Tuesday, September 22, 2009

Pest of the Week - 9/22/09

Figure 1 Greenhouse Whitefly
Image from: University of California

Common name: Whitefly (Silverleaf, Greenhouse, Bandedwinged, Sweetpotato, and others)

Latin Name (in order of common names listed parenthetically above): Bemisia argentifolii Bellows & Perring, Trialeurodes vaporariorum (Westwood), Trialeurodes abutilonea (Haldeman), Bemisia tabaci (Gennadius)

Life Cycle: Overwinter in weeds and ornamental plants, multiple generations per year, adults lay eggs (10’s to 100’s at a time), four instars from egg to adult, first stage is crawler, remaining are stationary until adult stage, Greenhouse whitefly has circular pupae with flat top, resembling tuna fish can with filaments emerging from top of can, while Silverleaf and Sweetpotato pupae are convex and no flat top , use pupal or instar stages to ID species/strain , most species/strains of whitefly excrete and lay eggs in waxy residues left on leaf surfaces, entire generation can take as little as 16 days

Plants affected/Damage seen: Hundreds of different types to include but not limited to: Solanaceae, Cruciferae, Malvaceae, Luguminosae families; whitefly in the greenhouse will attack more plant species than if outside, stipule scarring seen, deformed leaf/blossom growth

Insect Habit: Piercing sucking mouthparts can transmit viruses readily, especially in a closed greenhouse, crawler stage moves to vein, inserts mouthparts and begins feeding, then stays immobile for the next three molts until emerging as adult

Control: Use yellow sticky cards and a hand lens to identify species or strain and to monitor populations, destroy heavily infested plants immediately, prune out heavily infested leaves or plant parts, dispose of vegetable plants as soon as harvest is over, inspect new transplants for infestations before planting in your garden, hoop house or greenhouse, encourage natural enemies (green lacewing, ladybeetle, big eyed bug, minute pirate bug, damsel bug), if infestation is severe, insecticides and introduced biological controls might be needed (PLEASE CHECK WITH YOUR LOCAL HORTICULTURAL EXTENSION AGENT REGARDING EFFECTIVE BIOLOGICAL AND CHEMICAL CONTROLS FOR YOUR AREA), resistance to insecticides has been found in whitefly populations due to multiple generations per growing season


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