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Greenhouse whitefly
 The
greenhouse whitefly is a common pest of houseplants and greenhouse plants.
This insect has a host range of more than 250 ornamental and vegetable
plants, including the poinsettia, begonia, hibiscus, aster, cucumber,
tomato, grape and bean.
 Adult whiteflies are white and fly in a weak, random manor. Adult
females typically lay eggs on the newest leaves. Nymphs emerge in five to
seven days and flatten themselves against the leaf to feed. They suck sap
from the plant, stunting growth and causing the leaf to yellow or drop and
a general decline of plant vigor. A sooty mold can grow on the foliage of
plants from sticky honeydew excreted by whiteflies.
 Whitefly control outdoors is not necessary in Colorado; they do not
cause enough damage and they cannot survive the winter. Indoors or in
greenhouses, however, whitefly control is necessary. The immature stages
of the insect are inconspicuous and easily overlooked. The nymphs are
translucent and do not move from their feeding area. Preventing outbreaks
by not bringing infested plants inside is the best management tool.
Whiteflies are resistant to most traditional pesticides. Infested plants
in a greenhouse should be discarded. Yellow and white sticky traps placed
above host plants can either monitor or help control whitefly populations.
Parasitic wasps also are used as biological controls against whitefly.
insecticides effective against whitefly nymphs include horticultural oils,
neem-based chemicals and insecticidal soaps. Some plants, however, are
sensitive to soaps. Pyrethrins and related pyrethroid insecticides are the
best controls for adults.
For more information, see the following Colorado State Extension fact sheet(s).
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