ArticlePDF Available

Abundance and natural control of the woolly aphid Eriosoma lanigerum in an Australian apple orchard IPM program

  • Central Coast Primary Industries Centre

Abstract and Figures

Woolly aphid (Eriosoma lanigerum Hausmann) (Hemiptera: Aphididae), was monitored over three growing seasons (1995--1998) to assess its abundance and management under apple IPM programs at Bathurst on the Central Tablelands of NSW, Australia. Woolly aphid infestations were found to be extremely low in IPM programs utilising mating disruption and fenoxycarb for codling moth Cydia pomonella L. (Lepidoptera: Tortricidae) control. This was the direct result of increased numbers of natural enemies. No insecticides were applied for woolly aphid control. Under the IPM strategies tested the principal control agent was identified as European earwig (Forficula auricularia L.) (Dermaptera: Forficulidae). Earwigs in combination with Aphelinus mali (Haldeman) (Hymenoptera: Aphelinidae) reduced woolly aphid infestations below the action threshold set by commercial growers. However, A. mali together with other flying natural enemies, e.g., ladybirds, lacewings and hoverflies, did not provide commercially acceptable control of woolly aphid in the absence of earwigs. Under the conventional spray program, using the broad-spectrum insecticide azinphos-methyl for codling moth control, the level of woolly aphid infestation increased with each successive season and biological control was not established. When azinphos-methyl was withdrawn, natural enemies migrated in and provided control of woolly aphid within one season. This is the first study to show that the biological control of woolly aphid can be achieved in a commercially viable IPM program.
Content may be subject to copyright.
Abundance and natural control of the woolly aphid
Eriosoma lanigerum in an Australian apple orchard
IPM program
and Richard
NSW Agriculture, Tamworth Agricultural Institute, RMB 944 Calala Lane,
Tamworth, NSW 2340, Australia;
University of Western Sydney, Bourke Street,
Richmond, NSW 2753, Australia;
CSIRO Long Pocket Laboratories, 120 Meiers
Rd, Indooroopilly, Qld 4068, Australia
*Author for correspondence; e-mail:
Received 26 April 2004; accepted in revised form 17 May 2004
Abstract. Woolly aphid (Eriosoma lanigerum Hausmann) (Hemiptera: Aphididae), was
monitored over three growing seasons (1995–1998) to assess its abundance and man-
agement under apple IPM programs at Bathurst on the Central Tablelands of NSW,
Australia. Woolly aphid infestations were found to be extremely low in IPM programs
utilising mating disruption and fenoxycarb for codling moth Cydia pomonella L.
(Lepidoptera: Tortricidae) control. This was the direct result of increased numbers of
natural enemies. No insecticides were applied for woolly aphid control. Under the IPM
strategies tested the principal control agent was identified as European earwig (Forficula
auricularia L.) (Dermaptera: Forficulidae). Earwigs in combination with Aphelinus mali
(Haldeman) (Hymenoptera: Aphelinidae) reduced woolly aphid infestations below the
action threshold set by commercial growers. However, A. mali together with other flying
natural enemies, e.g., ladybirds, lacewings and hoverflies, did not provide commercially
acceptable control of woolly aphid in the absence of earwigs. Under the conventional
spray program, using the broad-spectrum insecticide azinphos-methyl for codling moth
control, the level of woolly aphid infestation increased with each successive season and
biological control was not established. When azinphos-methyl was withdrawn, natural
enemies migrated in and provided control of woolly aphid within one season. This is the
first study to show that the biological control of woolly aphid can be achieved in a
commercially viable IPM program.
Key words: Aphelinus mali, biological control, Eriosoma lanigerum,Forficula auricularia
Woolly aphid (Eriosoma lanigerum Hausmann) (Hemiptera: Aphididae) is an
important pest of apples causing hypertrophic gall formation on the roots and
limbs of the tree (Brown et al., 1991). The galls restrict sap flow and frequently
BioControl (2005) 50: 271–291 Springer 2005
rupture providing further feeding sites for woolly aphid and allow the invasion
of fungal diseases (Childs, 1929; Weber and Brown, 1988). Heavy infestations
can reduce tree growth and vitality, destroy buds, reduce cropping, and lower
fruit quality (Childs, 1929; Essig, 1942; Bertus, 1986; Brown and Schmitt, 1990;
Brown et al., 1995).
Under Australian conditions, woolly aphid over-winter as adult females on
both the aerial and edaphic parts of the tree. Those over-wintering below
ground continue developing and reproducing at a slow rate, while those over-
wintering aerially are for the most part dormant, especially in the cooler regions
(Thwaite and Bower, 1983). In late spring–early summer, when the soil tem-
perature is approximately 10 C, young nymphs produced by over-wintering
females move up from below ground to the aerial parts of the tree (Nicholas
et al., 2003). Early colonies develop on vulnerable, thinly barked areas, such as
around pruning cuts, or splits caused by past heavy cropping. As the season
progresses colonies develop on the new season’s growth. Once feeding has
commenced woolly aphid remains sessile unless disturbed (Asante, 1994). In
autumn nymphs migrate to the roots (Lloyd, 1961). In Australia, where there
are few alternative winter hosts, e.g., American elms (Ulmus americana L.),
woolly aphid is for all practical purposes anholocyclic, living on apple as an
asexual viviparae (Nicholls, 1919). Commercial control of woolly aphid has
relied on resistant rootstocks and chemicals since the early 1900s (Froggatt,
1903; Nicholls, 1919; Thwaite, 1997). Woolly aphid has several natural enemies
in Australia, including lacewings, ladybirds, hoverflies and earwigs, all of which
are suppressed by azinphos-methyl (Asante, 1997; Nicholas et al., 1999).
Introduced in 1923 the parasitoid Aphelinus mali (Haldeman) (Hymenoptera:
Aphelinidae) is reported to have provided a significant level of control (Wilson,
1960). The European earwig Forficula auricularia L. (Dermaptera: Forficuli-
dae), which is wide spread in Australia, is capable of consuming up to 106
aphids per day (McLeod and Chant, 1952; Asante, 1995).
Earwigs have, by association, been shown to play an important part in
controlling woolly aphid in the absence of broad-spectrum insecticides (Anon,
1969; Ravenberg, 1981; Stap et al., 1987; Mueller et al., 1988). However none
of these trials showed that natural enemies could control woolly aphid under
commercial conditions, i.e., while controlling other key pests.
Two techniques, namely mating disruption and the insect growth regulator
fenoxycarb, are now firmly established in Australian apple orchards as viable
methods of controlling codling moth (Cydia pomonella L.), which is the key
pest of apples in mainland Eastern Australia (Thwaite, 1997). These techniques
are the basis of current commercial IPM programs in Australia (Thwaite,
1997). Codling moth mating disruption is highly species specific (Rumbo et al.,
1993) with no direct effect on woolly aphid or its natural enemies. In con-
ventional pesticide programs, controlling codling moth with azinphos-methyl
requires 6–8 applications during the season (Thwaite et al., 1995) and these
sprays affect many secondary pests and their natural enemies. Adopting an
IPM strategy, thereby reducing the use of broad-spectrum insecticides, is likely
to have indirect effects the orchard’s other inhabitants, including the woolly
aphid and its natural enemies (Nicholas et al., 1999).
Woolly aphid has been studied extensively under conventional pesticide
programs, but its abundance in IPM programs was previously unknown. The
aim of this study was to assess the abundance of woolly aphid in IPM pro-
grams (i.e., in the absence of broad-spectrum insecticides) and investigate the
potential of natural enemies to suppress the pest population.
