Grape whitefly normally appears when the vineyard is close to chaparral or ornamental shrubs that are suitable as overwintering hosts. The only known evergreen host shrub is the coffeeberry, Rhamnus californica Eschscholtz, native to southwest Oregon, California, Arizona, and New Mexico. It is a dark green shrub, commonly 1 to 3 m (3 to 10 feet) high, with a green berry that turns red and finally black when ripe. Species of Crataegus, deciduous hawthorn, are known as the pest's summer hosts. other deciduous hosts are Vitis vinifera L., European grapes, and Vitis spp., American grapes.
Injury on commercial grapes is chiefly caused by sticky excrement soiling fruit. A black, sooty fungus develops on both fruit and foliage, causing serious smutting. Under high-population pressures, foliage and fruit turn black. This can cause major problems at harvest, and heavy insect-feeding pressure over time may also adversely affect the grapevine itself.
Blodgett S. 1992. Grape Whitefly. Pages 245-246 in: Grape Pest Management, 2nd edition. University of |