Biological control of citrus thrips, Scirtothrips citri (Thysanoptera: Thripidae), in southern California citrus groves

Population dynamics and biological control of the citrus thrips, Scirtothrips citri (Moulton), was studied over a 3-year period on "Washington" navel orange, "Lisbon" lemon, and "Marsh" grapefruit near Corona (Riverside County), Calif. The native phytoseiid predator, Euseius hibisci (Chant), was excluded from experimental plots in citrus groves by spraying a residue of malathion in plot trees and those surrounding the plots. Subsequent mass release of this predator into these plots suppressed the citrus thrips below economic levels. Early spring populations of >0.50 E. hibisci per leaf on inland valley citrus groves of southern California responded numerically and functionally to second- and third-generation increases of S. citri . Dimethoate, methomyl, and parathion were extremely toxic to E. hibisci ; residual toxicity of chlorobenzilate and carbaryl to the predator 26 days posttreatment was comparable to the water control.