Materials and methods
The trial site
This study was conducted at Bathurst Agricultural Research Station located on
the Central Tablelands of New South Wales, Australia (Lat. 3326¢S. Long.
14934¢E). The orchard, planted in 1977, was a 1.7 ha block of apple trees
divided into six (3·2) discrete 0.3 ha blocks of 189 trees each. Each block had
nine rows of 21 trees, made up of three rows each of the cultivars Red Deli-
cious, Granny Smith and Jonathan. All trees were grafted on to Merton
Malling Series (MM) 106 (woolly aphid resistant) rootstock. Planting distances
were 5 m between rows and 3 m between trees. Blocks were 10 m and 12.5 m
apart on their long and short boundaries respectively. The trees were pruned to
the central leader system and an average height of 3 m. Groundcover was
controlled with herbicides within tree rows and mown between rows, as per
commercial practice. The trees were irrigated at the rate of 8 l/h for 4 h on
3 days/week, as required during dry periods.
Treatments 1995/1996 and 1996/1997 seasons
Two of the six blocks were treated with codling moth sex pheromone dis-
pensers (mating disruption technique (MD)), (Isomate
C, Biocontrol Ltd,
Brisbane, Qld, Australia), two with azinphos-methyl plus pheromone (AMD)
and two with fenoxycarb plus pheromone (FMD). The three treatments were
arranged so that all adjacent blocks received different treatments. Pheromone
dispensers were applied each September at the rate of 1000 ha
. The azinphos-
methyl and fenoxycarb sprays were applied at the recommended label rates for
codling moth control, i.e., azinphos-methyl (Benthion
500 g/kg) 100 g/100 l
and fenoxycarb (Insegar
250 g/kg) 20 g/100 l early season and 40 g/100 l late
season (Thwaite et al., 1995). The azinphos-methyl program commenced the
first week of November each year. In 1995/1996 this program comprised six
sprays with the last applied on February 22 1996. The 1996/1997 program
comprised seven sprays with the last applied on February 24 1997. The 1995/
1996 and 1996/1997 fenoxycarb programs each comprised seven sprays applied
between October 20 and January 31 and October 21 and February 5 respec-
Treatment 1997/1998 season
The MD and AMD treatments were discontinued and all blocks were put
under a fenoxycarb only program. This consisted of nine applications of fen-
oxycarb commencing on October 13 1997. Thus, there were four blocks under
a fenoxycarb program for the first time and two that were in their third season.
The ex-AMD blocks were used to monitor the migration and efficacy of any
natural enemies of woolly aphid in the first season of an IPM program.
Other pesticide applications
A minimal fungicide program using bupirimate, dithianon, dodine, fenarimol
and penconazole, as appropriate, to control apple scab (Venturia inequalis
(Cke.) Wint.) and powdery mildew (Podosphaera leucotricha ((Ell. & Ev.) E. S.
Salmon) was applied each season. Winter oil (Vicol
Victorian Chemical Co.)
was applied at the rate of 3%in September each year to control European red
mite (Panonychus ulmi (Koch)) and San Jose
´scale (Quadraspidiotus perniciosus
(Comstock)). All sprays were applied using a Hardi TS2082 air blast sprayer at
2300 l/ha (3.5 l/tree).
In the 1996/1997 season early colonies were observed to disappear quickly, and
prompted several colonies in each treatment to be tagged to aid further
observations. Colonies were tagged by tying a small length of fluoro-pink wool
to the colonised limb approximately 75 mm above the colony.
Woolly aphid was monitored visually. Each tree was rated on a scale where:
0¼no infestation; 1 ¼trace infestation, 2 ¼up to 10%of the tree with severe
infestation; 3 ¼11–25%of the tree with severe infestation; 4 ¼more than 25%
of the tree with severe infestation (modified from Bower, 1987). Trace infes-
tation was defined as £20 small colonies per tree and severe infestation as
laterals extensively covered with large colonies. One row of trees/cultivar/block
were assessed (21 trees ·3 treatment ·3 cultivars ·2 blocks). Assessment was
carried out every 2 weeks from the beginning of September to the end of May
each year.
Woolly aphid colonies were checked monthly throughout the 1996/1997 season
for parasitism by A. mali. Small colonies or short sections (22 mm) of woolly
aphid infested laterals were taken from each cultivar not monitored for other
purposes. The aphids were dip-washed in methylated spirit (70%ethyl alcohol,
30%methanol) to remove the wool, removed from the lateral and dried on
tissue paper. The proportion of black, mummified aphids was used as a relative
measure of parasitism.
Predators were monitored using rolled strips of corrugated cardboard
(100 mm ·400 mm) as artificial refuges (shelters). One shelter was pinned to
the trunk of each tree in a shady position. Predators occupying shelters were
counted every 2 weeks and released at the base of the tree. This method took
advantage of nocturnal species taking refuge during the day.
Predator exclusion
Non-flying predators were prevented from entering the canopy of eight trees in
each cultivar in the MD and FMD treatments (four per replicate). The trunks
were banded with a 150 mm wide strip of green plastic sheet coated on both
sides with the sticky chemical polybutene (Tree Tanglefoot Pest Barrier,
Tanglefoot Co., USA). The polybutene was cleaned and replenished as re-
quired. A minimum air gap of 150 mm was maintained to reduce the move-
ment of non-flying predators between adjacent trees.
Sticky bands have the potential to reduce the upward migration of woolly
aphid crawlers from the roots early in the season (Barnes et al., 1994). To
overcome this, an apple seedling, heavily infested with woolly aphid, was at-
tached in the canopy of each banded tree, and an adjacent unbanded tree.
Sticky bands and woolly aphid infested seedlings were applied on December 12
1996 (1996/1997 season) and October 27 1997 (1997/1998 season). Woolly
aphid infestation, excluding those on the infested seedlings, was monitored
every 2 weeks. The artificial shelters for predators were positioned above the
exclusion bands.
Data analysis
Analysis of variance (ANOVA) was used to determine significant differences
between treatments and cultivars for levels of woolly aphid infestation, and the
number of predators in artificial shelters. All differences were compared at the
5%level (p£0.05) of significance and Tukey’s multiple comparison test was
used to separate means if significant differences were found. Pearson’s prod-
uct–moment correlation coefficients were calculated to test the relationship
between the number of earwigs occupying artificial shelters and the level of
woolly aphid infestation. Non-linear regression analysis of the combined data
from trees fitted with predator exclusion bands and unbanded trees was used to
estimate the number of earwigs, as recorded in artificial shelters, required to
eliminate woolly aphid from each apple cultivar.
Woolly aphid infestation
In the 1995/1996 and 1996/1997 seasons, small isolated colonies of woolly
aphid were first observed in early October in all treatments and in all cultivars
(Figures 1 and 4). These colonies (tagged with fluoro-pink wool) were often not
present on subsequent monitoring dates. Under the AMD treatment there was
no significant difference in the level of woolly aphid infestation between the
1995/1996 and 1996/1997 seasons, however it was significantly lower during the
1997/1998 season when the AMD plots were put under a fenoxycarb only
program (Figure 2).
There was no significant difference in the level of woolly aphid infestation
when comparing blocks in their first season under a fenoxycarb only (IPM)
program with those in their third season (Figure 3).
Cultivar effects
There was no significant difference between the cultivars in the level of woolly
aphid infestation within individual treatments, although in all treatments the
trend was for Red Delicious to have slightly higher infestation than Granny
Smith and Jonathon. However, pooling the treatment data showed that Red
Delicious had significantly higher levels of infestation than in either Granny
Smith or Jonathan in both the 1995/1996 and 1996/1997 seasons (Figure 4a
and b).
