17 Interactions between the predatory mites Amblyseius cucumeris Oudermans and minute pirate bug Orius sauteri Poppius in prey patches of thrips Thrip palmi Karny Tương tác sinh học gi
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Interactions between the predatory mites Amblyseius cucumeris (Oudermans) and minute pirate bug Orius sauteri (Poppius) in prey patches of thrips Thrip palmi
(Karny)
Tương tác sinh học giữa nhện bắt mồi Amblyseius cucumeris (Oudermans) và bọ xít
bắt mồi Orius sauteri (Poppius) trong môi trườngcó vật mồi bọ trĩ Thrip palmi (Karny)
Vu Quoc Ngu 1 , Arnold Van Huis 1 and Nguyen Van Dinh 2
1
Laboratory of Entomology- Wageningen University- The Netherlands
2
Laboratory of Entomology- Hanoi Agricultural University
TÓM TẮT Trong điều kiện phòng thí nghiệm (độ ẩm 50 - 70%, nhiệt độ 25 ± 2 o C, 16 h ánh sáng) nghiên cứu theo dõi tương tác sinh học giữa nhện bắt mồi Amblyseius cucumeris (Oudermans) và bọ xít bắt mồi
Orius sauteri (Poppius) trong môi trường có nhiều vật mồi bọ trĩ Thrips palmi (Karny) Trong hộp
olfactometer, nhện bắt mồi không thể hiện sự ưa thích nửa hộp nào giữa 2 nửa hộp, một nửa có lá đậu với bọ trĩ còn nửa hộp kia có lá đậu với bọ trĩ và cả bọ xít bắt mồi Bọ xít bắt mồi cũng có phản ứng tương tự Khi hai động vật bắt mồi được đưa vào cùng một hộp petri, chúng không tấn công lẫn nhau, kể cả trong trường hợp không có vật chủ bọ trĩ Từ những kết quả trên có thể đưa ra kết luận rằng sẽ không có ảnh hưởng xấu lẫn nhau khi hai động vật được thả cùng trong một khoảng không gian nhằm kiểm soát vật hại rau T palmi
Từ khoá: Amblyseius cucumeris, olfactometer, Orius sauteri, Thrips palmi, tương tác sinh học
SUMMARY
In the laboratory, under conditions of 25 ± 2 o , 50 - 70% RH and 16 h light, the research
investigated biointeraction between predatory mite Amblyseius cucumeris (Oudermans) and minute pirat bug Orius sauteri (Poppius) in their prey patches of thrips Thrips palmi (Karny) In the glass petri dishes-olfactometer, A cucumeris did not show preference between the olfactometer side of bean leaf with thrips and another olfactometer side of bean leaf with thrips and heteroconspecific predator O sauteri The other predator O sauteri also showed the same strength When put them together in a bean leaf, O sauteri and A cucumeris did not attack each another even in the absence of their shared
prey From these results the conclusion can be made that there is no negative effect when both
predator A cucumeris and O sauteri are released in same field to control pests like the phytophagus thrips T palmi
Key words: Amblyseius cucumeris, biointeraction, olfactometer, Orius sauteri, Thrips palmi
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1 INTRODUCTION
Thrips, together with phytophagous mites and
aphids are the most dangerous pests of many
vegetables and ornamental crops in Vietnam
(Dinh, 2002)
Thrips palmi (Karny) is native to the tropics
and was first found on the islands of Indonesia It
is now established throughout the tropics and
subtropical zones It cannot overwinter in
temperate zones, but may manage to complete
two to three life cycles if introduced
Thrips palmi is a polyphagous species, but is
best known as a pest of Cucurbitaceae and
Solanaceae plants Among vegetables injured are
bean, cabbage, cantaloupe, chili, Chinese
cabbage, cowpea, cucumber, bean, eggplant,
lettuce, melon, okra, onion, pea, pepper, potato,
pumpkin, squash, and watermelon
In Vietnam, it was suggested that T palmi
attacked 12 species of commercial crops (Loi,
2001, cited by Yorn and Hung, 2005) Groundnut
and cucumber were considerably damaged
compared to others Potato is also a primary host
of T palmi, as it occurs from early spring to the
end of summer; in the field it can be highly
infested at the end of spring (Hung, 2002) Vuong
(1998, cited by Yorn and Hung, 2005) studied the
composition of thrips species on groundnut and
she found four species: Scirthothrips dorsalis
Hood, Frankliniella schutzei (Trybom), T palmi
and Megalurothrips usitatus Bagnall) An (1999,
cited by Yorn and Hung, 2005) reported that T
palmi was a serious pest on watermelon in Camau
province
Other studies indicated that T palmi is a
serious harmful insect on bean, eggplant and
cucumber; damage sometimes being recorded up
to 60% (Yorn and Hung, 2005)
This study was focused on interactions
between the predatory mite Amblyseius cucumeris,
the minute pirate bug Orius sauteri (Poppius) and
their shared prey the thrips species Thrips palmi
(Karny)
Both A cucumeris and O sauteri are
predators of the thrips T palmi Both species are
reared and innundatively released in fields to
protect vegetables from harmful thrips
Researchers from the Entomology laboratory
(Hanoi University) did a lot of work to produce
and release both predators to control phytophagus
mites and thrips in vegetable crops There is a
question whether one natural enemy affects the
