1998 ESA North Central Branch Meeting Abstract

80 EFFECTS OF ADJUVANTS ON RESIDUAL ACTIVITY OF A CUCURBITACIN CORN ROOTWORM ADULTICIDE. R. L. Pingel, Department of Biology, Olen Hall, Bradley University, Peoria IL 61625; M. R. McGuire, B. S. Shasha, and R. W. Behle, Bioactive Agents Research Unit, USDA-ARS-NCAUR, 1815 N. University, Peoria IL 61604

Areawide management of the corn rootworm (CRW), Diabrotica spp., focuses on managing adult beetles to decrease egg deposition and thus decrease the numbers of future larvae. The main management tool is a

commercial adulticide bait (Slam®) composed of a feeding stimulant (cucurbitacin), inert ingredients, and a small quantity of insecticide (carbaryl). The bait has a reported limited residual life that would decrease its effectiveness and economic practicality; however, the addition of adjuvants may improve coverage and resist wash-off after

rainfall. The objective of this research was to test the ability of several experimental adjuvants to extend the residual activity of the bait in the field. The following adjuvants were added to a suspension of the adulticide: gluten, gluten + urea, sodium lignate, potassium lignate, and the recommended commercial adjuvant Windbrake®). Two small-plot experiments with residual activity assayed in the laboratory indicated that lower concentrations (1% or less of spray volume) of the adjuvants were equally efficacious as 2 and 4% in maintaining activity after simulated rainfall. Results of an experiment conducted in cooperating growers' fields of continuous corn in northwestern Illinois (Whiteside Co.) revealed no increased residual activity of the bait from the addition

of 4 adjuvants. Relatively low and late rainfall during the postapplication period did not allow for a vigorous rainfastness test. The adulticide (with/without adjuvants), however, provided adequate management of adult corn rootworms: the number of CRW beetles captured declined to less than 2 per trap per day 5 days after treatment application and remained below the treatment threshold (6 CRW/trap/day) for approximately 3 weeks. In contrast, the average number of beetles captured in untreated plots during the same time period was 14.6 CRW/trap/day.

This paper will be presented on Monday.

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