Field experiments were conducted in 1989 to evaluate the influence of application timing, spray volume, adjuvants, and interactions with other pesticides on broadleaf weed control and cotton response to KIH-8921 (an experimental over-the-top herbicide). Determining interactions of these variables may reduce the likelihood of crop injury and/or inadequate weed control.

KTH-8921 was applied at 0.05, 0.10, and 0.15 lb ai/acre at the cotyledon to 2-leaf stage and the 5- to 7-leaf stage of cotton and weed growth. Fluometuran and MSMA also were included as over-the-top comparative treatments at 0.84 and 1. 5 lb/acre, respectively. Weed species included pitted morningglory, palmleaf morningglory, smallflower morningglory, ivyleaf morningglory, and velvetleaf. Treatments were applied in 20 gpa at 23 psi. over-the-top treatments contained a non-ionic surfactant (0.25% v/v).

Field experiments were conducted to evaluate effects of spray volume and adjuvants on weed and crop response. Weed response was determined with KIH-8921 applied at 0.02, 0.05, and 0.15 lb/acre in all possible combinations of no adjuvant, crop oil concentrate (1.0% v/v), and surfactant (0.25% v/v) in spray volumes of 10, 25, and 40 gpa. Species evaluated were pitted morningglory, entireleaf morningglory, and tall morningglory. In a separate experiment, cotton 'Stoneville 8251 response was evaluated only with 0.15 lb/acre rate.

Effects of aldicarb, disulfoton, and phorate (in-furrow insecticide treatments) on cotton 'Deltapine 50' tolerance to KIH-8921 were evaluated. Insecticides were applied at 1.0 lb ai/acre. KIH-8921 was applied at 0.15 lb/acre at the V3 stage of cotton growth. Interaction of foliar insecticides and KIH-8921 was evaluated in a factorial arrangement with KIH-8921 (0.05, 0.10, 0.15 lb/acre) applied in all possible combinations with no insecticide, acephate, carbaryl, and dimethoate at rates of 0, 0.20, 0.25, and 1.0 lb/acre, respectively. A nonionic surfactant was used with all treatments. Cotton 'Stoneville 825' response was evaluated only with KIH8921 applied at 0.15 lb/acre.

KIH-8921 at all rates and timings provided at least 94% control of the species evaluated except tall morningglory, which appeared less susceptible at the later application stage and with the lower rates at the earlier application timing. Control of all species except tall 'morningglory was greater than control with MSMA or fluometuron. Spray volume had no effect on efficacy or cotton response. Use of surfactant or crop oil concentrate improved tall morningglory control over no adjuvant, and crop oil was more effective than surfactant at the low rate. Pitted morningglory and entire leaf morningglory were controlled greater than 95% regardless of rate, adjuvant, or spray volume. No adverse interaction occurred with tank mixtures of KIH8921 and dimethoate or acephate. Carbaryl reduced morningglory control with KIH-8921 at the lower application rate. Cotton yield was not adversely affected by the foliar and in-furrow insecticides evaluated.