Cherry-Tree Fly Infestation

Description

• Black-colored adult cherry fruit flies have yellow heads and legs and are less than ¼ inch long, even smaller than houseflies. The center of the back has a distinct yellow spot. The cherry fruit fly, most abundant of the three species, is distinguished with three white bands on the abdomen of males and four on the females. The 1-mm-long eggs are white and the emerging larvae are white and legless. The pupa is golden brown to brown and about 4 mm long.

Infestation Period

• Cherry trees are infested with the flies during late May and early June. The presence of flies tends to vary with weather conditions like rainfall and temperature. Moderate temperatures and even rainfall are among the favorable weather conditions where the upper 1 inch of soil remains consistently wet for an extended period. Extended droughts and dry soil reduce the emergence of the maggots.

Damage

• Female fruit flies lay single eggs just under the skin of the fruit, creating inconspicuous, small scars. The eggs hatch in about five days. Dimples form around the puncture on the green fruit. The larvae feed inside the fruit, causing the fruit to separate from the pit. The fruit flesh turns brown and the skin over the feeding site shrivels. Worm-infested fruit is prone to the brown-rot fungus (Monilinia spp.). Late varieties of cherry suffer more damage from fruit flies than the early varieties.

Control

• The pests breed in large numbers on untreated, abandoned trees from where they migrate to infest healthy trees. It is best to remove such primary sources of infestation, as this significantly reduces pest population, especially near orchards. Introduce natural predators such as the braconid wasp and ichneuonid wasp in infested trees growing at home. Natural predators are not effective in controlling infestation in commercial orchards. Time the application of insecticide carefully for optimal control. Spray trees seven days following the emergence of the first fly. Early fruit varieties should be showing a slight hint of color. Recommended insecticides include malathion, carbaryl, spinosad and permethrin.