Spider Mite Control in Corn, 1993

Abstract

Abstract Two tests, (1 for BGM and 1 for TSM) were established in a furrow irrigated corn field at the Southwest Kansas Research-Extension Center, Finney County, KS. In each test, treatments were arranged in a RCBD with 4 replications. Plots were 4 rows (10 ft) wide and 50 ft long with a 4-row (10 ft) border of untreated corn on each side and a 10 ft alley at each end. Treatments were applied on 12 and 13 Aug with a high clearance sprayer using a 10 ft boom with 3 nozzles directed at each row (one on each side of the row on 16 inch drop hoses directed at the ear zone and a third nozzle directed at the top of the plant). The sprayer was calibrated to deliver 20 gal/acre at 2 mph and 40 psi. In each plot 4 plants were flagged, 2 plants in each of 2 center rows. In the BGM test, sections of corn leaves infested with Banks grass mites, collected in Haskell Co., were placed in the leaf axil of the flagged plants. In the TSM test, sections of corn leaves infested with twospotted spider mites from the laboratory colony were placed in the leaf axil of the flagged plants. Pretreatment spider mite counts were made on 9 Aug by visually searching all leaves of the flagged plants for large (adult female) spider mites. Post-treatment counts were made on 17 and 18 Aug, 23 and 24 Aug and 1 and 2 Sep (approx. 5, 11 and 20 days after treatment (DAT) respectively) by searching every other leaf (one-half plant) except for the TSM Test on 2 Sep when only half of every other leaf (one quarter plant) was searched. All spider mite counts were converted to mites per plant for presentation. Grain yield was determined by machine harvesting 2 rows per plot and the gross weight was adjusted to 15.5% moisture and converted to bu/acre.