The Inevitable Fate of Tetranychus urticae on Tomato Plants Treated with Entomopathogenic Fungi and Spinosad.

Abstract

Tetranychus urticae (Acari: Tetranychidae) is a pervasive and damaging mite pest of tomato crops, leading to important economic losses globally. This study evaluated the acaricidal efficacy of spinosad, alone and in combination with Beauveria bassiana (Bb) WG-21 and Metarhizium robertsii (Mr) WG-04, in the laboratory (application to tomato leaf discs) and greenhouse (application to tomato plants), considering mortality and establishment, respectively. The combination treatments of Bb WG-21 or Mr WG-04 with spinosad achieved 100% mortality of T. urticae nymphs within 2 days on leaf discs, while individual applications of each control agent resulted in lower mortalities, ranging between 62.91 and 86.25% after 3 days. The paired treatment of Mr WG-04 + spinosad killed all exposed adults within 5 d, while that of Bb WG-21 + spinosad achieved the same results after 7 d. However, spinosad, Mr WG-04, and Bb WG-21 alone killed ≥77.08% of adults after 7 d. In the greenhouse, the combination treatment of WG-04 + spinosad deterred the presence of T. urticae (adults, immatures, and eggs) on either surface of the tomato leaves, while Bb WG-21 + spinosad suppressed the populations only on the adaxial surface. These findings indicate that combined treatments of the tested EPF + spinosad, especially Mr WG-04, on tomato plants under greenhouse conditions can provide substantially enhanced control of T. urticae life stages compared to each treatment applied alone.