Evaluating Predation of Megalurothrips Usitatus (Bagnall) (Thysanoptera: Thripidae) by Amblyseius Swirskii (Athias-Henriot) and Neoseiulus Cucumeris (Oudemans) (Acari: Phytoseiidae)

Abstract

Megalurothrips usitatus (Thysanoptera: Thripidae), a major pest of leguminous crops in the Asian tropics, was first reported in Florida in 2020 and has since spread across Central America and the Caribbean. To control M. usitatus, Florida snap bean growers face higher production costs from increased insecticide use. However, despite a heavy reliance on chemicals, significant crop losses continue. This ongoing challenge emphasizes the need for integrated approaches, such as biological control, to achieve more effective and sustainable management of M. usitatus. This study evaluated two commercial predatory mites, Amblyseius swirskii and Neoseiulus cucumeris (Mesostigmata: Phytoseiidae), as biological control agents against M. usitatus through leaf disk bioassays and growth room cage studies. In the leaf disk bioassays, both predators caused significant thrips larval mortality, consuming three to four first instar larvae daily over 96 hours. Daily oviposition rates were 1.07 for A. swirskii and 1.48 for N. cucumeris, with both predators showing high survival rates while feeding on M. usitatus. Growth room cage studies evaluated the potential of the predatory mites to control M. usitatus on Phaseolus vulgaris plants. Weekly evaluations over four weeks showed that A. swirskii significantly reduced M. usitatus population by approximately 75% by week 4, though not to satisfactory levels, resulting in significant plant damage. Neoseiulus cucumeris did not significantly reduce thrips populations compared to control plants. This study provides evidence that A. swirskii can reduce M. usitatus populations on P. vulgaris plants, but further research is needed to improve the effectiveness of the predator.

Keywords: biological control, Thrips control, Predatory mites, Invasive pest, IPM