacarpa
Sri Lanka 9
Sugarcane Mosaic Sugarcane
Corn
Musa textilis
India
USA
Philippines
17
30
25
Turnip Mosaic Virus Turnip
radish
Japan
Japan
10,11
10
Watermelon Mosaic Virus 1 Cucumber
Cucurbita maxima & other
hosts
Cucumis sativus, & other
hosts
Japan
Japan
Mexico
42
44
8
Watermelon Mosaic Virus 2 Cucurbita spp. Israel 2
Yam Mosaic Virus 36
Potyvirus ? Commelina Mosaic Virus Commelina diffusa USA 21
Sweet Potato Feathery Mottle
Virus
Ipomoea nil USA 15
Zucchini Yellow Mosaic Virus Pumpkin
Cucurbits
Japan
Israel
22
2
1) Ahlawat 1974; 2) Antignus et al. 1989; 3) Atiri & Dele, 1985; 4) Atiri et al. 1986; 5) Banik & Zitter, 1990; 6)
Benigno 1979; 7) Brouwer & Dorst 1975; 8) Camino-Lavin, et al. 1974.; 9) Dassanayake & Hicks 1992; 10) Fujisawa & Iizuka
1985; 11) Fujisawa 1985; 12) Fukumoto & Tochihara 1978; 13) Gahukar & Nariani 1982; 14) Gooding & Kennedy, 1985; 15)
Kennedy & Moyer 1982; 16) Khatri & Sekhon 1974; 17) Khurana & Singh 1972; 18) Mali & Rajegore 1979; 19) Mishra et al. 1980;
20) Mohan & Sharma 1987; 21) Morales & Zettler 1977; 22) Ohtsu et al. 1985; 23) Ramakrishnan, et al. 1973; 24) Regupathy &
Jayaraj 1972; 25) Retuerma 1982; 26) Risser et al. 1981; 27) Roistacher et al. 1984; 28) Sastry et al. 1973; 29) Seth &
Raychaudhuri 1977; 30) Shaunak & Pitre 1973; 31) Singh & Singh 1977; 32) Singh & Singh 1989; 33) Singh et al. 1975b; 34)
Singh et al. 1984; 35) Singh, et al. 1975a; 36) Smith 1972; 37) Summanwar & Marathe 1982; 38) Suzuki & Akazawa 1978; 39)
Theuri et al. 1987; 40) Vyanjane & Mali 1981; 41) Wallace & Drake 1969; 42) Yamamoto & Ishii 1983; 43) Yokomi & Damsteegt
1991; 44) Yonaha et al. 1977;
Table 3: Overwintering hosts for A. gossypii, including hybernating viviparae, viviparae, or nymphs.
Plant Family Host Plant Stage Country Citation
Brassicaceae Capsella bursa-pastoris * viviparous adult alate
viviparous adult apterous
Japan 1
Onagraceae Oenothera speciosa * unspecified USA 2
Polygonaceae Rumex spp. * unspecified USA 2
Scrophulariaceae Veronica persica*
Veronica arvensis
viviparae
viviparae
Japan
Japan
4
5
Malvaceae Hibiscus syriacus *
Althaea rosea
viviparae
viviparae
Japan
Japan
3
3
Lamiaceae Lamium amplexicaule viviparae Japan, USA 3,2
Compositae Chrysanthemum molifolium viviparae Japan 3
Roseaceae Fragaria chiloensis viviparae Japan 3
Plantaginaceae Plantago asiatica viviparae Japan 5
Boraginaceae Symphytum officinale viviparae Japan 5
* these hosts have been shown to be used all year by this aphid.
1) Inaizumi 1986; 2) O'Brien et al. 1993; 3) Inaizumi 1980; 4) Nozato 1987; 5) Inaizumi 1970;
... The leaf pieces were placed inside sterilized Petri plates. Adult aphids were collected from infected papaya plants and taken to the laboratory, and they were identified morphologically by consulting with keys of aphids (Ebert & Cartwright, 1997;Ghosh, 2008;Kim et al., 2010). Identified aphids were then transferred on the leaves with the help of a soft paintbrush (ten aphids per plate). ...
... The collected aphids from papaya leaves were identified as Aphis gossypii Glover by consulting with published keys (Ebert & Cartwright, 1997;Ghosh, 2008;Kim et al., 2010) and also confirmed by scientists (Zoological Survey of India, Kolkata). ...
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... There are 4700 species of Aphididae worldwide(Coeur d' Acier et al., 2010). Aphis glycines is among the most destructive species with a broad range of hosts that include over two dozens of plants worldwide (Ebert & Cartwright, 1997). They affect plants such as cotton (Gossypium hirsutum), groundnut (Arachis hypogaea) and watermelon (Citrullus lanatus) sesame (Sesamum indicum), okra (Abelmoschus esculentus), eggplant (Solanum melongena), and chili (Capsicum annuum) (Ebert & Cartwright, 1997). ...
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This book discusses the latest advances in cotton genetics and the biochemistry, physiology, bioinformatics, and genomics of the cotton plant. Chapters cover genomics and transcriptomics approaches to characterization and tagging of essential genes, novel transgenic tools to accelerate breeding against climate issues, abiotic and biotic stress pressures, biological control and machinery tools for cotton plant protection, cotton seed meal production, and sustainable and effective farming in the era of climate change and technological advance.
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