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Manipulation of Tritrophic Interactions for IPM

Manipulation of Tritrophic Interactions for IPM. Tri-trophic Interaction. Predator/parasitoids. Herbivores. Plants. Plants Interact With the Third Trophic Level. Chemically Morphologically. Multi-trophic interactions. Hyperparasitoid. Predator/parasitoids. Herbivores.

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Manipulation of Tritrophic Interactions for IPM

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  1. Manipulation of Tritrophic Interactions for IPM

  2. Tri-trophic Interaction Predator/parasitoids Herbivores Plants

  3. Plants Interact With the Third Trophic Level Chemically Morphologically

  4. Multi-trophic interactions Hyperparasitoid Predator/parasitoids Herbivores Plants

  5. The Slow Growth High Mortality Hypothesis

  6. Feeding on sub-optimal food produces an increase in insect herbivore developmental time.

  7. Increased developmental time in herbivores may increase vulnerability to natural enemies

  8. 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).

  9. 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.

  10. Studies Supporting the Hypothesis G.lineola - Develop longer on S.sasyclados - Predators attack more on S.dasyclados P.rapae - Develop longer on low N collards - Predators attack more on low N collards M.disstria - Develop longer on late budbreaks - Predators attack more on late budtbreaks

  11. Which Natural Enemies Have Been Considered to Test the Hypothesis? • Suite of predators. • Single parasitoid species. • Parasitoid community.

  12. Orgyia leucostigma Acer negundo Salix nigra

  13. 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.

  14. O. leucostigma developed faster on willow P<0.0001

  15. Female O.leucostigma on willow were heavier than on box elder. b c F F a a M M

  16. Percent Parasitism of O.leucostigma on two tree species Overall percent parasitism on Family Parasitoid species Box elder Willow 1. X2 = 11.83; P<0.001

  17. O. leucostigma developed faster in willow than in box elder. Overall parasitism in O.leucostigma was greater in willow than in box elder. In Summary

  18. Conclusion • The slow-growth-high-mortality hypothesis does not hold for O. leucostigma and its parasitoid community.

  19. Conclusion On a free feeding herbivore feeding on unrelated species. • Support: - One parasitoid species considered. • Fail: - A community of parasitoids considered.

  20. 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.

  21. Differential susceptibility of herbivores to natural enemies

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