Origin:
This is a common native species in the western U.S. A related species, Frankliniella tritici, is found throughout North America.
Biology:
This thrips causes damage to the foliage of many plants, including bedding plants and flowers, some annual vegetables and strawberries, grapes, stonefruits, and a variety of trees and shrubs. Feeding is heaviest on the underside of the leaves, leading to distorted foliage, discoloration, and ultimately yellowing and loss of the leaf. Feeding on young fruits will lead to surface blemishes that also make the fruit unacceptable for sale. Males are rare or even unknown and reproduction is by parthenogenesis. The larva and adult both feed by piercing the plant surface and ingesting plant fluids. They also may “bite” people when they are on the skin.
Identification:
Foliage where thrips are feeding will have tiny dark globules of fluid over them, a substance given off by the insects that serves to deter predators. Adults are extremely small, light yellow in color with a darker stripe down the middle of the upper side, and pale wings that are held straight back over the abdomen while at rest, giving the insect the appearance of only a thin line. Under high magnification the 4 wings can be seen to have only a narrow wing with long hairs extending off both the front and the bottom margins. There also are thick, bristle-like hairs extending from the tip of the abdomen.
Characteristicts Important to Control:
Very few natural controls exist for thrips, and this leads to a difficult reliance on insecticides. Some species of thrips are actually predatory and feed on other thrips and mites, so proper identification is helpful in deciding whether or not to apply an insecticide. Because the eggs are inserted into the plant tissue they may be protected from topical sprays. Treatments include insecticide soap, insecticidal oils, and contact or systemic insecticides, but these often are minimally effective due to the insect feeding on the underside of the foliage, their numbers and mobility, and tiny size. Sprays should concentrate on the undersides of the leaves and repeat applications may be expected.
