Adult Emergence Patterns and Insecticidal Control of Mexican Corn Rootworm in the Lower Gulf Coast Region of Texas, 1987

Abstract

Abstract A large-plot field study was conducted on a commercial farm near Goliad to evaluate soil insecticides for control of Mexican corn rootworms in conventional-till corn. Corn had been planted at this test site in each of the 9 growing seasons previous to the study reported here. Seven treatments and an untreated check were compared in 6-row, 500-ft plots of corn planted 9 Mar in 38-inch rows. Treatments and the untreated check were replicated 3 times in a randomized complete block design. Using Gandy applicator boxes, soil insecticides were applied in a T-band at planting time. Edaphic conditions at planting time consisted of 21% water (by weight) in the top 4 inches of soil and a temperature of 65°F at 4 inches below soil surface. The soil type was a sandy clay loam with an organic matter content of 1.3%. Efficacy of treatments was determined by counting plants at 3 sites (13.8 ft/site) in each plot 1 month after date of planting, by collecting plants from 6 sites in each plot (1 plant/site) and rating the roots for degree of rootworm feeding damage by the Iowa State University 6-category system (1, no visible damage, to 6, 3 or more nodes destroyed), and by harvesting each plot with a commercial machine for yield analysis. Relative infestation levels of rootworms in untreated and insecticide-treated corn were determined by capturing soil-emerged adults in cages placed in each untreated and Counter-treated plot (2 cages/plot). The cages (36 × lOinches) were placed over the plants were inspected weekly for rootworm adults; plants in the cages were maintained at a height of about 16 inches.