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Title: SEASONAL AND ANNUAL DYNAMICS OF BEMISIA TABACI (GENN.) POPULATION RESPONSES TO INSECTICIDES IN CALIFORNIA (HOMOPTERA: ALEYRODIDAE)

Author
item Castle, Steven
item PRABHAKER, NILIMA - UNIV OF CA, RIVERSIDE, CA
item Henneberry, Thomas
item TOSCANO, NICK - UNIV OF CA, RIVERSIDE, CA

Submitted to: Entomology International Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/1/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The succession of host crops of B. tabaci (SPW) throughout the annual cycle has made possible year-round monitoring of responses to insecticides. Beginning in 1993, populations have been sampled seasonally from three crops: spring muskmelons, summer cotton and fall-winter cruciferous crops. The bioassay method used was 7.6x12.7 cm yellow cards lightly coated with Tanglefoot, then sprayed with a concentration of insecticide representing one of 5-6 doses for treatment. Collections of adult SPW are facilitated by their attraction to yellow, alighting on the sticky cards after being flushed from crop foliage. Mortality is scored 24 h later under a microscope. No progression to higher resistance levels was observed over three consecutive years (1993-95) of monitoring adult SPW populations. Regressions of LC50s against time for each year's bioassay data indicated a lower mean response in 1995 compared to 1993 for bifenthrin and endosulfan in spite of continued use of both insecticides. Negative slopes significantly different from zero for the cotton crop LC50s indicated higher susceptibilities at the end of the cotton season, whereas the opposite was true for the melon crop bioassay data. Differences in LC50s between crop seasons suggested the potential role of host plant effects on adult whitefly susceptibilities to certain insecticides. Interseasonal dynamics of LC50s suggest the involvement of ecological factors in addition to genetic factors in responses of SPW populations to insecticides.