Functional response and prey stage preference of *Delphastus catalinae* and *D. pallidus* (Coleoptera: Coccinellidae) on *Bemisia tabaci* (Hemiptera: Aleyrodidae)

Abstract

Considering the importance of natural enemies in the integrated management programme of Bemisia tabaci (Gennadius), in the current study we evaluated the biocontrol potential of two predatory beetles Delphastus catalinae Horn and D. pallidus LeConte against Middle Eastern Asia Minor 1 (MEAM1 or biotype B) and Mediterranean (MED or biotype Q) whiteflies, the two most notorious representatives of the B. tabaci species complex. The functional responses of two predators at prey densities ranging from 20 to 120 whitefly eggs/leaf disc, and prey-stage preferences with different ratios of whitefly eggs and nymphs of two predatory beetles were investigated under laboratory conditions. Both beetle species showed Type II functional response with respect to MEAM1 and MED eggs, determined by the logistic regression model. Based on the observed predation parameters (handling time, attack rate, and the number of eggs consumed), D. catalinae seemed to be a more suitable biocontrol candidate for whitefly pests. Results indicated that both the beetle species preferred whitefly eggs over the early nymphal instars and they could consume >50 eggs per day. Although these findings are promising, their feeding potential needs to be evaluated further under greenhouse and semi-field conditions to confirm their efficacy against MEAM1 and MED whitefly.