Treatment effects
After pooling the cultivar data, woolly aphid infestations in the AMD blocks
were shown to increase markedly from late November in 1995 and early
December in 1996. Infestation then remained significantly higher than in the
MD and FMD treatments (Figure 1a and b). Infestation remained low in the
MD and FMD treatments throughout the season. There was no significant
difference in infestation between the MD and FMD treatments in either season
(Figure 1a and b).
Due to the low levels of woolly aphid infestation in the MD and FMD
treatments, the samples collected were small (350–2,500 aphids) compared with
those from the AMD treatment (up to 8,000 aphids). On February 23 1997 the
level of parasitism by A. mali had reached 60, 55 and <1%in the MD, FMD
and AMD treatments respectively. The last application of azinphos-methyl was
made on February 24 1997 and by May 12 1997, the last sampling date, the
Figure 1. Woolly aphid infestation under three treatments for codling moth control,
mating disruption (MD, fenoxycarb plus MD (FMD), and azinphos-methyl plus MD
(AMD). Error bars ¼LSD (p£5%).
level of parasitism had risen to 66, 78 and 24%in the MD, FMD and AMD
treatments respectively.
Ladybird, Harmonia conformis Boisduval, and hoverfly, Macrosyrphus conf-
rator (Weid.), larvae were occasionally observed feeding on woolly aphid
during the monitoring program. The only predators of woolly aphid found
occupying the artificial shelters were European earwig Forficula auricularia L
(hereafter referred to as earwigs).
Figure 2. Seasonal comparison of woolly aphid infestation in AMD blocks over three
seasons 1995–1998.
Figure 3. Comparison of woolly aphid infestation in the first and third seasons of an
IPM program during the 1997/1998 season.
Effect of predator exclusion bands
The predator exclusion bands significantly reduced the number of earwigs
entering the tree canopy during the 1996/1997 season (p£0.001, assessed every
2 weeks). Banded trees had <1 tree
on each sampling date compared with
>3 tree
(range 3–14 decreasing towards the end of the season) in the un-
banded trees. There was no significant difference between the MD and FMD
treatments in the number of earwigs in artificial shelters in trees fitted with
exclusion bands, or between these treatments in unbanded trees. Trees fitted
Figure 4. Woolly aphid infestation rating in three apple cultivars Red Delicious,
Granny Smith and Jonathan, as the mean of three treatments, MD, FMD and AMD.
Error bars ¼LSD (p£5%).
with exclusion bands were found to have significantly greater infestations of
woolly aphid than unbanded trees from December 24 1996 through until May
27 1997 when monitoring ceased. In the MD and FMD treatments there was a
high negative correlation between the mean number of earwigs/tree in the
artificial shelters and the mean woolly aphid seasonal infestation rating in all
cultivars (Delicious MD r¼)0.86 p¼0.01, FMD r¼)0.67 p¼0.02, Granny
Smith MD r¼)0.86 p¼0.005, FMD r¼)0.78 p¼0.005, Jonathan MD
r¼)0.78 p¼0.008, FMD r¼)0.82 p¼0.017). The 1996/1997 data, for each
cultivar in each treatment, was clustered into two groups, exclusion-banded
and unbanded trees (Figures 5 and 6). Data points from the exclusion-banded
trees were clustered close to the y-axis, showing high levels of woolly aphid
infestation with low numbers of earwigs in artificial shelters. Conversely, the
data points from unbanded trees were clustered close to the x-axis, showing
high numbers of earwigs in artificial shelters and low levels of woolly aphid
infestation. The exponential regression model y¼a+brx
, where
a¼minimum number of earwigs counted, b¼estimated point of zero woolly
aphid infestation, and r¼0.1 (slope), was used to fit a curve to the pooled
data, i.e., exclusion-banded and unbanded seasonal means of earwigs counted
in artificial shelters and woolly aphid infestation. This estimated the number of
earwigs required to occupy artificial shelters to prevent or eliminate woolly
aphid infestation, and was represented by the point at which the fitted curve
crossed zero. The fitted curve’s accuracy is given as the percentage of variance
accounted for by the curve and shown on each graph. For the 1996/1997
season the model estimated a required seasonal mean of 7.98 and 8.30 (Granny
Smith), and 4.98 and 5.02 (Jonathan) earwigs in the MD and FMD treatments
respectively to eliminate aerial colonies of woolly aphid. When applied to the
data from the cultivar Red Delicious the slope of the fitted curve did not pass
through zero in either treatment (Figures 5a and 6a). The same analysis was
carried out on the 1997/1998 season data, when all plots were treated with
fenoxycarb. The results showed the data to be clustered as in the 1996/1997
season, but more varied in woolly aphid infestation between trees in all culti-
vars. The fitted curve did not pass through zero for any cultivar and the
number of earwigs required to eliminate woolly aphid could not be predicted.
Predictions of woolly aphid infestation
Early season monitoring of earwigs would be a valuable tool if it could predict
the level of woolly aphid infestation later in the season, thus indicating whether
continued monitoring and control measures would become necessary. To
determine this the exponential regression model was used to fit a curve to the
number of earwigs counted in artificial shelters in both exclusion-banded and
unbanded trees in the first four sampling dates of the season (December 24,
January 8 and 22 and February 5) and the seasonal mean woolly aphid
infestation. The results showed that in the 1996/1997 season the prediction
model based on early season data supported the full season model. This
indicated that earwigs would eliminate, or reduce to extremely low levels, the
aerial colonies of woolly aphid in the cultivars Granny Smith and Jonathan
Figure 5. Relationship between European earwigs (seasonal mean) and woolly aphid
(seasonal mean) in trees fitted with predator exclusion bands and unbanded trees under
a MD treatment for codling moth control during the 1996/1997 season.
under MD and FMD treatments (Figures 7b, c, 8b and c). A higher level of
variation between trees was evident in data collected from the cultivar Red
Delicious early in the season and the model predicted that woolly aphid
Figure 6. Relationship between European earwigs (seasonal mean) and woolly aphid
(seasonal mean) in trees fitted with predator exclusion bands and unbanded trees under
a FMD treatment for codling moth control during the 1996/1997 season.
infestation in this cultivar was going to be higher than in the other two cultivars
and supported the full season prediction model (Figures 7a and 8a). Early
season predictions could not be determined for the 1997/1998 season because
the full season data was too variable.
Figure 7. Relationship between European earwigs (mean of sampling dates, 24
December, 8, 22 January and 5 February) and woolly aphid (seasonal mean) in trees
fitted with predator exclusion bands and unbanded trees under a MD treatment for
codling moth control during the 1996/1997 season.
The significantly lower levels of infestation in the MD and FMD treatments in
the 1995/1996 and 1996/1997 seasons, compared with that in the AMD treat-
Figure 8. Relationship between European earwigs (mean of sampling dates, December
24, January 8, 22 and February 5) and woolly aphid (seasonal mean) in trees fitted with
predator exclusion bands and unbanded trees under a FMD treatment for codling moth
control during the 1996/1997 season.
ment, shows that under the conditions of this trial, the abundance of woolly
aphid in IPM programs was very low. The fungicide program was applied to all
treatments and, although it is unclear whether it adversely affected beneficial
species (or woolly aphid), it did not prevent biological control of woolly aphid.
