Crowd control: well established predator populations can reduce damageby tomato russet mite Aculops lycopersici (Acari: Eriophyidae)

Abstract: The tydeoids Homeopronematus anconai (Baker) and Pronematus ubiquitus(McGregor) occur naturally on tomato without being entrapped by the tomato trichomes andcan reach high densities when suitable pollen is supplied. They can feed on Aculops lycopersiciMassee, the tomato russet mite (TRM), an eriophyoid that causes severe damage to greenhousetomato plants. Homeopronematus anconai was first tested against TRM in short-termgreenhouse trials in a curative and preventative way with supplementation of Typha pollen. Thespecies was effective in reducing TRM damage, in particular when plants were well colonizedby the predatory mites before TRM introduction. In a short-term spring trial it preventedoutbreaks of the pest. In a longer trial, the efficacy of H. pronematus and P. ubiquitus on TRMwas compared to untreated control plants. TRM was not eradicated by the tydeoids, but the pestwas kept for weeks at low levels on plants that were densely colonized by the predatory mites.The evaluation of the two species revealed thus that high level tydeoid colonization can providetomato plants protection against A. lycopersici or that the symptoms can be postponed andstrongly reduced. Possibilities for an adequate preventative biocontrol strategy are discussed.