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Experimental & Applied Acarology,
14 (1992) 89-94
Elsevier Science Publishers B.V., Amsterdam
89
Specificity of a strain of
Neozygites
sp.
(Zygomycetes: Entomophthorales) to
Mononychellus tanajoa ( Acari:
Tetranychidae)
G.J. de Moraes a and I. Delalibera Jr. b
aCNPDA/EMBRAPA, Jaguariuna, SP, Brazil
bCPATSA/EMBRAPA, Petrolina, PE, Brazil
(Accepted 16 December 1991 )
ABSTRACT
de Moraes, G.J. and I. Delalibera, Jr., 1992. Specificity of a strain of
Neozygites
sp. (Zygomycetes:
Entomophthorales) to
Mononychellus tanajoa
(Acari: Tetranychidae).
Exp. Appl. Acarol.,
14: 89-
94.
Neozygites
sp. is commonly found infecting the cassava green mite,
Mononychellus tanajoa
(Bon-
dar), in parts of northeast Brazil. The introduction of this fungus into other regions requires the
knowledge of its specificity, especially in relation to natural enemies of different cassava pests. Labo-
ratory tests indicated the development of germination tubes of
Neozygites
in some females of
Tetran-
ychus bastosi
Tuttle et al. and T.
urticae
Koch, with subsequent formation of a reduced number of
hyphal bodies in some T.
bastosi.
No females of the phytoseiid predators
Amblyseius idaeus
(Den-
mark & Muma) and
Amblyseius limonicus
Garman & McGregor s.1. were infected by
Neozygites
sp.
INTRODUCTION
The work reported in this paper is part of an on-going project about the
biological control of the cassava green mite,
Mononychellus tanajoa
(Bon-
dar). This mite is native to South America and was first reported in Uganda
in the early 1970s, from where it spread over most cassava-growing areas of
Africa (Yaninek, 1988). The considerable damage it caused in Africa
prompted the search for effective natural enemies in its area of origin.
Field surveys conducted in northeast Brazil indicated that
Neozygites
sp.
was a common pathogen ofM.
tanajoa
in areas with average annual precipi-
tation between 700 and 1300 mm. The fungus was first found in the central
part of the state of Bahia, and then detected over a wide area covering almost
all states of the region (Delalibera et al., 1992).
Neozygites
has also been re-
ported attacking
Mononychellus
in Venezuela (Agudelo-Silva, 1986) and
Correspondence to: G.J. de Moraes, CNPDA/EMBRAPA, 13820-Jaguariuna, SP, Brazil.
0168-8162/92/$05.00 9 1992 Elsevier Science Publishers B.V. All rights reserved.
90 G.J. DE MORAES AND L DELALIBERA JR.
Colombia (Alvarez Afanador, 1990). However, it is not known whether the
same or different species of the fungus are involved, because of taxonomic
uncertainties in this group (Humber et al., 1981 ).
Unpublished evidence indicated the desirability of further exploring the
possibility of introducing a strain of
Neozygites
sp, in Africa for the control
of
M. tanajoa.
However, before the introduction is accomplished, several
studies are necessary, including the determination of the specificity of the
fungus, making sure that it does not affect beneficial organisms.
METHODS AND MATERIALS
The ability of a strain of
Neozygites
sp. to infect the phytophagous Tetra-
nychidae
Tetranychus bastosi
Tuttle et al. and T.
urticae
Koch, and the pre-
daceous Phytoseiidae
Amblyseius idaeus (Denmark
& Muma) and
A. limon-
icus
Garman & McGregor s.1. was compared in the laboratory with the ability
to infect
M. tanajoa.
Both
Tetranychus
are common species on different crops
in northeast Brazil, while both
Amblyseius
species are the most common pre-
dators of
M. tanajoa
in that region. Cassava leaves with
M. tanajoa
infected
by
Neozygites
sp. were collected from Piritiba, Bahia, put in paper bags inside
a cool-box and conducted to the laboratory. Healthy
M. tanajoa
were col-
lected from cassava leaves in Petrolina, Pernambuco.
Tetranychus bastosi
were
taken from recently infested cassava plants from a greenhouse, while T.
urti-
eae
were taken from colonies maintained for at least 2 years on bean plants in
a greenhouse in Petrolina.
Amblyseius idaeus
were collected from cassava in
Capita Grosso (test 2) and Jacobina (test 3 ), both in the state of Bahia.
Am-
blyseius limonicus
s.1. were collected on the same host in Cruz das Almas,
Bahia (tests 4 and 5 ) and Bacabal, Maranhao (test 6).
Upon arrival in the laboratory, mummified infected females of
M. tanajoa
were collected and stored in glass vials (0.5 cm diameter• 6 cm long), each
containing a clump of cotton sucked in glycerol to keep the humidity low
inside the vials. The vials were kept in a refrigerator (ca. 10~ for up to 5
months before the mites were used.