performance of the other The interactions between two predators were also investigated under laboratorial conditions
It was tested the hypothesis that A cucumeris and O sauteri discriminate between patches with
prey only and patches with prey and the other
predator Response of A cucumeris and O sauteri
are studied in the laboratory, using petridishes Furthermore it was investigated the intraguild
predation of A cucumeris and O sauteri on the
other predators on bean leaves in absence or in
presence of their shared prey T palmi
2 MATERIALS AND METHODS
Thrips T palmi were reared on bean plants
Phaseolus vulgaris in a climatic-controlled room
(25 ± 2oC, 50 - 70% RH, 16 h light) Clean plant were grown in a climatic room (same regime) until they were 10-days old They were then placed in three separated closed cages: one cage for rearing thrips, one cage for rearing the
predator A cucumeris, and the other for rearing the minute pirate bug O sauteri When the thrips
populations developed well on bean plants, the
predator A cucumeris or O sauteri were released
(all stages were used to get enough numbers in a
short time) Predator A cucumeris culture, T
palmi and Orius sauteri were from the continuous
rearing in the Entomology laboratory After another four weeks, the populations were well developed and their numbers enough for being used in the experiments
2.1 Olfactometer experiment
Glass Petri dishes of 10 cm diameter are used
to study the response of adult female predators to volatiles The glass is divided into two parts with
a border When the lid is closed, these two parts are isolated from each other In the center of the border is a bridge, closed during incubation period and open during the experiment (Fig 1)
Bean leaf discs (diameter 2.5 cm) are placed
on wet cotton wool in a plastic container and infested each with 25 larvae and 25 adults of the
prey T palmi Primary leaves of two plants are
used to make the odour sources as equal as possible The next day, 5 predators are added to one
of the two leaf discs The leaf discs are used as odour source the next day, hence they are infested with thrips for 2 days, and one of the leaf discs has predators for 1 day
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Fig 1 Set-up with glass petridish diameter 10 cm In the centre is a border
with bridge, closed during incubation period and opened during experiment
Adult female predators are starved for 1-3 h
prior to the experiments This is done to motivate
the predators to seek for the prey (Ibrahim et al.,
2006)
Two bean leaf discs are placed opposite in a
glass Petri-dish An adult female predator is
released in the center of the petri dish (also a center
of bridge) Each individual is observed until she
reaches one of the two leaf discs during a
maximum time of 5 min, and is subsequently
removed In this way, each predator is tested
separately
2.2 Intraguild predation
It was measured the rates of intraguild
predation of adult females on heteroconspecific
larvae or adult females in the absence of the shared
prey Bean leaf discs (=2.5 cm) are placed on wet
cotton wool in a plastic container Twenty five
larvae or five adults of the female predator of one
species are added to clean leaf discs Five adult
females of the other species are added the same
day One day later, live and killed individuals are counted Experiments are done in a climate room ((25 ± 20C; 16 h light) The experiment is replicated forty times
3 RESULTS AND DISCUSSION
It is known that plants under insect attack emit specific volatiles (Dicke et al., 1990; Turling et al., 1990; Vet and Dicke, 1992; Takabayashi and Dicke, 1996 - cited by Jetske and Dicke 2005) Herbivore-induced plant volatiles are used as foraging cues by a diverse range of arthropod carnivore species, including parasitoid wasps, and predatory bugs and mites (Jeske and Dicke, 2005)
so it was expected that under attack of thrips T
palmi bean plants (in the experiment bean leaves)
will emit a specific blend of chemicals to attract
predators such as A cucumeris and O sauteri It is
also knows that insects often release specific chemicals or excretes for marking territories to prevent other insects from coming in their occupied
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territories so expectation was that the chemicals
emitted from bean leaf with prey patches (with T
palmi only) are different from the chemicals
emitted from bean leaf with prey patches and
predator (A cucumeris or O sauteri) The goal of
the olfactometer experiment was to check how A
cucumeris and O sauteri responded to these two
groups of chemicals
In the first experiment, in 19 of total 40
replicates the predator A cucumeris went to the
bean leaf with prey T palmi and predator O sauteri
and in 21 replicates A cucumeris went to the bean
leaf with T palmi only The result showed that the
predator A cucumeris has no preference in the
choice of two bean leaves: the bean leaf with or
