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Title: IMPROVED CONSERVATION OF NATURAL ENEMIES WITH SELECTIVE MANAGEMENT SYSTEMS FOR BEMISIA TABACI (HOMOPTERA: ALEYRODIDAE) IN COTTON

Author
item Naranjo, Steven
item Hagler, James
item ELLSWORTH, PETER - UOFA DEPT OF ENTOMOL

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2002
Publication Date: 9/1/2003
Citation: NARANJO, S.E., HAGLER, J.R., ELLSWORTH, P.C. IMPROVED CONSERVATION OF NATURAL ENEMIES WITH SELECTIVE MANAGEMENT SYSTEMS FOR BEMISIA TABACI (HOMOPTERA: ALEYRODIDAE) IN COTTON. BIOCONTROL SCIENCE AND TECHNOLOGY. 2003. 571-587

Interpretive Summary: Insecticides remain an important tactic for the control of sweetpotato whitefly in cotton. However, many conventional insecticides are toxic to natural enemies, leading to disruption of potential biological control. In 1996 the state of Arizona was granted an EPA emergency exemption for two new insecticides, both of them insect growth regulators (IGRs), for whitefly control. These IGRs have a narrower spectrum of activity; however published laboratory studies suggested that they can be toxic to various species of parasitoids and insect predators. In part, this study was initiated to evaluate the impact of these IGRs on natural enemies under a realistic commercial production setting. Large (2 h) replicated field plots examined management regimes based on the use of the two IGRs and compared them to an existing regime based on the rotation of conventional insecticides. All regimes were highly effective in suppressing whitefly populations. However, densities of 18 out of 20 taxa of arthropod predators were significantly higher in regimes using the IGRs. In addition, predator to prey ratios and rates of parasitism on whitefly were higher with the use of IGRs compared with conventional materials. Results demonstrate the selective action of these two IGRs and suggest that their use may enhance opportunities for conservation biological control in cotton systems affected by B. tabaci, especially relative to conventional insecticide alternatives.

Technical Abstract: A commercial-scale study was conducted in 1996 to evaluate strategies for pest management of Bemisia tabaci (Gennadius) in cotton involving different insecticide regimes, application method, and action thresholds. Here we examined the effects of the various management systems on the abundance and activity of native natural enemies. Population densities of 18 out of 20 taxa of arthropod predators were significantly higher in regimes initiated with the insect growth regulators (IGRs) buprofezin (chitin inhibitor) or pyriproxyfen (juvenile hormone analog) compared with a regime dependent on a rotation of conventional, broad-spectrum insecticides. There were no differences in predator density between the two IGR regimes, and generally no effects due to application method or action threshold level. Predator to prey ratios were significantly higher in regimes utilizing the two IGRs compared with the conventional regime, but were unaffected by application method or threshold level. Rates of parasitism by Eretmocerus eremicus Rose and Zolnerowich and Encarsia meritoria Gahan were higher in the IGR regimes compared with the conventional regime, but were unaffected by insecticide application method, or the action threshold used to trigger applications of the IGRs. Results demonstrate the selective action of these two IGRs and suggest that their use may enhance opportunities for conservation biological control in cotton systems affected by B. tabaci, especially relative to conventional insecticide alternatives.