Two mummies taken from the vials were put in the center of opposing halves
of a disk of cassava leaf (2 cm diameter). The disks were put inside a plastic
tray ( 19 cm diameter)< 3 cm high) containing a piece of water-saturated foam-
mat, that was in turn put inside another tray (23 cm diameter)< 6 cm high)
containing 500 ml of a saturated K2Cr207 solution, and maintained at 24~
The top of the larger tray was closed tightly with a piece of plastic material
(Magi-pack | ). This procedure should provide an ambient RH of ca. 98%
(Winston and Bates, 1960). After 48 h, the disks were observed under a dis-
secting microscope to assure that sporulation had occurred. Each disk was
transferred to plastic rearing units (2 cm diameter X 1.6 cm high) containing
a piece of wet filter paper on the bottom. One-day-old adult females of the
SPECIFICITY OF NEOZYG1TES TO MONONYCHELLUS
91
species to be tested were subsequently put inside the rearing units containing
the mites with the sporulating fungus. Ten tetranychids or two phytoseiids of
either species were put in each rearing unit. Ten replicates were used in each
test. The rearing units were maintained at 29 _+ 4~ and 75 + 25% RH for 2
days. That temperature favored the mobility of the mites, facilitating contact
with the fungus and consequent infection. After this period, the mites were
transferred to new rearing units, containing the disks of cassava leaves but no
mummies, and maintained at 25 _+ 1 ~ and 65 _+ 10% RH. At that tempera-
ture mites could survive adequately, and the leaf disk was maintained suita-
ble for over 2 days. Repeated transferrals of the mites to new rearing units
were done every third day until the end of the observation period.
Amblyseius
idaeus
and
A. limonicus
s.1. were fed a surplus of all stages of
M. tanajoa,
whenever transferred to new units.
All mites that died during the observation period as well as the remaining
live mites at the end of the period were mounted in lactophenol/Aman blue
to evaluate the level of fungus infection.
RESULTS AND DISCUSSION
The method used in storing
Neozygites
sp. was adequate for the purpose of
this study. Ca. 75% of the mummies sporulated after being stored for 9 months
(n=20), producing an average of 639 conidia (256-991) (n= 10) per
mummy, spread in an area of ca. 0.4 cm 2 around each mummy.
The procedure employed resulted in reasonable levels of infection of M.
tanajoa
by
Neozygites
(Table 1 ). Except for test 2, mortality was always nearly
zero during the first 2 days of observation, but increased considerably after
that period. Nearly maximum mortality was achieved in test 1 at the fourth
day and, for this reason, all further tests were conducted for only 5 days.
Mono-
nychellus tanajoa
killed by
Neozygites
had its hemocoel most often filled with
hyphal bodies. The overall percentage ofM.
tanajoa
with hyphal bodies var-
ied between tests from 20.4 to 79.5%, with a general average of 56.8%. In
addition, 4.2 to 20% (general average of 14.1%) of all
M. tanajoa
of each test
had germinating capilliconidia adherent to their legs, although that did not
result in the development of hyphal bodies. Apparently, those cases corre-
sponded to unsuccessful infection, considering that healthy mites were ex-
posed to capilliconia only in the first 2 days of the observation period and
that no additional mortality related to the fungus was observed after the fifth
day (test 1 ). For some unknown reasons, the highest levels ofM.
tanajoa
with
non-germinating capilliconidia (23.6%) and without adherent capilliconidia
(40.9%) were observed in test 3.
No
T. urticae
was found to contain developing hyphal bodies
of Neozygites,
while only 15.3% of
T. bastosi
contained those structures. Only 1% of the
mites of the latter species died during the observation period, but the deaths
92
G.J. DE MORAES AND I. DELALIBERA JR.
TABLE 1
Infectivity
of a strain
ofNeozygites
sp.
to five mite
species under
laboratory conditions. The starting
number of individuals in
each test
was 100
Mononychellus tanajoa
(Bondar),
Tetranychus urticae
Koch or T.
bastosi
Tuttle et
al. and 20
Amblyseius idaeus
(Denmark & Muma) or
A: limonicus
Gar-
man & McGregor s.1,
Mite species Dead mites with hyphal bodies a Overall % % Non
infection b
infected
1 2 3 4 5 6 7 8 HB GC NGC
Test
1
M. tanajoa
0 0 14 77 77 78 78 78 79.5 19.4 0 1.1
T. urticae
0 0 0 0 0 0 0 0 0 39.0 18.4 42,6
L bastosi
0 0 0 0 0 0 1 1 15.3 62.7 1.1 20i8
Averages of tests 2 and 3
M. tanajoa
0 5.5 20,5 28.5 36.0 - - - 39.2 14.9 13.4 32.5
N. idaeus
0 0 0 0 0 - - - 0 0 0 100.0
Averages of tests 4, 5 and 6
M. tanajoa
0 0 18.3 36.7 52.0 - - - 60.9 11.9 7.5 19.7
A. limonicuss.1.
0 0 0 0 0 - - - 0 0 0.5 99.5
"Cumulative daily
percentage.
