Ways to improve biocontrol of tomato russet mites using predatory mites

Abstract: The tomato russet mite (TRM) Aculops lycopersici is an increasing problem in greenhouse tomato production. So far no effective biological control agents for this pest are available. Generalist phytoseiid predatory mites develop well on TRM when placed on leaf disks in laboratory trials. However, it is difficult for predatory mites to build up populations on tomato plants containing low TRM densities, because glandular trichomes are present in abundance, reducing the foraging efficiency of predatory mites. In contrast, on plants heavily infested by TRM, glandular trichomes are largely destroyed, allowing easier establishment of phytoseiid species. Amblyseius limonicus, however, is able to build up a population on tomato plants with intact glandular trichomes. In cage trials we showed its ability to reduce TRM populations. Combining A. limonicus release with the application of vegetable oils, further reduced TRM populations. The performance of A. limonicus was further improved by selective breeding on tomato plants. Subsequent cage trials resulted in a significantly higher population of the adapted line of A. limonicus on tomato plants in comparison to the not-selected line of A. limonicus and A. swirskii after 2 and 4 weeks.