Conservation of natural enemies in cotton: role of insect growth regulators in management of Bemisia tabaci

Abstract

Field studies were conducted from 1997 to 1999 to contrast the effects of two insect growth regulators (IGRs) and conventional insecticides on natural enemy conservation in cotton within the context of alternative management strategies for Bemisia tabaci (Gennadius). Compared with an untreated control, insecticide regimes based on the initial use of the IGR buprofezin or pyriproxyfen reduced densities of eight predator taxa out of 20 examined in at least one year, including common species such as Geocoris punctipes (Say), Nabis alternatus Parshley, Chrysoperla carnea s.l., and the empidid fly Drapetis nr. divergens. Patterns of predator and pest population change relative to IGR application dates suggest that factors other than direct toxic effects, such as reduction in prey availability, were likely involved. In comparison, the use of conventional insecticides reduced populations of nearly all the predatory taxa examined in most years, including those affected by IGRs, with the impact being greater and more immediate in all cases. Predator:prey ratios were significantly increased by the use of IGRs compared with both the untreated control and a conventional insecticide regime in most instances. The application of conventional insecticides for suppression of Lygus hesperus Knight, another key pest in the system, in a split-plot design reduced densities of most predator taxa and diminished the selective advantage of the IGRs. Rates of parasitism by aphelinid parasitoids (Eretmocerus eremicus Rose and Zolnerowich and Encarsia spp.) were generally low and did not vary consistently due to B. tabaci or L. hesperus insecticide regimes over the three years. Our 3-year study demonstrates the more selective action of buprofezin and pyriproxyfen in an effective integrated control system for B. tabaci. The use of these IGRs could further facilitate biologically based management in cotton production systems. Published by Elsevier Inc.

Pest management based on petroleum spray oil in navel orange orchard in Ganzhou, South China

“…Field studies of insecticide effects on natural enemies integrate many factors, including direct toxicological effects and reduction in prey availability (Naranjo et al 2004). Our results supported the previous hypothesis (Beattie et al 1995b) that Petroleum spray oils can be selective in protecting the natural enemy components.…”

Farm-scale evaluation of the impacts of transgenic cotton on biodiversity, pesticide use, and yield

“…1b). Insect growth regulators (IGRs), which are considered less harmful to nontarget arthropods than broad-spectrum insecticides, are used in Arizona for controlling the sweet potato whitefly (Bemisia tabaci) in cotton (11)(12)(13)(14). Use of IGRs did not differ significantly between transgenic and nonTr cotton ( Table 2, which is published as supporting information on the PNAS web site).…”

Ecological Determinants of Bemisia tabaci Resistance to Insecticides

“…Not only are the new products more effective control agents at reduced rates compared to conventional insecticides, their generally narrower activity spectra make possible a more finessed approach to pest management. As the Israeli and Arizona examples have shown with the IGRs buprofezin and pyriproxyfen, treatments have proven less destructive to biological control agents while simultaneously providing better direct control of B. tabaci (Naranjo et al 2004). The thorough research that identified the bio-residual phenomenon for the IGRs has yet to be performed for newer MoAs, but preliminary findings suggest that some also show a high degree of compatibility with beneficial insects.…”