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Title: THE EFFECT OF INSECTICIDE TREATMENTS IN COTTON FIELDS ON THE LEVELS OF PARASITISM OF BEMISIA TABACI (GENNADIUS) SL.

Author
item GERLING, DAN - UNIV OF TEL AVIV, ISRAEL
item Naranjo, Steven

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Bemisia tabaci is a pest of worldwide importance and is a key pest of cotton in Israel and the southwestern USA. Insecticides are the primary method of pest suppression in cotton for B. tabaci and other pests. Use of insecticides is usually associated with the destruction of the natural enemy complex and research is urgently needed to evaluate the compatibility yof chemical and biological control as components of an overall IPM system for B. tabaci. Studies were conducted in the Imperial Valley of California and in Israel to examine the impact of insecticide use on the activity of naturally-occurring whitefly parasitoids. Results showed that, in many cases, insecticide treatments had only a minor effect on levels of parasitism and that high levels of parasitism were sustained in insecticide-treated fields. Our findings suggest that the species of parasitoids we observed may be no more severely impacted by certain insecticides than nymphal whiteflies that serve as hosts. Nonetheless, reductions in parasitoid abundance may have important consequences for the biological control of B. tabaci over a larger area and judicious use of insecticides in commercial cotton fields is warranted.

Technical Abstract: Populations of whiteflies (Bemisia tabaci) and the rates at which they were parasitized in cotton fields in Israel and California were monitored over a number of years. Studies took place both in fields that were treated with insecticides and in untreated fields and permitted us to assess the influence of insecticidal treatments upon percentage parasitism. The results showed that, in many cases, insecticide treatments had only a mino effect on levels of parasitism and that high levels of parasitism were sustained in insecticide-treated fields. However, many repeated treatments, especially if monocrotophos was used, resulted in significant reductions in levels of parasitism in Israel. Our findings suggest that the species of parasitoids we observed may be no more severely impacted by certain insecticides than nymphal whiteflies that serve as hosts. Nonetheless, reductions in parasitoid abundance may have important consequences for the biological control of B. tabaci over a larger area an judicious use of insecticides in commercial cotton fields is warranted.