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The spider mitesTetranychus evansiBaker & Pritchard andTetranychus urticaeKoch (Acari: Tetranychidae) are key tomato pests worldwide. Biological control of spider mites using phytoseiid predatory mites remains challenging. The glandular trichomes on the tomato leaves and stem severely hamper the movement and establishment of the predatory mites. As a result, smaller predatory mites, able to thrive under the sticky heads of the glandular trichomes, have gained much interest. As some iolinid predatory mites were reported to feed on spider mites, we investigated the potential ofPronematus ubiquitusMcGregor to control bothT. urticaeandT. evansion tomato plants. On whole tomato plants,P. ubiquituswas able to suppress populations ofT. urticae, but not ofT. evansi. Based on the marginal number of spider mites killed in laboratory trials, the observed biocontrol effect on full tomato plants might not be due to direct predation but to a plant-mediated indirect impact. The oviposition ofT. urticaewas found to be significantly lower on tomato leaflets pre-exposed toP. ubiquitusas compared to non-exposed leaflets. The oviposition rate ofT. evansiwas not affected by previous exposure of the tomato host plant toP. ubiquitus. We demonstrated thatP. ubiquitusreduces the population growth ofT. urticaeon tomato plants. Further large-scale field trials need to confirm the findings of the present study. |
