Integrating entomopathogens and synthetic insecticides for the management of whitefly (Hemiptera: Aleyrodidae) on vegetables.

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Citation abstract

The sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is one of the major pests infesting squash (Cucurbita spp.). The present study examined the interactions between combined applications of 2 insecticides, imidacloprid and cyantraniliprole, with 2 entomopathogenic fungi (EPF), Beauveria bassiana (GHA strain) and Cordyceps javanica (wfGA17 strain), across 8 squash cultivars infested with B. tabaci. The insecticides were tested for compatibility with EPF at three concentrations using in vitro bioassays. A compatible rate based on the survival of the EPF was subsequently selected for evaluating the lethality against B. tabaci. The combined application of EPF and either of the insecticides resulted in higher B. tabaci nymphal mortality than when either agent was applied alone. Although some reduction in fungal viability was observed, some combinations still produced enhanced efficacy, particularly with imidacloprid. Among all treatments, the combinations involving imidacloprid yielded the highest percentage mortality. The nature of EPF-chemical interactions (synergy, additivity, or antagonism) varied by cultivar. Additive interactions were consistently recorded on the cultivars Early Summer, Fortune, Gray Summer, and Green Eclipse where both EPF species showed enhanced effectiveness when combined with imidacloprid, and to a similar extent, with cyantraniliprole. However, antagonistic interactions were found when C. javanica was combined with cyantraniliprole on the cultivars, Gentry, Grey Summer, Lioness, and Respect, or B. bassiana and imidacloprid on the cultivar Golden glory. Overall, the results emphasized the potential of combining EPF with selective insecticides and the importance of cultivar-specific responses in optimizing B. tabaci control.