Frankliniella occidentalis

The western flower thrips (Frankliniella occidentalis) is an important pest insect in agriculture. This species of thrips is native to North America but has spread to other continents including Europe, Australia, and South America via transport of infested plant material. It has over 500 host plants, including a large number of fruit, vegetable, and ornamental crops. The adult male is about 1 millimeter long; the female is slightly larger, about 1.4 millimeters in length. Most western flower thrips are female and reproduce by parthenogenesis. Males are rare. They are variable in color, with some color types more abundant in certain seasons. Colors vary from red to yellow to brown. Each adult is elongated and thin, with two pairs of long wings. The eggs are oval or kidney-shaped, white, and about 0.2 millimeters long. The nymph is yellowish in color with red eyes.

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The life cycle of the western flower thrips varies in length because the adult may live from two to five or more weeks and the nymph may live from five to 20 days. Each female may lay 40 to over 100 eggs in the tissues of the plant, often in the flower, but also in the fruit or foliage. The newly hatched nymph feeds on the plant for two of its instars, then falls off the plant to complete its other two instar stages. The insect damages the plant in several ways. The major damage is caused by the adult ovipositing in the plant tissue. The plant is also injured by feeding, which leaves holes and areas of silvery discoloration when the plant reacts to the insect's saliva. Nymphs feed heavily on new fruit just beginning to develop from the flower. The western flower thrips is also the major vector of tomato spotted wilt virus, a serious plant disease.

Western flower thrips is a year-round pest, but is less destructive during wet weather. Damage can be reduced by growing barriers of non-host plants around crops and by eliminating reservoir plants, plants that the thrips are especially attracted to, such as jimson weed. The thrips' natural enemies include bugs of genus Orius. Other agents show promise as biological pest control, including the fungus Metarhizium anisopliae.