Designing a more effective hydrilla biocontrol agent, cricotopus lebetis

The midge, Cricotopus lebetis, is a biocontrol agent for the invasive weed hydrilla. Introduced through the aquarium industry in the 1950s, hydrilla has invaded Florida’s natural ecosystems producing surface mats which clog waterways, prevent sunlight penetration and compete with native plants. As a larvae, the midge mines into the apical meristem preventing further vertical growth and restricting surface mat formation. Using this method of biocontrol along with herbicides, mechanical cultivation and cultural control will reduce hydrilla. Improving rearing and release of C. lebetis will enhance the biocontrol aspect of an integrated pest management program. Egg hatch and subsequent development of eggs held at 5^oC for 1, 2, 4, 7, 14, and 21 days were analyzed. Hatch success decreased significantly after 7 days at 5^oC. Final adult emergence decreased significantly after 1 day at 5^oC. Intraspecific larval competition using 1, 2, 3 and 4 larvae per hydrilla tip was also evaluated. Average rate of emergence increased as competition was reduced, with one larvae per tip having the highest emergence rate. Storage at 5°C should be limited or compensated accordingly for reduced adult emergence. Intraspecific larval competition can be reduced by using the correct ratio of midge eggs to tips of hydrilla.