The effect of combined application of the entomopathogenic fungus Metarhizium anisopliae and the release of predatory mite Phytoseiulus longipes for the control of the spider mite Tetranychus evansi on tomato

The entomopathogenic fungus Metarhizium anisopliae (Ma) and the predatory mite Phytoseiulus longipes (Pl) are both potential biocontrol agents of the tomato spider mite Tetranychus evansi. The combination of the two agents may enhance biological control of T. evansi if there is no antagonistic effect. Here, we evaluated the effect of combining the application of Ma and Pl in the control of T. evansi under screenhouse and field conditions on tomato crops. The acaricide abamectin was included as a control. Spray applications of Ma and abamectin, and release of Pl in the screenhouse significantly reduced mite population density among motile (P < 0.0001) and egg stages (P < 0.0001) of T. evansi as compared to the control. There was also significant reduction in mite population density in the field but only with spray applications of Ma and abamectin, and Ma + Pl treatments among motile (P < 0.0001) and egg stages (P < 0.0001). In the screenhouse experiment, leaf damage was significantly lower in all the treatments than in the control. In the field, leaf damage was significantly higher in the control and Pl alone treatments than in the other treatments. The combination of both Ma and Pl resulted in a reduction of T. evansi numbers in the screenhouse and field, but did not consistently differ significantly from Ma alone. Based on these results, we conclude that there is no benefit of combining M. anisopliae and P. longipes for the control of T. evansi in tomato crops.