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Euseius tularensis by Elizabeth Grafton-Cardwell, Department of Entomology, University of California, Riverside. Stationed at the Kearney Agricultural Center, 9240 S. Riverbend Ave., Parlier, CA 93648. This predatory mite is an important control agent of citrus red mite and citrus thrips in San Joaquin Valley, California citrus orchards. A closely related species, E. hibisci, is common in the southern citrus growing region of California. E. tularensis prefers to inhabit citrus and E. hibisci prefers to inhabit avocados.
Adults are pear-shaped and very shiny. They are white when feeding on pollen, yellow when feeding on citrus thrips, and red when they feed on citrus red mite. They avoid direct sunlight and when held on a leaf in the sun they will run rapidly down the main vein or across the leaf.
Habitat Citrus
Pests Attacked Primarily citrus red mite and citrus thrips, however, two-spotted spider mite, immature stages of scale insects and whitefly nymphs are also fed upon. This predatory mite also feeds on pollen and leaf sap.
Life Cycle E. tularensis overwinters as adults on the sucker shoots in the center of citrus trees. This predatory mite responds to the leaf texture and nutrition and is most abundant when new flush appears in the tree in the spring and fall. New citrus flush is rapidly followed by flowers, petal fall, and fruit development. Thus, the predatory mites are present when citrus thrips are damaging the fruit. Adults hunt along the leaf midveins in the shade in the day, under the calyx of the developing fruit, and over the entire fruit leaf surface toward nightfall. Total development time, from egg to adult, is 6-10 days, at 78-80°F. Females live about 30 days and lay 17 to 27 eggs, depending on the type of food they have available.
Relative Effectiveness Because this predatory mite is a generalist in its feeding habits, it does not target any particular pest and so it may not regulate their numbers below an economic threshold. Populations of 0.5 to 1.0 per leaf help to reduce citrus red mite and citrus thrips populations.
Pesticide Susceptibility Various San Joaquin Valley populations of E. tularensis have developed resistance to many organophosphate insecticides especially chlorpyrifos. They are still very sensitive to many carbamates (methomyl, formetanate hydrochloride) and pyrethroids used for citrus thrips, caterpillars, and scale control in citrus. Compatible, soft pesticides are sabadilla, spinosad, or spinetoram for citrus thrips control and narrow range petroleum oil, pyriproxyfen, and applaud for California red scale control.
Commercial Availability This predator is not available commercially. Because of its need for small amounts of leaf sap, it must be reared on a leaf surface. Its numbers naturally increase in citrus when broad spectrum pesticides are avoided.
References Congdon, B. D. and J. A. McMurtry. 1985. Biosystematics of Euseius on California citrus and avocado with the description of a new species (Acari: Phytoseiidae). Int. J. Acarol. 11: 23-30.
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