The action threshold employed by Australian apple growers to woolly
aphid is very low. They usually apply an aphicide at the first sight of infestation
or early in the season before the colonies become established, often purely as a
preventative measure. This is not because woolly aphid infestation causes
heavy crop loss but because severe infestation makes the task of picking fruit
messy and unpleasant. Contract pickers are reluctant to work in heavily in-
fested areas. Any infestation rated >1 would not be acceptable to Australian
growers. The level of infestation that occurred in the IPM treatments reported
here (where no trees were rated 2), would probably not have been detected by
most commercial growers, and therefore additional control measures would
not have been considered necessary. The woolly aphid infestation recorded in
trees treated with azinphos-methyl (many of which were rated 4), and those
fitted with predator exclusion bands (i.e., those with fewer natural enemies),
would therefore not be tolerated by commercial growers. The higher levels of
infestation in Red Delicious occurred late in the season and were present well
past the harvest period of late February to mid-March, suggesting that natural
enemies may not provide adequate control in more susceptible cultivars.
Similarly, adequate control may not be possible in growing districts where
climatic conditions are more favourable to woolly aphid development or less
favourable to natural enemies.
The significantly higher level of woolly aphid infestation in blocks treated
with azinphos-methyl, together with higher A. mali and earwig populations in
the MD and FMD treatments, supports the findings of Moreton (1969) and
Nicholas et al. (1999) that azinphos-methyl suppresses the woolly aphid’s
natural enemies and prevents effective biological control. There was no evi-
dence in this trial, nor in the reviewed literature, that azinphos-methyl stimu-
lated development or fecundity in woolly aphid.
The lack of significant differences in woolly aphid infestation between the
MD and FMD treated blocks indicate that either the full season program of
fenoxycarb did not negatively impact on the biological control of woolly aphid,
or its effects were only short lived and natural enemies moved in from adjacent
blocks. It also shows that the use of MD allows for the establishment of
biological control agents. The levels of parasitism in the MD and FMD
treatments suggest that A. mali played an important role in suppressing the
woolly aphid population, although the data should be interpreted carefully
because of the small sample size. There was no significant difference in the
percentage of parasitism per tree between these two treatments, indicating that
fenoxycarb did not suppress the A. mali population. This suggests that when
applied as a spray to the aerial parts of the tree fenoxycarb did not adversely
affect larvae developing in the mummified woolly aphid or the emerged adults.
In the AMD treatment however, parasitism remained below 1%until after the
spray program was completed, confirming that azinphos-methyl was toxic to
A. mali. The results suggest that this toxic effect lasts for up to 6 weeks fol-
lowing application. The level of parasitism in the MD and FMD treatments
had reached 60 and 55%respectively by February 1997, indicating A. mali was
playing a major role in reducing the level of woolly aphid infestation
throughout the 1996/1997 season. However, as A. mali is an alate and highly
mobile insect which would have been unaffected by the exclusion bands, it
could not have been responsible for the significant differences recorded in
woolly aphid infestation between banded and unbanded trees.
Where woolly aphid appeared early in the season, tagged colonies frequently
disappeared, indicating that predators rather than parasites were playing a sig-
nificant, if not the principal, role in controlling the population. In the exclusion
trial, significant differences were found between trees fitted with predator exclu-
sion bands and unbanded trees in both the numbers of earwigs in the artificial
shelters and the level of woolly aphid infestation. The correlation between the
level of woolly aphid and the number of earwigs in artificial shelters indicates the
earwig as the principal predator and hence control agent. Only another predator
of woolly aphid, similarly unaffected by fenoxycarb and able to access the tree
canopy principally by moving up the trunk could have produced the observed
result. No such predator was detected on the exclusion bands, in the artificial
shelters or during monitoring of the orchard fauna in earlier trials (Nicholas et al.,
1999). Adult earwigs can fly but rarely take to the wing (Phillips, 1981).
The fact that earwigs can control woolly aphid is well known in Europe (Stap et
al., 1987; Mueller et al., 1988). However these trials appear to have been conducted
in experimental orchards where the management of other pests and diseases was
not addressed. As part of the present trials, laboratory experiments confirmed that
earwigs were capable of consuming woolly aphid (unpublished data).
While earwigs were considered the key regulating agent of woolly aphid in
this study, it was not possible to investigate the control of woolly aphid in the
absence of A. mali or other flying natural enemies. The reduced insecticide
programs used in this IPM field trial would have allowed survival of other
natural enemies, including A. mali, lacewings, ladybirds and hoverflies. All
were known to occur at the trial site (Nicholas et al., 1999) and are likely to
have had a complementary effect, further reducing the level of woolly aphid
infestation in the orchard. However, the high level of woolly aphid in the trees
fitted with predator exclusion bands indicates they were not, individually or
collectively, capable of controlling woolly aphid in the absence of earwigs.
The polyphagous feeding habit of earwigs means that, although they have a
preference for live prey, particularly aphids (Asgari, 1966), their long term
survival in an orchard and hence their availability as a control agent is, unlike
A. mali, not wholly dependant on the presence of woolly aphid. This means
that earwigs can be introduced and remain established in orchards in the ab-
sence of woolly aphid. Noppert et al. (1987) used a simple deterministic sim-
ulation model to determine that eight earwigs, searching randomly, could
search the average apple tree for prey with 90%efficiency. They calculated the
earwig’s predation rate at approximately 70 aphids/earwig/night and found
that, even at the lowest predicted predation rate, earwigs could ‘eliminate’
woolly aphid. Counting earwigs in artificial shelters is a relative rather than
absolute measure of abundance, which can vary through the season depending
on factors such as the availability of alternative refuge sites and weather
(Phillips, 1981). However our finding, (based on the 1996/1997 season’s data),
that a seasonal mean of eight and five earwigs are required to eliminate woolly
aphid from the Granny Smith and Jonathan trees respectively supports the
findings of Noppert et al. (1987). The data suggest that to maintain effective
control of woolly aphid in Red Delicious more earwigs would be required than
were present in the orchard during the 1996/1997 season. Earwigs effectively
suppressed woolly aphid below the >1 rating in the cultivars Granny Smith
and Jonathan during the 1997/1998 season, although not as effectively as in the
previous season. The regression model did not predict the elimination of aerial
colonies, indicating that naturally occurring populations of earwigs may not
always provide ‘full’ control, particularly in seasons favourable to woolly aphid
development. The failure of the model to predict the number of earwigs re-
quired to eliminate woolly aphid during the 1997/1998 season is probably due
to the variability in the data. The reason for this variability is unclear but
climate may have affected woolly aphid development. Availability of alterna-
tive food and the effects of sustained fenoxycarb use can also affect earwig
development, their population and hence the predator–prey relationship
(Blaisinger et al., 1990; Sauphanor and Staubli, 1994).
The regression model predictions based on the first four sampling dates for
earwigs in the 1996/1997 and 1997/1998 seasons follow the trend of the full
season models. These similarities suggest that with further research over suc-
cessive seasons, it may be possible to develop a strategy that would enable
growers to make decisions regarding the control of woolly aphid based on the
potential of earwig populations to provide adequate biological control.
In the 1997/1998 season, when the azinphos-methyl treatment was discon-
tinued, the plots were put under a fenoxycarb program to monitor the effec-
tiveness of natural enemies in newly implemented IPM programs. The
significantly lower woolly aphid infestation under fenoxycarb, compared with
the previous two seasons under azinphos-methyl, suggests that natural enemies
migrated into the blocks rapidly. Seasonal variation in weather patterns can
account for lower levels of woolly aphid infestation in some seasons, however
this was not considered a contributing factor during this season, as a nearby
block of apples treated with azinphos-methyl recorded severe woolly aphid
infestation. Earwigs are highly mobile and known to migrate considerable
distances (up to 3 m/min) in search of food and shelter (Noppert et al., 1987).
