Arthropod Pest and Natural Enemy Interactions: Can Pests Become Resistant to Natural Enemies?
Continuation of Can Pests Become Resistant to Natural Enemies?
Physical Defenses
Physical defense mechanisms include disturbance, movement, and falling off plants. Western flower thrips adults use their abdomen like a whip to strike predatory mites (analogous to Indiana Jones). This is the primary reason why the predatory mites, A. cucumeris and A. degenerans only attack the first instar larvae since they are easier to handle.
Arthropod pests that move abruptly can avoid attack or remove eggs laid on their bodies. For example, mealybugs will perform vigorous movements including wriggling and head jerking, which prevents them from being attacked by parasitoids such as Leptomastix dactylopii. Vigorous movements may also allow an arthropod pest to escape parasitoids or predators causing the natural enemies to forage elsewhere. The American serpentine leafminer, Liriomyza.trifolii performs vigorous movements that dislodge the eggs laid on their bodies by the parasitoid Diglyphus beginii.
Some insect pests avoid attack by either remaining still (motionless) or falling off plants. For example, some aphid species will remain still when approached by a parasitoid. Aphids may also use pheromones or emit odors that alert the population to remain motionless. Finally, aphids may fall off plants when a parasitoid or predator is nearby, which removes them from the immediate area. The aphids detect vibrations as natural enemies walk on the plant surface.
In Summary
This article has described in detail some of the behavioral and morphological, physiological, and physical defenses that arthropod or insect and mite pests use to avoid or prevent attack from natural enemies including parasitoids and predators. Despite this, natural enemies have evolved ways to circumvent these defenses or attack a more vulnerable life stage of an arthropod pest. This is one reason why it is important to select the appropriate natural enemy and release natural enemies early. Biological control has been used for many years and is still an effective, environmentally friendly way to deal with greenhouse arthropod pests.
About the Author: Dr. Raymond A. Cloyd is an Associate Professor and Extension Specialist in Ornamental Entomology and Integrated Pest Management for the Department of Entomology at Kansas State University (KSU). A “Bugologist.” He is both knowledgeable and approachable. Dr. Cloyd has previously published Pesticide Compatibility: Is It Really Possible? in our Bug Blog.
Additional Resources
Here are additional resources that may compliment this article.
- Learn more about noted arthropod pests (this site).
- Learn more about noted natural enemies (this site).
- See glossary for referenced terminology (this site).
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Mike Cherim responds:
Posted: April 2nd, 2009 at 7:00 am →
We’ve always held onto the belief that the only way pests could really develop a resistance to natural enemies was to evolve over time. What we didn’t take into consideration is that pests have been evolving over time all along and have always been at war with their enemies. Everything has enemies, and anything that does has defenses to its enemies. This includes plants. One of the best things a grower can do is to bolster their plants’ defenses against their natural enemies — namely plant pests — by keeping them healthy and growing vigorously. Thank you very much, Ray. This article is very insightful.