Impact of refrigeration on eggs of the hydrilla tip mining midge Cricotopus lebetis (Diptera: Chironomidae): Larval hatch rate and subsequent development

摘要

Hydrilla verticillata (L.f.) Royle, Hydrocharitaceae (hereafter hydrilla) is a federally listed noxious weed and one of the worst invasive aquatic plants in the United States, with millions of dollars spent annually to control infestations in all types of water bodies. Hydrilla invades natural and artificial ecosystems, producing surface mats that clog waterways, prevent sunlight penetration, and alter biodiversity. The adventive hydrilla tip mining midge (Cricotopus lebetis Sublette; Diptera: Chironomidae) is a potential biocontrol agent for hydrilla. During the larval stage, the hydrilla tip mining midge mines into the apical meristems of hydrilla, inhibiting vertical growth and restricting surface mat formation. The hydrilla tip mining midge iscurrently being mass-reared in a laboratory colony to augment established populations in Florida. Eggs often are refrigerated to delay development or for transportation to field release sites. Therefore, it is important to understand consequences of cold storage on hatch rates, development, and adult eclosion. Egg masses that were stored in a refrigerator at 5 C for 1, 2, 4, 7, 14, and 21 d were tested for larval hatch rate, development to pupation, and adult eclosion. Hatch rate and adult eclosion decreased significantly after 7 and 2 d refrigeration, respectively. Pupal mortality increased significantly after 2 d. Results of this study showed that cold storage of eggs destined for field release should be avoided. If storage is required, the number of eggs released should be increased to compensate for cold-induced mortality. This study will contribute to successful biocontrol of hydrilla by improving hydrilla tip mining midge rearing and release protocols.