This suggests that they have the potential to colonise orchards quickly following
the removal of broad-spectrum pesticides. The blocks used in this trial were
relatively small and further investigation is required to assess migration of
earwigs into larger orchards.
The lack of a significant difference in woolly aphid infestation between the
blocks in the first year of the fenoxycarb program and those in their third year,
together with the presence of earwigs early in the season, shows that earwigs
not only migrated into the blocks quickly, but their populations were sufficient
to provide a similar level of control. The lack of any significant difference in
woolly aphid infestation between trees fitted with artificial shelters and those
without shows that providing earwigs with artificial diurnal shelters in the tree
canopy did not improve the control of woolly aphid.
Fenoxycarb has low toxicity to earwigs and is known to reduce fertility when
applied to adults reaching or at the end of vitellogenesis (Blaisinger et al., 1990;
Sauphanor and Staubli, 1994). It also delays pre-oviposition in the offspring of
earwigs treated at the third nymphal instar (Blaisinger et al., 1990). This could
result in a reduction in the earwig population, a delay in its spring emergence or
both. However no such effects were observed over the 3 years of this study. The
lack of any significant difference between the MD and FMD blocks in the
number of earwigs present in artificial shelters indicates that either the full
season program of fenoxycarb did not suppress the earwig populations, or that
they continually migrated in from the MD treatment or surrounding vegetation.
The physiological effect of wing twisting observed in a few earwigs during this
trial is consistent with that caused by fenoxycarb in some other insects, e.g., the
German cockroach Blattella germanica L. (King and Bennett, 1989). This
observation indicates that at least some of the earwig population had been in
contact with and were adversely affected by fenoxycarb. It is thought possible
that earwig fecundity could be reduced, as reported by Blaisinger et al.(1990),
and this may adversely affect woolly aphid control in the longer term. The effect
on earwigs of other pesticides commonly used in commercial apple orchards and
the possible impact of earwigs on fruit quality requires further investigation.
The authors thank the staff at the Bathurst Agricultural Research Station and
Carol and Jason Nicholas for their assistance in the field and laboratory. This
study was funded by NSW Agriculture, the Australian Apple and Pear
Growers’ Association, Horticulture Australia Limited (previously Horticultural
Research and Development Corporation), the University of Western Sydney
and supported by Biocontrol Ltd, Brisbane and Novartis Australia.
Anon., 1969. Co-Operative Research Programme on Orchard Pest Management. Re-
search Summer 10 (unpublished report held by CSIRO Canberra).
Asgari, A., 1966. Untersuchungen u
¨ber die im Raum Stuttgart-Hohenheim als wich-
stigste Pra
¨datoren der gru
¨nen Apfelblattlaus (Aphidula pomi DeG.) auftretenden
Arthropoden. Z. fur Angew. Zool. 53: 35–93.
Asante, S.K., 1994. Seasonal occurrence, development and reproductive biology of the
different morphs of Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae) in the
Northern Tablelands of New South Wales. J. Aust. Entomolo. Soc. 33: 337–344.
Asante, S.K., 1995. Functional responses of the European earwig and two species of
Coccinellids to densities of Eriosoma lanigerum (Hausmann) (Hemiptera: Aphidi-
dae). J. Aust. Entomol. Soc. 34: 105–109.
Asante, S.K., 1997. Natural enemies of the woolly apple aphid, Eriosoma lanigerum
(Hausmann) (Hemiptera: Aphididae): a review of the world literature. Plant Pro-
tection Quart. 12: 166–172.
Barnes, B.N., M.C. Knipe and F.J. Calitz, 1994. Trunk barriers provide effective control
of banded fruit-weevil on apples and nectarines. Deciduous Fruit Grower 144: 9.
Bertus, A.L., 1986. Sooty Mould. Agfact H1.AB.5, 2nd edn. Department of Agriculture
NSW, Australia.
Blaisinger, P., B. Sauphanor, J.C. Kienlen and F. Sureau, 1990. Effet des regulateurs de
croissance de insectes sur le developpement de Forficula auricularia. [Effect of insect
growth regulators on the development of Forficula auricularia.]In: ANPP Associa-
tion Nationale pour la Protection des Plantes. Relations entre les traitements phyto-
sanitaires et la reproduction des animaux. Colloque International, 25–26 Avril 1990,
Paris, Ann. ANPP (2) pp. 75–82.
Bower, C.C., 1987. Control of San Jose
´scale (Comstockaspis perniciosus (Comstock)
(Hemiptera: Diaspididae)) and woolly aphid (Eriosoma lanigerum (Hausmann)
(Hemiptera: Pemphigidae)) in an integrated mite control program. Plant Protection
Quart. 22: 55–58.
Brown, M.W. and J.J. Schmitt, 1990. Growth reduction in non-bearing apple trees by
woolly apple aphids (Homoptera: Aphididae) on roots. J. Econom. Entomol. 83:
Brown, M.W., D.M. Glenn and M.E. Wisniewski, 1991. Functional and anatomical
disruption of apple roots by the woolly apple aphid (Homoptera: Aphididae). J.
Econom. Entomol. 84: 1823–1826.
Brown, M.W., J.J. Schmitt, S. Ranger and H.W. Hogmire, 1995. Yield reduction in
apple by edaphic woolly apple aphid (Homoptera: Aphididae) populations. J.
Econom. Entomol. 88: 127–133.
Childs, L., 1929. The relation of woolly apple aphis to perennial canker infection with
other notes on disease. Agric. Exp. Station Bull. 324: 3–31.
Essig, E.O., 1942. Woolly apple aphid infesting apple cores. J. Econom. Entomol. 35:
Froggatt, W.W., 1903. Woolly aphis, or American blight (Schizoneura lanigera, Haus-
mann). Agric. Gazette NSW 14: 18–25.
King, J.E. and G.W. Bennett, 1989. Comparative activity of fenoxycarb and hydroprene
in sterilizing the German cockroach (Dictyoptera: Blattellidae). J. Econom. Entomol.
82: 833–838.
Lloyd, N.C., 1961. The woolly apple aphid. The Agric. Gazette 72(1): 652–654, 659.
McLeod, J.H. and D.A. Chant, 1952. Notes on the parasitism and food habits of the
European earwig, Forficula auricularia L. (Dermaptera: Forficulidae). Can. Entomol.
84: 343–345.
Moreton, B.D., 1969. Beneficial Insects and Mites. Bulletin 20. Her Majesty’s Stationery
Office, London.
Mueller, T.F., L.H.M. Blommers and P.J.M. Mols, 1988. Earwig (Forficula auricularia)
predation on the woolly apple aphid, Eriosoma lanigerum.Entomol. Exp. Appl. 47:
Nicholas, A.H., W.G. Thwaite and R. Spooner-Hart, 1999. Arthropod abundance in an
Australian apple orchard under mating disruption and supplementary insecticide
treatments for codling moth, (Cydia pomonella L. (Lepidoptera: Tortricidae). Aust.
J. Entomol. 38: 23–29.
Nicholas, A.H., W.G. Thwaite and R. Spooner-Hart, 2003. Control of woolly aphid,
Eriosoma lanigerum (Hausmann) (Hemiptera: Pemphigidae) on mature apple trees
using insecticide soil-root drenches. Aust. J. Entomol. 42: 6–11.
Nicholls, H.M., 1919. The Woolly Aphis (Eriosoma lanigerum). Bulletin No. 83. Agri-
cultural and Stock Department, Tasmania.
Noppert, F., J.D. Smits and P.J.M. Mols, 1987. A laboratory evaluation of the Euro-
pean earwig (Forficula auricularia L.) as a predator of the woolly apple aphid
(Eriosoma lanigerum Hausm.). Mededel. Facul. Landbouwwetensch. Rijksuniversit.
