The potential of Amblyseius swirskii as biocontrol agent for Aculops lycopersici on tomatoes

Abstract: The tomato russet mite (TRM), Aculops lycopersici (Massee) is an important pest of tomatoes. So far no effective biological control strategy has been developed for this pest. The generalist phytoseiid predatory mite Amblyseius swirskii (Athias-Henriot) showed high oviposition rates when feeding on A. lycopersici as prey on tomato leaf discs and was therefore evaluated as potential biological control agent of russet mite on tomato plants. Amblyseius swirskii established and multiplied when it was released on small tomato plants that were heavilyinfested with TRM. Thereafter, the efficiency of A. swirskii in TRM control was tested in a semi-field experiment with bigger tomato plants. The predatory mites were released at two different intervals after infestation of the plants with A. lycopersici; i.e. 6 days and 20 days after the release of the TRM. In both cases the predatory mite density remained low throughout the experiment and the tomato russet mite density was not reduced as compared to the untreated control. The A. lycopersici reached a maximum density of 135 to 145 motile stages per leaflet seven weeks after infestation. In tomato crops phytoseiid predatory mites are usually less effective as biological control agents than on other plants, because tomato plants have glandular trichomes which negatively affect their performance. The density of trichomes is much lower on areas of the tomato plant that are heavily infested with A. lycopersici than on uninfested or slightly infested areas. The perspectives of predatory mites as potential biological control agents of A. lycopersici will be discussed.