Use of Isoelectric Focusing Electrophoresis to Evaluate Citrus Thrips (Thysanoptera: Thripidae) Predation by Euseius tularensis (Acari: Phytoseiidae)

Abstract

Predation of citrus red mite, Panonychus citri McGregor, and citrus thrips, Scirtothrips citri (Moulton), by adult female Euseius tularensis Congdon was studied in laboratory experiments. Hungry predaceous mites readily attacked and fed on both species. Red gut coloration and distension of the gastric cecae persisted for 24—48 h after feeding on a citrus red mite deutonymph, depending on temperature (16.1—29.4°C), and for up to 14 h after feeding on a larva at 22.8°C. Isoelectric focusing electrophoresis (IEF) and staining for phosphogluco-isomeraseenzymes was used to study predation on citrus thrips larvae. Predation on an average size 2nd-instar citrus thrips could be detected for 16—40h after feeding, depending on temperature, and for up to 12 h after feeding on a 1st instar with the predator held at 22.8°C. IEF was used to evaluate levels of citrus thrips predation by E. tularensis in 15 field samples, 5 each taken from San Joaquin Valley, southern interior Califomia, and coastal citrus groves shortly after petal fall. Citrus thrips predation was indicated in only 7 of 556 adult female E. tularensis sampled (1.3%). Contrary to popular belief, we question whether E. tularensis is a major factor in biologicalcontrol of citrus thrips. The IEF technique is also well suited for rapid screening of other potential citrus thrips predators.