Predatory mites Amblyseius swirskii (Athias-Henriot) and A. cucumeris (Oudemans) as potential biocontrol agents of Thrips palmi Karny – pest of field cucumber in south Florida

The melon thrips Thrips palmi Karny (Thysanoptera: Thripidae), is an economically important pest of various greenhouse and field crops in south Florida. It is a pest of Southeast Asia origin from where it spread to the rest of Asia, North Africa, Australia, Central and South America, and the Caribbean. In Florida it was first observed in 1990. Feeding by this pest can result in damaged leaves, flowers and fruits. Leaves may become yellow or bronze in color due to feeding and finally it dries and dies off. Due to spraying by calendar schedule in south Florida,T. palmi populations have developed resistance to insecticides, emphasizing the need to introduce biocontrol agents. In the past, predatory mites have shown promising results in other thrips species under green house study. In order to verify if these mites are effective in suppressing T. palmi we evaluated the efficacy of two mites, Amblyseius swirskii (Athias-Henriot) and A. cucumeris (Oudemans) in field cucumber. We found that thrips count in plots treated with A. swirskii was significantly lower than plots treated with A. cucumeris. There was no significant difference in the thrips count from the plots treated with A. cucumeris and non treated control plots. The reproduction rate of A. swirskii was higher than that of A. cucumeris indicated by the higher mite eggs and nymphs in treated plots. The results indicate that A. swirskii can play an important role in regulating T. palmi.