Gent 52: 413–422.
Phillips, M.L., 1981. The Ecology of the Common Earwig Forficula auricularia in Apple
Orchards. Ph.D. Thesis. University of Bristol, UK.
Ravensberg, W.J., 1981. The natural enemies of the woolly apple aphid, Eriosoma
lanigerum (Hausm.) (Homoptera: Aphididae), and susceptibility to diflubenzuron.
Mededel. Facul. Landbouwwetensch. Rijksuniversit. Gent 46: 437–441.
Rumbo, E.R., S.M. Deacon and L.P. Regan, 1993. Spatial discrimination between
sources of pheromone and an inhibitor by the light-brown apple moth Epiphyas
postvittana (Walker) (Lepidoptera: Tortricidae). J. Chem. Ecol. 19: 953–962.
Sauphanor, B. and A. Staubli, 1994. Evaluation au champ des effets secondaires des
pesticides sur Forficula auricularia et Anthocoris nemoralis: validation des resultats de
laboratoire. (Field evaluation of secondary effects of pesticides on Forficula auricu-
laria and Anthocoris memoralis: validation of laboratory results). Bull.OILB/SROP
17: 83–88.
Stap, J.S., T.F. Mueller, B. Drukker, J. Van Der Bloom, P.J.M. Mols and L.H.M.
Blommers, 1987. Field studies on the European earwig (Forficula auricularia L.) as a
predator of the woolly apple aphid (Eriosoma lanigerum Hausm.). Mededel. Facult.
Landbouwwetensch. Rijksuniversit. Gent 52: 423–431.
Thwaite, W.G., 1997. Australia’s Progress in Apple IPM, A review of integrated pest
management in Australian apple orchards. Technical Bulletin 48. NSW Agriculture,
Orange Australia.
Thwaite, W.G. and C.C. Bower, 1983. Woolly Aphid. Agfact H4. AE.3. NSW Agri-
culture, Orange, Australia.
Thwaite, W.G., R. Gordon, L.J. Penrose and R.K. Withey, 1995. Orchard Plant Pro-
tection Guide for Inland New South Wales. NSW Agriculture, Orange, NSW, Aus-
Weber, D.C. and M.W. Brown, 1988. Impact of woolly aphid (Homoptera: Aphididae)
on the growth of potted apple trees. J. Econom. Entomol. 81: 1170–1177.
Wilson, F., 1960. A review of the biological control of insects and weeds in Australia
and Australian New Guinea. Technical Communication No. 1. Commonwealth
Institute Biological Control, Ottawa, Canada.
... In addition to natural shelters formed from a variety of plant species, artificial shelters can be constructed and used as a valuable tool for supporting biological control strategies (Iuliano and Gratton, 2020). During the last twenty years, artificial shelters have been used in open agricultural landscapes for monitoring natural enemy population densities or as overwintering refuges (Horton 2004, Nicholas et al., 2005Horton et al., 2006;Kawashima and Jung, 2010). However, to the best of our knowledge, they have never been used in greenhouse crops, where they have the potential to be particularly useful for supporting the establishment and reproduction of natural enemies in cost-intensive crops. ...
... In addition, artificial shelters could facilitate monitoring or scouting tasks in greenhouse compartments. Nicholas et al., (2005) studied the phenology of predatory earwigs using cardboard bands in an apple orchard. Furthermore, Horton (2004) and Horton et al., (2006) were able to characterize the diapause and emergence phenology of diverse predator species using cardboard bands as an overwintering habitat. ...
The success of biological control programmes often depends on establishment of natural enemies in or around the crop. An emerging strategy that aims to improve establishment is through the provision of niches that act as shelters. These shelters can enhance the natural enemies’ effectiveness by providing: a suitable microclimate; protection against other predators or pesticides; and/or alternative food. Generally, shelters are natural habitats such as flower strips, intercropped areas, hedgerows, or banker plants. The use of artificial devices as shelters remains underexplored. In this study we assessed the functionality of an artificial shelter for the aphidophagous predator, Scymnus interruptus Goeze (Coleoptera: Coccinellidae). A tailor-made artificial shelter for oviposition was developed and tested in both laboratory and greenhouse conditions. Our results showed that S. interruptus females strongly preferred to use the shelters as an oviposition site compared with sweet pepper (Capsicum annuum L.) leaf discs supporting the aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), its primary prey. Furthermore, S. interruptus oviposition rate was doubled when shelters were supplied. In a greenhouse experiment, population densities of S. interruptus larvae increased twofold when shelters were provided, although this did not result in better control of aphids. Additionally, providing artificial shelters in a sweet pepper crop has potential to enhance aphid control and could also be a valuable method for monitoring predator densities in the crop.
... Early colonies form in sparsely barked places, such as pruning cuts or splits created by excessive cropping in the past. Colonies form as the season proceeds, based on the expansion of the previous season (Nicholas et al., 2005). ...
... They are extremely tough to handle due to both of their characteristics, woolly protective coat and concealed living forms. In many cases, WAA infestations may be managed using pesticide treatments Nicholas et al., 2005). However, as people become more aware of the negative effects of insecticides on human and environmental health, more emphasis is being placed on the employment of biological control agents like predators and parasitoids (Suckling et al., 1999). ...
Full-text available
Eriosoma lanigerum (Hausmann), the woolly apple aphid (WAA), is a major worldwide pest that feeds on Malus species. It is one of the most important invasive apple pests in the world, having spread from eastern North America to almost every apple-growing region on the planet. The crown and root systems of apple trees are infested by this aphid species. This aphid’s crawlers migrate up and down an apple tree continually, and the root colonies serve as a persistent source of infestation on aerial portions The WAA’s salivary gland secretions drive the injured tissues to create abnormal growths or galls that obstruct the transport of water and nutrients within the plant, weakening the tree. On the above-ground portions and on the roots of apple trees, the aphid develops tightly packed colonies coated with white, waxy, filamentous secretions. The use of resistant rootstocks, chemical, and biological control, or a combination of all three, are the mainstays of WAA management. Aphid resistance has emerged as a result of decades of pesticide usage, necessitating research to find alternatives to chemicals for pest control. This study has merely highlighted the information on the biology of the woolly apple aphid, the sorts of damage it produces, and management approaches for reducing it.
... Woolly apple aphid, Eriosoma lanigerum Hausmann The aphid is native to North America. It is a key pest of apple and is well spread in almost all apple growing areas of the world (Nicholas et al., 2005). The aphid inhabits both the aboveground (trunks arid branches) and underground parts (roots) of an apple tree. ...
... Native to North America, it is a major pest of apple worldwide (Nicholas et al., 2005). ...
... Besides, a list of predators that feed on woolly apple aphids, such as syrphids, coccinellids, chrysopids, carabids, spiders and earwigs [2,[10][11][12][13][14][15], one of the most important natural enemies of E. lanigerum worldwide is the parasitoid Aphelinus mali (Haldeman 1851) (Hymenoptera: Aphelinidae) [16][17][18]. This host-specific (solitary) endoparasitoid parasitizes all parthenogenetic stages of woolly apple aphids with a preference for third stage nymphs and older hosts, but has the disadvantage of having fewer generations per year (4-7 generations per year) compared to its host (10-12 generations per year) [3,19]. ...
