Effects of the miticide hexythiazox on biology of Galendromus flumenis (Acari: Phytoseiidae)

The Banks grass mite, Oligonychus pratensis (Banks) (Acari: Tetranychidae), is a major pest of dates. The miticide hexythiazox (Savey (R) 50 DF) is the current industry standard for Banks grass mite management on dates. However, sole reliance on hexythiazox as a single control strategy may lead to resistance in the mite population. Incorporating biological control into the Banks grass mite management on dates is a step towards a more integrated programme. The predatory mite, Galendromus flumenis (Chant), is the most abundant predator and the only phytoseiid species on date bunches. Conservation of G. flumenis is essential for a successful integrated mite management programme, and it is important to understand the impact of hexythiazox on the biological control of Banks grass mite by G. flumenis. For this purpose, the toxic effects of the recommended field rate of hexythiazox on the development of different immature stages and the fecundity of adult females of G. flumenis were evaluated. Laboratory bioassays were conducted in which predators were both treated topically by hexythiazox sprays and exposed to residues on the arena surface and on the sprayed prey. Mortality due to hexythiazox was 0.09% in eggs, 2.63% in larvae, 0.00% in protonymphs and 2.08% in adult females of G. flumenis. Hexythiazox did not have any significant effect on the fecundity of the treated females, hatch rate of the laid eggs, progeny development or sex ratio. Results suggest that hexythiazox would not disrupt the biological control of Banks grass mite by G. flumenis in the field.