Efficacy of silk channel injections with insecticides for management of Lepidopteran pests of sweet corn

Authors: SPARKS, A - University Of Georgia; GADAL, L - National Institute Of Agronomy, Food Science And Environment (AGROSUP); Ni, Xinzhi

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2015
Publication Date: 8/1/2015
Citation: Sparks, A.N., Gadal, L., Ni, X. 2015. Efficacy of silk channel injections with insecticides for management of Lepidopteran pests of sweet corn. Journal of Economic Entomology. 108(4):1869-1874.

Interpretive Summary: The key ear-feeding pests of sweet corn production in Georgia are the corn earworm, which is also known as cotton bollworm, and the fall armyworm. Control of these pests typically requires intensive insecticide application scheme, starting from silk emergence until harvest, with commercial growers frequently spraying daily. This level of insecticide use presents problems for small growers, particularly for “pick-your-own” operations. Injection of oil into the silk channel five to eight days after initial silking has been used to suppress damage by these insects. Initial work with this technique in Georgia provided poor results. Subsequently, a series of experiments was conducted to evaluate the efficacy of silk channel injections as an application methodology for insecticides. A single application of synthetic insecticide, at greatly reduced rates as compared to common foliar applications, provided excellent control of lepidopteran insects attacking the ear tip and also suppressed damage by sap beetles. Although this methodology is labor intensive, it only requires a single application of insecticide at only one third of the lowest labeled rates. The silk channel injection can be conducted approximately two weeks prior to harvest, as compared to potential daily applications at full rates up to the day of harvest. This methodology is not likely to eliminate the need for foliar applications because of other insect pests, but would greatly reduce the number of applications required. This methodology may prove particularly useful for small acreage growers.

Technical Abstract: The primary Lepidopteran pests of sweet corn in Georgia are the corn earworm, Helicoverpa zea (Boddie), and the fall armyworm, Spodoptera frugiperda (J.E. Smith). Control of these pests typically requires multiple insecticide applications from first silking until harvest, with commercial growers frequently spraying daily. This level of insecticide use presents problems for small growers, particularly for “pick-your-own” operations. Injection of oil into the silk channel five to eight days after silking initiation has been used to suppress damage by these insects. Initial work with this technique in Georgia provided poor results. Subsequently, a series of experiments was conducted to evaluate the efficacy of silk channel injections as an application methodology for insecticides. A single application of synthetic insecticide, at greatly reduced rates as compared to common foliar applications, provided excellent control of lepidopteran insects attacking the ear tip and suppressed damage by sap beetles. While this methodology is labor intensive, it requires a single application of insecticide at reduced rates applied approximately two weeks prior to harvest, as compared to potential daily applications at full rates up to the day of harvest. This methodology is not likely to eliminate the need for foliar applications because of other insect pests, but would greatly reduce the number of applications required. This methodology may prove particularly useful for small acreage growers.