... Hence, this is when the first rounds of parasitization have been successfully completed and the continuation and buildup of the parasitic wasps is guaranteed. Sprayings outside these sensitive time periods are still possible, as also confirmed by our earlier work in the development and testing of IPM complementary control strategies against E. lanigerum, which is also in line with studies of other authors [3,5,12,33]. As modern selective chemical or biological insecticides are usually most effective when sprayed against the (unprotected naked) crawlers when they are migrating to settle new colonies [33,[38][39][40], the rather accurate prediction of the start of this migration activity is an interesting feature of our E. lanigerum model. ...
Full-text available
The woolly apple aphid Eriosoma lanigerum (Homoptera: Aphidiae) is an important pest in apple orchards worldwide. Since the withdrawal or restricted use of certain broad-spectrum insecticides, E. lanigerum has become one of the most severe pests in apple growing areas across Western Europe. At present, effective limitation of woolly aphid populations relies on a good synergy between chemical control treatments and biological suppression by beneficial arthropods, especially by its main specific natural enemy, the parasitoid Aphelinus mali (Hymenoptera: Aphelinidae). To develop a knowledge-based decision support system, detailed monitoring data of both species were collected in the field (region of Sint-Truiden, Belgium) for a period of ten years (2010–2020). Aphelinus mali flights were monitored in the field, starting before flowering until the end of the second-generation flight at minimum. The seasonal occurrence of the most important management stages of E. lanigerum, e.g., start of wool production or activity on aerial parts in spring and migration of crawlers from colonies towards flower clusters or shoots, were thoroughly monitored. All obtained data were compared with historical and literature data and analysed in a population dynamics phenological model. Our outcomes showed that the emergence of first-generation A. mali adults (critical for the first parasitation activity and the basis for following A. mali generations in the continuation of the season) can be accurately predicted by the developed model. Hence, this information can be utilized to avoid insecticide sprayings with detrimental side effects at this particular moment as demonstrated by the outcomes of a field trial. In addition, the start of migration of E. lanigerum crawlers towards flower clusters or shoots is accurately predicted by the model. In conclusion, our results demonstrate that the model can be used as decision support system for the optimal timing of control treatments in order to achieve effective control of E. lanigerum with maximal biological suppression by its main natural enemy.
... Full block enclosures include the soil and ground cover below the trees and between rows, providing the habitat to support ground-dwelling predators, such as earwigs . The European earwig is a significant natural enemy of woolly apple aphid even at low densities (Mueller et al. 1988, Nicholas et al. 2005, Orpet et al. 2019. Earwig densities were not considerably different among the treatments for either year of the trial. ...
Management of direct apple pests, such as codling moth, continues to be problematic despite the widespread implementation of behavioral and chemical controls. Apple growers have increased their use of netting to protect fruit from environmental injury, with some structures enclosing the entire orchard. These enclosures represent a new pest management tactic through physical exclusion. We conducted a two-year trial to examine the effects of full exclusion netting on pests and natural enemies of apples. Insect densities and damage in trees under fully enclosed (net) cages were compared with conventionally (insecticide only) treated and untreated plots. Caged plots had 18.1- and 11.4-fold less codling moth damage than the check, and 4.9- and 4.2-fold less damage than the insecticide-only plots in 2016 and 2017, respectively. However, densities of woolly apple aphid and its parasitoid Aphelinus mali (Haldeman) (Hymenoptera: Aphelinidae) were significantly greater in the caged plots. Densities of earwigs, a typically flightless generalist predator, were not different among treatments, while adults of more mobile flying generalist predators, lacewings and syrphids, were significantly lower in cages compared with uncaged plots. These results demonstrate that although biological control may be partially disrupted, net enclosures have significant potential as a holistic apple management technique.
... In contrast, earwig abundance was affected neither by plant species richness or landscape composition nor by organic vs. conventional management in apple orchards [67]. However, pesticide reduction in apple orchards enhanced earwigs and other natural enemies and, thus, the control of woolly aphids [77]. In accordance with their reliance on ground vegetation during their early life stages, earwigs were more abundant in Spanish vineyards with spontaneous vegetation compared to bare soil and sown flower-rich cover-crops [24]. ...
Full-text available
Habitat simplification and intensive use of pesticides are main drivers of global arthropod declines and are, thus, decreasing natural pest control. Organic farming, complex landscapes, and local vineyard management practices such as implementation of flower-rich cover-crop mixtures may be a promising approach to enhance predator abundance and, therefore, natural pest control. We examined the effect of organic versus integrated management, cover-crop diversity in the vineyard inter-rows, and landscape composition on the natural pest control of Lobesia botrana eggs and pupae. Predation of L. botrana pupae was reduced by organic farming and species-poor cover-crops by about 10%. Predation rates of L. botrana eggs did not differ significantly in any of the studied management options. Dominant predators were earwigs (Forficulidae), bush crickets (Tettigoniidae), and ants (Formicidae). Negative effects of organic viticulture are most likely related to the negative nontarget effects on arthropods related to the frequent sulfur and copper applications in combination with the avoidance of strongly damaging insecticides by integrated winegrowers. While a 10% difference in predation rates on a single pest stage is unlikely to have strong practical implications, our results show that the assumed effectiveness of environmentally friendly agriculture needs to be evaluated for specific crops and regions.
... The share of F. auricularia nymphs in this orchard was 30% and 20% in 2006 and 2007, respectively, demonstrating that the prey supply was high enough for the development of earwigs in the canopies of the pear trees. Forficula auricularia is an important predator of phytophagous species in orchards (Glen, 1977;Nicholas et al., 2005;Sauphanor et al., 1994). However, this species is highly sensitive to synthetic pesticides (Cisneros et al., 2002;Fountain & Harris, 2015;Peusens & Gobin, 2008). ...
2021): The effects of various pest control regimes on the community structure and population dynamics of selected natural enemies of Cacopsyllapyri in pear orchards, Biocontrol Science and Technology To link to this article: https://doi. ABSTRACT The effects of three different pest control regimes in three pear orchards (two with integrated pest management regimes and one with an organic farming regime) on communities of arthropods were studied in a two-year experiment. Insects were collected in three stages by beating the lower branches of trees. The number of species and other taxa of natural enemies increased with the reduction in insecticide applications. A total of 2,492 individuals of 145 species and other taxa were found in the samples from the three pear orchards with different pest management practices. The most numerous groups were Araneae, with 44 species, and Coleoptera, with 42 species, followed by Hymenoptera, with 33 taxa, and Heteroptera, with 24 species. Of the total number of taxa, the share of entomophagous arthropods was, on average, 62.6%. The share of predaceous individuals was, on average, 63.7% of the total number of individuals. The number of dominant predaceous species decreased with an increase in the diversity of species and other taxa. A significant relationship was found between the number of C. pyri adults and the Shannon-Wiener index of diversity for the predaceous taxa. It was demonstrated that generalist predators and their diversity have an important influence on the regulation of pear psylla in the vegetative period. ARTICLE HISTORY
This datasheet on Forficula auricularia covers Identity, Overview, Distribution, Dispersal, Hosts/Species Affected, Diagnosis, Biology & Ecology, Environmental Requirements, Natural Enemies, Impacts, Uses, Prevention/Control, Further Information.