without the heteroconspecific predator O sauteri (P
= 0.874, non - parametric binomial test)
When O sauteri was given a choice between
the bean leaf with T palmi and A cucumeris and
the bean leaf with T palmi only, O sauteri also did
not discriminate between the two sides In 22 of 40
replicates O sauteri went to the bean leaf with T
palmi and A cucumeris and in 18 replicates O
sauteri went to the side with T palmi only on the
bean leaf There is no significance as P = 0.635,
non-parametric binomial test (see the figure 02 for detail)
In experiments in 1997 - 1999, Janssen and her
staff found that Phytoseiulus persimilis avoids plants
with the two-spotted spider mites and conspecifics, whereas it does not avoid plants with two-spotted
spider mites and Neoseiulus californicus Ibrahim et
al (2006) also found that P persimilis did not avoid
the volatiles emanating from bean leaves with spider
mites and the heteroconspecific predator N
californicus In my experiment the result showed the
same trend for A cucumeris and O sauteri as they
did not show any preference in the choice between bean leaves with prey only and bean leaves with prey and the other heteroconspecific predators The answer for that maybe that both predators do not recognize the volatiles emitted from the other predator or they recognize these volatiles but do not recognize the other predators as a threat In fact, they
are not biologically closely related species: A
cucumeris attacks only immature larvae thrips and
consume one larva during 24 hours while O sauteri
can kill much more (hundreds) and all stages of
thrips, so A cucumeris is not a food competitor for
O sauteri
Proportion of predators on both sides of the olfactometer
Fig 2 The response of A cucumeris (bar 2) when offered a choice between odours from leaves with thrips and leaves with thrips and the other predator O sauteri in an olfactometer and the response of
O sauteri when offered a choice between odours from leaves with thrips and leaves with thrips and the
other predator A cucumeris (bar 1)
0.55
0.475
0.45 0.525
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
1
2
To prey patches with heterospecific predators
To prey patches with no heterospecific predators
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The second reason for the non - significant
preference maybe the set-up of the experiment: not
enough time for incubation (only 2 days for prey
and one day more for the predator) The third
reason may be that the experimental device was not
good enough: the volatiles from the two parts could
have been mixed during the period when putting
the predator in the releasing point It may have been
better to use an Y-tube olfactometer to study the
response of insects to chemicals emitted by plants
or animals However, these were not available in
the laboratory and there was not enough time to
acquire one
In the second experiment, 25 larvae of O
sauteri and 05 adult A cucumeris were released
together in one bean leaf in 40 replicates and after
one day it was found that in all replicates the
numbers of two predators remained the same There
were no mortalities and no escapes The result
indicates that there is no predation between two
predator species and it makes no sense to test the
intraguild predation between two predators in the
presence of their shared prey T palmi as planned in
the beginning The minute pirate bug O sauteri is
very big compared to the predatory mite A
cucumeris, and A cucumeris is very fast so it is
understandable that one is not a prey of the other
even in the absence of their shared prey The result
from the second experiment is in agreement with
the first, indicates that each predator does not
recognize the other as a threat of predation or food
competition
4 CONCLUSION
There is no negative effect when both
predators A cucumeris and O sauteri are released
in the field to control pests like the phytophagus
thrips T palmi When one predator does not
discriminate prey patches with or without the other
predator, the predator will establish itself in the
fields regardless of the presence of the other
predator Both predators can be released together in
one field to control pests such as T palmi because
there is no predation between two predators in the
case that the populations of the prey are low
Amblyseius cucumeris or O sauteri does not affect
the performance of the other in finding and killing harmful thrips in crops
Acknowledgements
First of all, I wish to thank Prof Dr Arnold Van Huis and Prof Dr Nguyen Van Dinh for supervising
my research project at the Entomology department, Hanoi Agricultural University and for correcting this report Many thanks to Assoc Prof Dr Nguyen Thi Kim Oanh, Prof Dr Ha Quang Hung
I would like to thank the Vietnamese Government, Ministry of Training and Education; and Project 322 for financially supporting my MSc Programme
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