During the past few years numerous claims have been made for a yield enhancement effect resulting from early-season applications of the ovicide chlordimeform [N-(4-chloro-0-toly)-N-N-dimethylformamidinel to cotton (Gossypium hirsutum L.). No specific reasons have been given or the reported yield increases, but a physiological effect of the ovicide is inferred.

Field studies were conducted at Stoneville, Mississippi in 1979, 1980 1981, and 1982 to evaluate the effects of multiple applications of chlordimeform on growth and development of cotton 'DES-56'. Treatments consisted of an untreated control, chlordimeform at 0.15 lb a.i./acre, the insecticide fenvalerate [cyano-(3 phenoxyphenyl)methyl 4-chloro- -(1-methylethyl) benzeneacetatel at 0.1 lb a.i./acre, and chlordimeform plus fenvalerate at 0.15 4- 0.1 lb a.i./acre. Treatments were initiated at, or just prior to, the pinhead-square stage of plant development and applied at 7-day intervals until the plants began to bloom. A total of 4 to 6 application were made each year. Treatments were replicated 6 times in a randomized block design and applied to 4-row plots 40 feet long. All data were taken from the two center rows of each plot.