Earwigs have been observed as an irregular pest of increasing concern to farmers growing canola and other winter grain crops in Australia over the past decade. In this study, we tested how abiotic and biotic factors influence the feeding behaviour of earwigs. Studies were conducted with two Australian native species, Labidura truncata and Nala lividipes, and the introduced European earwig, Forficula auricularia. We constructed field-based exclusion plots that prevented F. auricularia from moving in or out of a small area of canola. We monitored F. auricularia activity and the feeding damage to canola plants throughout the winter growing season. In the laboratory, we established microcosms containing crop seedlings, as well as aphids as an alternate food source, to examine the feeding behaviour of all three species. The native earwigs L. truncata and N. lividipes did not cause feeding damage to canola or wheat but were found to actively consume aphids when present. We conclude that these species are unlikely to cause significant (economic levels) of pest damage in a field environment. In the microcosm trial, F. auricularia caused considerable damage to canola seedlings and readily consumed aphids. Forficula auricularia also caused feeding damage to canola seedlings early in the winter growing season in the field trial. However, by the end of the season, F. auricularia presence was associated with increased canola biomass. Furthermore, F. auricularia did not damage canola until all nearby aphids were consumed. Together, our field and laboratory studies suggest F. auricularia can be an important predator of aphid pests in canola, indicating a dual role of this species as both a pest and a beneficial species in winter grain systems.
Exclusion cages can quantitatively demonstrate the value of natural enemies and the biological control services they provide. Currently, in Washington State, enclosing orchards in netting is being evaluated as a pest control method, but these enclosures may also serve as an exclusion cage to natural enemies, thereby disrupting biological control. To test the effects of net enclosures on apple arthropod communities, we conducted a two-year study comparing apple herbivore, predator, and parasitoid densities in caged and uncaged plots (both receiving insecticides) to an untreated check. Effects on the various groups were influenced by size and motility. Densities of larger motile arthropods, including codling moth (Cydia pomonella (L.)), chrysopids, and syrphids, were lower in the caged plots, demonstrating exclusion. Woolly apple aphid (Eriosoma lanigerum (Hausmann)) and its parasitoid Aphelinus mali (Haldeman) densities in the caged plots were over 100-fold greater and 5-fold greater, respectively, than the other treatments. European earwig (Forficula auricularia (L.)), a generalist predator, was more abundant in the caged plots in 2016 but not in 2017. Spider mites were more abundant in the cage treatments for both years, while predatory mites had higher densities in the cages in 2017 only. These outcomes show that net enclosures change the composition of apple arthropod communities through exclusion of certain herbivores and natural enemies. In the case of some pest herbivores (e.g., codling moth), this exclusion is beneficial, but in the case of predators, it is detrimental. This study further demonstrated that exclusion of only part of the natural enemy complex may be sufficient to cause herbivore outbreaks.
Full-text available
The impact of woolly apple aphids (WAA), Eriosoma lanigerum (Hausmann), on growth and nutrient content of plant tissues was investigated with young apple trees grown in growth chambers. One hundred forty-four individually potted and caged tissue cultured 'M.7' apple trees were divided equally into two treatments (infested with five first-instr WAA on the shoot or infested with five first-instar WAA on the roots) and an uninfested control. Root galls and stem splits began forming as a result of WAA feeding after only 4 and 8 wk, respectively. Four weeks after infestation, trees in the WAA-infested treatments had significantly greater shoot and root dry weight than the control trees. After 16 wk, the growth rate of infested trees had decreased and the dry weights of roots, shoots, and leaves were greater in control trees than in treated trees. The difference in dry weight increased at 21 wk. In general, roots were more severely affected by WAA; populations of WAA on roots caused a greater reduction in tissue weights than WAA feeding on the shoot. WAA feeding also caused a decrease in foliar nitrogen and phosphorus; results from the other elemental analyses were variable. Results from the elemental analysis of root tissue indicated that WAA disrupted the nutrient balance of these apple trees.
Full-text available
Root galls on apple trees (M. 7A rootstock) created by woolly apple aphid, Erlosoma lanigerum (Hausmann), feeding were collected in the field. Root galls, ungalled roots, and ungalled sections of galled roots were analyzed for water conductivity and nitrogen concentration. Water conductivity was significantly reduced through root gall tissue. Root galls had a significantly higher concentration of nitrogen than ungalled roots. Roots of apple trees in the green house were treated with the plant hormones indole-3-acetic acid and 6-benzyl-aminopurine to induce gall formation. Woolly apple aphid galls were characterized by a proliferation of anomalous nonfunctional xylem. Growth anomalies On roots treated with 6-benzyl-aminopurine had typical xylem with a proliferation of phloem tissue. Very little internal or external deformation of roots was observed after treatment with indole-3-acetic acid. Disruption of root xylem, resulting in resistance to water conduction, is one mechanism by which woolly apple aphids reduce the growth of apple trees.
Inhibition of the behavioral responses of maleEpiphyas postvittana moths by theZ isorner of the major component of the sex pheromone,E11-14: OAc, was studied in a wind tunnel. Inhibition was detectable at a Z isomer concentration of 10% that of the major component and was greatest when it was added to the same source as the pheromone. Inhibition declined rapidly as the inhibitor was moved across-wind away from the pheromone source but was largely maintained when the sources were separated upwind or downwind. The results showed that the insects possess a high degree of temporal resolution for odor plumes of different composition.
In 1936, 1937, and 1938 several colonies of Bigonicheta setipennis (Fall.), a dipterous parasite, were liberated in Vancouver, British Columbia, to aid in the control of the European earwig, Forficula auricularia L. During September and October, 1950, an investigation was initiated to determine the abundance and distribution of this parasite and, if possible, to obtain colonies for release in Newfoundland. Approximately 6,000 of B. setipennis were reared from 50,000 trapped earwigs.
An apple orchard, planted in 1986, was studied to evaluate the effect of rootfeeding (edaphic) woolly apple aphids, Eriosoma lanigerum (Hausmann), on tree growth and productivity. Tree trunk diameter and branch linear growth were measured yearly from 1989 to 1992; fruit weight, number of fruit, fruit drop, and fruit set for 1991 and 1992 were regressed against the number of aphid colonies on roots and a root infestation rating. Linear growth was significantly reduced by edaphic woolly apple aphids in 1989 and 1991. In 1991, with low fruit production, yield was unaffected by edaphic woolly apple aphids. In 1992, with high fruit production, there was a significant reduction in the number of fruit and weight of fruit per tree by the number of root colonies, partly because of increased fruit drop and reduced fruit set. Average yield loss was 2.4 kg (5.28 pounds) or 13 apples per tree. Based on a typical packout and actual prices for 1992, the gross loss was $465.18/ha ($188.25/acre). Woolly apple aphids were on only 11.5% of terminals and wounds in this orchard. Reduction in amount of storage carbohydrates in galled roots is a partial explanation of how this aphid reduces tree growth and production.
The effect of root-feeding populations of woolly apple aphids, Eriosoma lanigerum (Hausmann), on newly planted, nonbearing apple trees in an orchard environment was studied. Roots of two-thirds of the 351 'Red Delicious' study trees were artificially infested with woolly apple aphids from a laboratory colony in 1986, 1 mo after planting. The artificial infestation resulted in 95% of the trees being infested (including controls), but did not produce more severe root infestations per tree than expected in natural infestations. The root infestation rating (mean = 0.35 on a scale of 0-1, SEM = 0.18) determined from destructive sampling of one-third of the orchard after three growing seasons was not correlated with population density above ground throughout the 3 yr of the study. Root feeding marginally reduced branch growth in the first and third year after infestation, crown length in the third year, and trunk diameter in the first and second years. Crown length was significantly reduced after 1 yr and trunk diameter was significantly reduced after 3 yr because of woolly apple aphid feeding on roots. Scion biomass also was significantly reduced by woolly apple aphid root feeding after 3 yr. We conclude that woolly apple aphid populations on roots have a slight, but significant, negative effect on growth of young non bearing apple trees in the orchard environment. We also conclude that, because of the lack of correlation between woolly apple aphid populations aboveground and on roots, sampling branch terminals and pruning scars yields no information on the density of woolly apple aphids on roots.