Euseius addoensis addoensis,an effective predator of citrus thrips,Scirtothrips aurantii,in the eastern Cape Province of South Africa

The predacious mite,Euseius addoensis addoensis (McMurtry) (Acari: Phytoseiidae), significantly (P<0.05) reduced scarring on Palmer Navel oranges,Citrus sinensis (L.) Osbeck, caused by the citrus thrips,Scirtothrips aurantii Faure (Thysanoptera: Thripidae). A chemical exclusion method employing dicofol was used to determine the effect of the predator and numbers ofS. aurantii were monitored on sticky yellow traps. At two sites where numbers of citrus thrips and predacious mites were high, the percentage fruit culled from export quality due to damage byS. aurantii was reduced from 25.5 to 15.5% and from 32.7 to 18.7% by predacious mite activity.Euseius a. addoensis sometimes prevented damage from exceeding 1% cull and was most effective when mean numbers exceeded one mite per inside leaf at petal fall. The best correlation between numbers of mites and the percentage fruit culled at harvest was –0.96 at the location with the highest number of citrus thrips. Tartar emetic (0.398% a.i.) plus sugar (0.4% a.i.) treatments for citrus thrips were slightly detrimental toE. a. addoensis populations but their numbers soon recovered. An alternative treatment, methiocarb 0.016% a.i. plus sugar (0.4% a.i.), almost eliminated the predacious mites and resulted in more citrus thrips damage (10.7% cull) than in the adjacent untreated control (0.2% cull) which contained predacious mites.