Control of Larvae of the Western and Northern Corn Rootworm with Liquid Starter Fertilizer-Insecticide Combinations and the Influence of Depth of Placement12

Abstract

Carbofuran, ethoprop, fonofos, fensulfothion, CGA 12223 (O-[5-chloro-l-(l methylethyl)-1 H-1,2,4,-triazol-3-yl]O, O-diethyl phosphorothioate), and SRA 12869 (phosphoroamidothioic acid, N-isopropyl-O-ethyl ester, O-ester with isopropyl salicylate) were applied at planting time (1.2 oz AI/1000 ft of row) as mixtures with starter fertilizer (10-36-0 at 100 lb/acre) in split-boot placement at seed depth for control of larvae of western, Diabrotica virgifera LeConte, and northern, D. longicornis (Say), corn rootworms. When placed at seed depth the starter fertilizer-insecticide mixtures resulted in significantly less ( P =0.05) root damage than in the untreated rows. Carbofuran and CCA 1223 were the only mixtures that resulted in control equivalent to the soil insecticide treatment standard (carbofuran 10G in a 7-in. band over the row in front of the press wheel at planting time) every year of the study. Applications of carbofuran or fonofos as mixtures with starter fertilizer resulted in significantly less root protection when applied in split-boot placement 2 in. below the seed rather than at seed depth.