Effect of Food Deprivation on Hydrilla Tip Mining Midge Survival and Subsequent Development

Abstract

Hydrilla, Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae), is an invasive aquatic macrophyte found in fresh water. The introduction of hydrilla by the aquarium plant trade has led to its invasion throughout much of the southern US and its current listing as a federal noxious weed. Hydrilla employs many pathways of reproduction and once established can rapidly fill the water column, impeding recreation and negatively affecting the environment. Waterways infested with hydrilla typically experience matting of vegetation at the surface that results in less light penetration, and changes in dissolved oxygen levels, which disturb native species richness and diversity. Efforts to minimize hydrilla populations include using biological control agents such as the hydrilla tip mining midge, Cricotopus lebetis Sublette (Diptera: Chironomidae). The larvae of C. lebetis feed on the apical meristem of hydrilla tips, disabling further vertical growth and forcing growth into a branched horizontal direction. Currently, a colony of C. lebetis is being mass-reared to augment midge populations throughout hydrilla-infested waters. In order to maintain colony viability for effective releases, midge eggs must be collected and placed on hydrilla before larvae exhaust endogenous nutrient reserves. To understand the effects of larval starvation on survival and subsequent development to adult eclosion, neonates at 0, 1, 2, and 3 d post-hatch were studied with and without access to food. Midge survival and adult eclosion decreased significantly after continued starvation post-hatch. Larvae starved for 2 d post-hatch did not eclose. Highest survival to adult eclosion occurred when midge larvae were placed on hydrilla as soon as they hatched (48 h post-oviposition). This study highlights fundamental information necessary for efficient midge rearing for effective biological control of hydrilla.