LAUSR

Abstract Bactericera cockerelli (Sulc) is an important pest of solanaceous crops and a vector of the pathogen Candidatus Liberibacter solanacearum . Biological control of this pest has been attempted using either the parasitoid, Tamarixia triozae (Burks), or the predatory bug, Dicyphus hesperus (Knight), but never in combination. Through a series of laboratory experiments we investigated their combined use. In choice and no-choice experiments we evaluated the ability of D. hesperus to i) prey on different developmental instars of B. cockerelli and ii) prey on B. cockerelli nymphs previously parasitized by T. triozae . In choice and no-choice experiments D. hesperus preyed on more second and third instar B. cockerelli nymphs than fourth instar nymphs; in the no-choice experiment egg predation was similar to predation of fourth instar nymphs but almost no eggs were eaten when other instars were available in the choice experiment. In choice and no-choice experiments D. hesperus ate more B. cockerelli nymphs that contained T. triozae eggs, than nymphs containing T. triozae larvae; almost no nymphs containing T. triozae pupae were eaten. When both natural enemies were released simultaneously in B. cockerelli populations both parasitism and predation levels were reduced relative to when each species was released alone. However, the overall mortality of B. cockerelli obtained when both species were released together was additive. The implications of our results for the combined use of these two natural enemies for biological control of B. cockerelli in protected agriculture is discussed.