Adult greenhouse whiteflies have their wings in an almost horizontal position. The wings are somewhat overlapping, covering almost the entire body. From a top down view, whiteflies have a triangular shape. Adult whiteflies and larvae are usually found on the underside of young leaves in the top of plants. Eggs are deposited in circles on the underside of the leaves in the top of the plant. Eggs start white, but will turn black in 2-3 days.

The first instar larvae have legs and antennae. They will search for a suitable spot to settle on the leaf. The second and third instar larvae are flat, translucent lightly yellow colored. They are barely visible with the naked eye and look somewhat like an armoured scale. During the fourth and final instar, larvae will fatten up and change into a box-like-shape with a ring of waxy threads around the body. In this stage the eyes are visible through the translucent skin. When the whitefly emerges, a white box-shaped skin with a t-shaped tear will remain.

Greenhouse whitefly damage

Larvae and adults cause crop damage. They suck plant saps from the phloem vessels of the plant, which causes little spots on the leaves. As a byproduct honeydew is excreted, which is usually more damaging than the actual feeding. The honeydew acts as a growth medium for black sooty mold fungus which will hamper photosynthesis and make products unsuitable for sale.

The third and potentially most damaging characteristic is the whitefly’s capability of transmitting plant viruses. Crops that whiteflies often transfer viruses to are for example potato, tomato or cucumber family members.