manipulation of tritrophic interactions for ipm. tri-trophic interaction plants herbivores...
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Manipulation of Tritrophic Interactions for IPM
Tri-trophic Interaction
Plants
Herbivores
Predator/parasitoids
Plants Interact With the Third Plants Interact With the Third Trophic LevelTrophic Level
ChemicallyChemically MorphologicallyMorphologically
Multi-trophic interactions
Plants
Herbivores
Predator/parasitoids
Hyperparasitoid
The Slow Growth High Mortality Hypothesis
• Feeding on sub-optimal food produces an increase in insect herbivore developmental time.
• Increased developmental time in herbivores may increase vulnerability to natural enemies
The Slow-Growth-High-Mortality Hypothesis
• Prolonged larval development of herbivores results in greater vulnerability and thus greater mortality due to natural enemies.
(Clancy and Price 1987).
Tests Have Produced Mixed Results
• Support:
- Free feeding herbivores.
- Feeding on same or related plant species.
• Fail:
- Concealed feeding herbivores.
- Feeding on unrelated plant species.
G.lineolaG.lineola
- Predators attack more on S.dasyclados
- Develop longer on S.sasyclados
P.rapae
M.disstria
- Develop longer on low N collards
- Predators attack more on low N collards
- Develop longer on late budbreaks
- Predators attack more on late budtbreaks
Studies Supporting the Hypothesis
Which Natural Enemies Have Been Considered to Test the
Hypothesis?
• Suite of predators.
• Single parasitoid species.
• Parasitoid community.
Acer negundo
Salix nigraSalix nigra
Orgyia leucostigmaOrgyia leucostigma
Experimental Protocol
• Rear O. leucostigma on willow and box elder.
• Measure development time and adult mass on willow and box elder.
• Use 7-year data base to determine percent parasitism of O.leucostigma on willow and box elder.
O. leucostigma developed faster on willow
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29
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33
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Willow Box Elder
Diet
Ave
rag
e d
eve
lop
me
nt
tim
e (
in d
ays)
A
BP<0.0001
Female O.leucostigma on willow were heavier than on box elder.
0
50
100
150
200
250
300
350
Willow Box Elder
Diet
Wei
gh
t (m
g)
B
A
CC
F F
M M
a a
b
c
Braconidae Cotesia delicata 19.35 80.65
Cotesia melanoscela 6.25 93.75
Cotesia sp 18.75 81.25
Meteorus hyphantriae 33.33 66.67
Meteorus sp 38.89 61.11
Ichneumonidae Casinaria limenitidis 50.00 50.00
Casinaria sp 85.71 14.29
Hyposoter fugitivus 50.00 50.00
Eulophidae Elachertus sp 33.33 66.67
Tachinidae Carcelia amplexa 50.00 50.00
TOTAL 11 30.00 70.00
Braconidae Cotesia delicata 19.35 80.65
Cotesia melanoscela 6.25 93.75
Cotesia sp 18.75 81.25
Meteorus hyphantriae 33.33 66.67
Meteorus sp 38.89 61.11
Ichneumonidae Casinaria limenitidis 50.00 50.00
Casinaria sp 85.71 14.29
Hyposoter fugitivus 50.00 50.00
Eulophidae Elachertus sp 33.33 66.67
Tachinidae Carcelia amplexa 50.00 50.00
TOTAL 11 30.00 70.00
FamilyFamily Parasitoid speciesParasitoid speciesOverall percent parasitism onOverall percent parasitism on
Box elderBox elder WillowWillow
1. X2 = 11.83; P<0.001
Percent Parasitism of Percent Parasitism of O.leucostigmaO.leucostigma on two tree species on two tree species
In Summary
• O. leucostigma developed faster in willow than in box elder.
• Overall parasitism in O.leucostigma was greater in willow than in box elder.
Conclusion
• The slow-growth-high-mortality hypothesis does not hold for O. leucostigma and its parasitoid community.
Conclusion
On a free feeding herbivore feeding on On a free feeding herbivore feeding on unrelated species.unrelated species.
• Support:
- One parasitoid species considered.
• Fail:
- A community of parasitoids considered.
Conclusion
• The effect of host plant quality on individual species of natural enemies might differ significantly from the effect of host plant quality on the natural enemy community.
Differential susceptibility of herbivores to natural enemies