Intraguild interactions between an oligophagous predator, Delphastus catalinae (Coleoptera: Coccinellidae), and a parasitoid, Encarsia sophia (Hymenoptera: Aphelinidae), of Bemisia tabaci (Homoptera: Aleyrodidae)

Abstract

The intraguild interactions between two natural enemies of Bemisia tabaci (Gennadius), an oligophagous predator, Delphastus catalinae (Horn), and a parasitoid, Encarsia sophia (Girault & Dodd), associated with predation, parasitization, host feeding, and suppression of B. tabaci populations were determined on cabbage under laboratory and greenhouse conditions. We conducted two laboratory experiments: a no-choice test of prey consumption by three larval instars and adult D. catalinae foraging for either whitefly fourth instar nymphs or whitefly nymphs containing second or third larval instar or pupal parasitoids of E. sophia; and a choice test, in which three larval instars or adult D. catalinae were allowed to forage for the above prey, presented simultaneously. We also conducted a mesocosm experiment under greenhouse conditions in which a low (20 females) or high (40 females) release of E. sophia adults, a low (6) or high (12) release of D. catalinae adults, a combined release with both predators and parasitoids at the low rate (20 parasitoids and 6 predators), and the experiments were performed on caged plants infested experimentally with whiteflies. In no-choice and choice experiments, predation was generally lower on the whitefly nymphs containing E. sophia pupae than on larval stages or on unparasitized whitefly nymphs. In choice tests, adult D. catalinae did not discriminate between prey types. In both choice and no-choice tests, second instar D. catalinae larvae tended to discriminate against whitefly nymphs containing parasitoid larvae, and the third and fourth instar predator larvae tended to attack less the whitefly nymphs containing parasitoid pupae than larvae. In the mesocosm experiment, the results indicate that D. catalinae did not avoid feeding on B. tabaci nymphs with larval stages of E. sophia and numbers of whitefly nymphs killed by E. sophia were lower in the presence of D. catalinae. However, whitefly immatures on cabbage leaves were significantly less abundant in each of the three treatments with the presence of D. catalinae as compared with treatments that did not include the predators.