16 Dec 2016

WhiteFly


Whiteflies are sap-sucking insects that are frequently abundant in vegetable and ornamental plantings.

Whiteflies are small, fly like insects with white coloured wings. Whitefly numbers grow dramatically in the heat, most strains are resistant to pesticides, and the pests infect a huge range of host plants including bedding plants, strawberries, tomatoes and poinsettias. Whitefly attack plants in hordes of hundreds and a severe attack can severely weaken a plant.

OVERVIEW

Whitefly eggs are spindle-shaped and stand vertically on the leaf surface. Eggs are deposited on the underside of leaves, sometimes in a circle or crescent shaped patterns. After hatching, the “crawler” stage moves about the plant looking for a good feeding site. A mature female can lay up to 200 eggs. Within about a week, the eggs hatch into flattened nymphs, called crawlers, that wander about the plant. Soon, they insert their mouthparts into the plant and begin to feed. The nymphs remain fixed to the plant and feed for about four weeks. After a pupa stage, the adults emerge and live for about one month. Within a population, all life stages are present, and generations often overlap

Whiteflies damage plants by sucking out plant juices. Because large amounts of sap can be removed, primarily by the developing nymphs, heavily infested plants can be seriously weakened and grow poorly. Leaves often turn yellow, appear dry and drop prematurely. Also, whiteflies suck out more plant juice than they can digest, and they excrete the excess as a sweet, sticky substance called honeydew. The honeydew covers leaf surfaces and acts as a growth medium for a black, sooty mold. Both the removal of plant juices and the presence of the black, sooty mold growing on the honeydew can interfere with photosynthesis. White flies have been found to also spread virus’