Natural enemy impacts on Bemisia tabaci (MEAM1) dominate plant quality effects in the cotton system

1. Plant quality (bottom-up effects) and natural enemies (top-down effects) affect herbivore performance. Furthermore, plant quality can also influence the impact of natural enemies. 2. Lower plant quality through reduced irrigation increased the abundance of the cryptic species from the Bemisia tabaci complex [hereafter B. tabaci Middle East Asia Minor 1 (MEAM1)], but not its natural enemies on cotton. It was therefore predicted that lower plant quality would diminish the impact of natural enemies in regulating this herbivore. 3. Over three cotton seasons, plant quality was manipulated via differential irrigation and natural enemy abundance with insecticides. Life tables were used to evaluate the impact of these factors on mortality of immature B. tabaci (MEAM1) over nine generations. 4. Mortality of B. tabaci (MEAM1) was consistently affected by natural enemies but not by plant quality. This pattern was driven by high levels of sucking predation, which was the primary (key) factor associated with changes in immature mortality across all irrigation and natural enemy treatments. Dislodgement (chewing predation and weather) and parasitism contributed as key factors in some cases. Analyses also showed that elimination of sucking predation and dislodgement would have the greatest effect on overall mortality. 5. The top-down effects of natural enemies had dominant effects on populations of B. tabaci (MEAM1) relative to the bottom-up effects of plant quality. Effects were primarily due to native generalist arthropod predators and not more host-specific aphelinid parasitoids. The findings of this study demonstrate the important role of arthropod predators in population suppression and validate the importance of conservation biological control in this system for effective pest control.Maricopa Agricultural Center; Arizona Pest Management Center; USDA-National Institute for Food and Agriculture Extension IPM program; USDA-ARS; Cotton Incorporated; Arizona Cotton Growers Association; Cotton FoundationsThis article is a U.S. Government work and is in the public domain in the USA.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu