Life-stage specific predatory efficiency of two generalist predators of Bemisia tabaci (Gennadius) on contrasting vegetable host plants

The sweet potato whitefly (SPW) Bemisia tabaci (Gennadius) is a pervasive and economically damaging invasive pest to global vegetable production systems. Current management strategies rely heavily on insecticides but increasing levels of insecticide resistance have raised serious concerns. As a result, there is growing interest in strengthening integrated pest management (IPM) programs by enhancing biological control through improved predator-pest interactions. Despite the well-established relevance of predator functional response modulation by multiple environmental factors, limited research has explored how host plant traits and prey developmental stage interact to influence the efficiency of generalist predators in vegetable systems. To address this gap, we evaluated the functional responses of two adult generalist predators, Hippodamia convergens (Guérin-Méneville) and Geocoris punctipes (Say), against six prey densities of second, third, and fourth instar SPW nymphs on two common vegetable crops: yellow summer squash (Cucurbita pepo) and snap bean (Phaseolus vulgaris). Overall, functional response parameters did not differ significantly between host plants. Predation was highest when predators were offered fourth instar SPW nymphs and lowest on second instar nymphs. Interestingly, the nymph stage appeared to alter the shape of the functional response, where both predators exhibited a Type III functional response to second-instar nymphs and Type II responses to third- and fourth-instar nymphs. Our findings showed that both H. convergens and G. punctipes exhibited similar functional responses across host plants, but the prey stage was important in predicting the shape of the functional response of predators.