Laboratory Screening of Insecticides for Preventing Injury by the Wireworm Melanotus Communis (coleoptera: Elateridae) to Germinating Sugarcane

A laboratory bioassay was investigated for screening insecticides for preventing stand losses by the wireworm Melanotus communis (Gyllenhal) to germinating plant cane. For liquid materials, single-eye billets were dipped into different concentrations of a candidate insecticide and then planted in plastic containers of organic soil; wireworms were then introduced, airtight lids were placed onto the containers, and wireworm survival and damage were assessed 4 wk later. Tests with granular materials were similar except the containers were partially filled with untreated soil; 30 cc of soil treated with granular material were then added to the container; an untreated single-eye billet was placed onto this treated soil; an additional 30 cc of treated soil was then placed on and around the billet; and finally untreated soil was added to fill the container. Conditions inside the bioassay containers were suitable for germination and early growth of most cultivars. The airtight lids were advantageous from the standpoint of maintaining soil moisture. Among six candidate insecticides studied, bifenthrin 2EC, thiamethoxam 25WG, thiamethoxam 2G, and tefluthrin 3G each reduced damage by wireworms to germinating eyes of seed cane planted in organic soils. Wireworms frequently survived in containers of seed-pieces treated with these materials yet did not damage eyes before germination, indicating the materials repelled wireworms. However, germinated shoots of billets treated with these materials were sometimes injured by the surviving wireworms.