Greenhouse Whitefly

Greenhouse whitefly adults lay masses of minute, elliptical eggs on the undersides of leaves. After hatching, the whitefly larva goes through four instars of development, the last of which is often called the "pupal" stage and is most identifiable by long, waxy filaments around the margin of the body and red eyes. The adult emerges from this state and is a tiny, white insect that is about 0.06 inches (1.5 mm) long. It has four membranous wings that are held parallel to the top of the body and covered with white wax. The wings partially fold over one another. Adult whiteflies occur in dense colonies on the undersides of leaves in newer growth of caneberries and fly when the leaves are disturbed.

Development of the greenhouse whitefly from egg to adult takes as little as 18 days, if temperatures and host plant conditions are ideal. Ideal temperatures for fastest development are between 80° and 90°F.

Greenhouse whiteflies can be a problem in raspberry and blackberry crops. They tend to favor succulent, actively growing plant tissue. They damage plants by feeding on the sap, which reduces plant vigor but most harm is caused by the exudation of sticky honeydew. When this exudate is deposited on fruits, it makes the fruit less attractive and marketable. Honeydew also promotes the growth of black sooty mold on fruits and leaves, which sharply reduces fruit quality. Although greenhouse whitefly is capable of transmitting viruses, it has not been associated with any significant viruses in caneberries grown in California.

A management program in caneberries for whitefly can benefit from an integrated approach that incorporates cultural, biological, and chemical methods. Avoid disruptions of native predator and parasitoid populations, along with applying cultural controls whenever possible.

Natural enemies of whitefly include Encarsia, Eretmocerus, Prospaltella, bigeyed bugs, minute pirate bugs, and lacewing larvae. Up to 40% of whitefly can be parasitized and predated in certain areas of the Central Coast. However, releases of large numbers of predators or parasites for whitefly control have not been successful in California caneberries.

Normal pruning of primocanes and removal of dead floricanes in caneberries can reduce the buildup of greenhouse whitefly populations. It is important to note that the host range of greenhouse whitefly is quite broad and includes alfalfa, avocados, beans, cucumbers, eggplants, grapes, lettuce, melons, peas, peppers, potatoes, strawberries, tomatoes, and many ornamental crops. Monitor whitefly activity in adjacent fields, and initiate any control measures when those crops are being destroyed or degraded to the point where whiteflies begin to migrate out.

It can be useful to establish a program that denies whitefly populations any viable host for a period of time. Although such gaps in cropping may be difficult to justify economically, they will significantly reduce whitefly populations.

Cultural and biological controls are organically acceptable methods, as is the use of insecticidal soaps and neem oil.

There is as of yet no treatment threshold for whitefly in caneberry, but chemical treatments may be necessary when there are moderate to large populations of whiteflies, resulting in honeydew on fruit during periods of warmer weather.