The suitability of Diorhabda elongata (Coleoptera: Chrysomelidae) as a food source for Coccinella septempunctata (Coleoptera: Coccinellidae)

The first open-field releases of Diorhabda elongata Brullé, a biological control agent of the invasive shrub, saltcedar, began in 2001. Currently released in fourteen states and recently approved for release in Oklahoma, the beetles have established with mixed success. One of the main reasons thought to be hindering establishment is predation. The ladybeetle Coccinella septempunctata, a prominent natural enemy, has been recorded in saltcedar stands at the Salt Plains National Wildlife Refuge and thought to be a possible predator of the biological control agent. To test the suitability of D. elongata as a food source for this natural enemy, a C. septempunctata lab colony was established from two field populations (Lahoma and Jet, OK). All four larval instars and the adult stage of the Coccinellid were fed an adequate but not unlimited diet of either Diorhabda elongata eggs or a corresponding amount of Acerythosiphon pisum, a known suitable food source. The survival, development times (in days) and elliptical body area (mm²=[Π x .5(body length) x .5(body width)]) of the larvae were tracked. Adults were tested in mating pairs and the number of eggs and the percent progeny survival were compared between food sources.