Evaluation of terbufos/permethrin and terbufos/cypermethrin combinations as soil insecticides

Christopher John Voglewede, Purdue University

Abstract

Corn rootworms (Coleoptera: Chrysomelidae, Diabrotica spp.) and black cutworm larvae (Lepidoptera: Noctuidae, Agrotis ipsilon [Hufnagel]) are key pests of corn (Zea mays L.). Over a billion dollars per year is lost from crop loss and control costs. Soil insecticides applied to the corn crop at planting are the main control measures to prevent pest losses. These studies were conducted to evaluate the effectiveness of novel terbufos/pyrethroid blends as soil insecticides against damage from corn rootworm and black cutworm larvae and observe the degradation rates of terbufos, permethrin, and cypermethrin in agricultural soils. Terbufos/pyrethroid blends did not cause phytotoxicity to young corn plants. The terbufos/pyrethroid blends did not consistently outperform the terbufos, treatments, suggesting that the addition of pyrethroids to terbufos, will not consistently enhance rootworm control. The terbufos/pyrethroid combinations reduced percent leaf feeding and percent cut plants when compared to the untreated in all experiments. The 559 mg/m rates of terbufos/permethrin and terbufos/cypermethrin provided equivalent to or better control than the industry standards for percent feeding and percent cut plants. The 372 mg/m rates of terbufos/permethrin, terbufos/cypermethrin, permethrin, and cypermethrin provided inconsistent control. The 559 mg/m rates of terbufos/permethrin and terbufos/cypermethrin provided better control than terbufos in only one location. Although not statistically significant, the 559 mg/m rates of terbufos/pyrethroid blends usually had lower percent feeding than terbufos alone. Mean residues of terbufos and terbufos sulfone declined by 97.8% and 89.3% at the Ballard location and 76.5% and 86.3% at the Gobel location over 37 days. Estimated half-lives of terbufos were approximately 14 and 28 days for the Ballard and Gobel locations, respectively. Mean residues of permethrin isomers declined by 95.6% and 92.8% at the Ballard and Gobel locations, respectively, over 37 days. Estimated half-lives of permethrin isomers were 14 to 28 days for both locations. Mean residues of cypermethrin showed inconsistent degradation rates at the Ballard and Gobel locations. Because of the variability in the data, half-lives of cypermethrin isomers could not be estimated. The degradation rates of terbufos and permethrin in these studies were consistent with the degradation rates in the literature.

Degree

Ph.D.

Advisors

Edwards, Purdue University.

Subject Area

Entomology|Agronomy

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