bHB =dead and live mites with hyphal bodies; GC=germinating capilliconidia; NGC= non-germi-
nating capilliconidia.
were probably due to other causes, considering the
low number ofhyphal bod-
ies
in the mites. The
number of hyphal bodies in the live
T. bastosi
was also
reduced. The
overall proportions of 72.
urticae
or T.
bastosi
containing ger-
minating capilliconidia of
Neozygites
but no hyphal bodies were 39,0 and
62.7%, respectively, while the overall proportions of
those respective species
with adherent but not germinating capilliconidia were 18,4 and 1.1%.
The
.
proportions
of those species without adherent capilliconidia were
42.6 and
20.8%, respectively. The average numbers ofcapilliconidia per
T. urticae
and
T. bastosi
were 4.6 (0-41 ) and 3.1 (0-34), respectively. These results indi-
cate that the unsuitability of T.
urticae
and expecially T.
bastosi
to
Neozygites
sp. is expressed largely after the acquisition of infective structures, and gen-
erally after the penetration of fungus in the hemocoel of the mites.
No
A. idaeus
contained adherent capilliconidia or were infected by
Neo-
zygites,
despite the normal mobility of the mites in the rearing units. A single
A. limonicus
s.1. (test 4) was found with three non-germinated capilliconidia
adherent to the legs. This corroborates the fact that not a single predator of
either species has ever been found infected by
Neozygites
sp. in periodical
samples taken over the last 2 years from areas where the fungus is commonly
found infecting
M. tanajoa.
The results of this study indicate that the unsuit-
ability of both phytoseiids as host
Neozygites
is expressed at the acquisition
phase of the infective structures.
SPECIFICITY OF NEOZYGITES TO MONONYCHELLUS
93
Neozygites
was described over 100 years ago (Witlaczil, 1885), but was
only recently revived, after
Entomophthora
was split to include
Entomo-
phthora, Triplosporium
and
Conidiobolus,
and after
Triplosporium
was syn-
onymized under
Neozygites (see
Lipa, 1971; Remaudiere and Keller, 1980).
As mentioned by Lipa ( 1971 ), there was some resistance among experimen-
tal mycologists to accept these changes, and for this reason, it is possible that
some species reported in the literature after that time under
Entomophthora
may in fact belong to
Neozygites.
Recently,
Neozygites
was put into the newly
described family Neozygitaceae (Ben Ze'ev et al., 1987).
Humber et al. ( 1981 ) mentioned previous reports of six species of ento-
mophthoralean fungi attacking mites, namely
Empusa acaricida
Petch, E.
acaridis
Perch,
Conidiobolus
sp.,
Neozygites adjarica
(Tsintsadze and Varta-
petov),
N. floridanum
(Weiser & Muma) and
N. tetranychi
(Weiser). They
also reported the collection of an unidentified species of
Neozygites
on
Te-
tranychus evansi
Baker and Pritchard in northeast Brazil. Van der Geest
( 1985 ) summarized the literature on infectious diseases of spider mites, many
of which were reported to be caused by the species of
Neozygites
mentioned
by Humber et al. ( 1981 ) and other unidentified species of the same genus.
He reported several
Tetranychus
species,
Eutetranychus banksi (McGregor)
and
Oligonychus hondoensis
Ehara infected by those fungi.
Some species of
Neozygites
are known to infect insects, expecially Homop-
tera and Thysanoptera.
Neozygitesfresenii
(Nowakowski) has been reported
on aphids and the green scale,
Coccus viridis (Green),
(Witlaczil, 1885; Car-
ner and Canerday, 1968; Keller and Wuest, 1983
), N. parvispora
MacLeod et
al. has been observed on
Thrips tabaci
Lind. (MacLeod et al., 1976; Keller
and Wuest, 1983) and
N. fumosa
(Speare), on the mealybug
Phenacoccus
manihoti
Matile-Ferrero (Le Ru et al., 1985 ). Other species of this genus are
also expected to infect those or other groups of organisms (see Keller and
Wuest, 1983).
Certainly, to satisfy the requirements for the introduction of the fungus
into Africa, further tests involving organisms found in the importing coun-
tries will have to be done. However, the results of this study indicate that the
strain
of Neozygites
tested may be rather specific, because it did not cause any
significant infection to two phytophagous mite species belonging to the same
family as
M. tanajoa,
the species from which the fungus was collected, nor to
the two most common predaceous mites on cassava plants in northeast Brazil.
ACKNOWLEDGEMENT
This work was supported by the EMBRAPA/IITA agreement for biological
control of cassava pests.
94
G.J. DE MORAES AND I. DELALIBERA JR.
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