Soil Treatments with Insecticides for Control of the Eye Gnats Hippelates collusor and H. hermsi1

Abstract

Hippelates gnats breed predominantly in loose, cultivated soils, and one approach to their control is through soil treatments. The effectiveness of aldrin and other soil insecticides was investigated in the field. Aldrin and heptachlor sprays and granules within the range of practical dosages produced moderate initial control of Hippelates gnats but gave no significant reduction in gnat breeding after a lapse of 7 to 10 months. Dieldrin was not tested for its initial effectiveness, but at moderate dosages gave no control of gnats 7 months after application. Thiodan^® (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9- methano-2,4,3-benzodioxathiepin-3-oxide) at the highest applied dosage (6.2 lbs. per acre) was ineffective, and results with toxaphene were inconclusive. DDT was the only insecticide among the materials tested that gave a high degree of initial control of Hippelates collusor (Townsend). This material, when applied at 13 pounds actual toxicant per acre, gave 95% reduction of the emerging gnats initially. The long-term residual effectiveness of this material is not yet known.