Tobacco Whitefly

Bemisia tabaci

B. tabaci is found on over 900 host plants on all continents except Antarctica. It reportedly transmits over a hundred virus species. The whitefly thrives in tropical, subtropical, and less predominately in temperate habitats. It is also a major pest of glasshouses. The adults are about 1 mm long; their body is sulphur-yellow in color, the wings are white, and the animal is entirely coated with a white, wax-like powder. The first instar nymph is about 0.3 mm in length and it moves about in search of a place to insert its mouthparts into the phloem.

Infestation is easily recognized by examining the undersides of leaves, where all stages of the insect can usually be found. At first, the damage consists of chlorotic spots. The leaves will start to show a yellow mosaic, with the green areas becoming ever smaller. Twisting of stems and curling of leaves may occur, and the plants may become stunted. Heavily-infested leaves often wilt and fall off. In addition to direct feeding, all stages damage the plants through abundant production of honeydew, which encourages the growth of sooty molds, and, most importantly, by the transmission of viruses.

The two most damaging biotypes of B. tabaci are the ‘B’ and ‘Q’ biotypes. The B-type has a worldwide distribution. The Q-type was largely restricted to the Mediterranean area but has recently been detected in the U.S.A and some regions of China. Biotype status can be diagnosed from esterase banding patterns using polyacrylamide gel electrophoresis (PAGE). B. tabaci has been shown to possess a high potential for resistance development.

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