Cabbage Integrated Pest Management : An Ecological Guide.

Major Cabbage Insect Pests5.10 Whitefly – Bemisia tabaciBemisia tabaci is a very common species of whitefly. However, there are several other species, forexample Aleurodicus dispersus (spiraling whitefly), and Trialeurodes vaporariorum (common whitefly).Other English names: tobacco whitefly, cotton whitefly or sweet potato whitefly.White fly currently is known to attack over 500 species of plants representing 74 plant families. Theyhave been a particular problem on members of the squash family (squash, melons, cucumbers, pumpkins),tomato family (tomato, eggplant, potato), cotton family (cotton, okra, hibiscus), bean family (beans,soybean, peanuts), and many ornamental plants.In Cebu, in the Philippines, serious damage on cabbages by the whitefly Bemisia tabaci occurred duringthe dry season. Injudicious use of pesticides and favorable temperature led to whitefly outbreak in thearea (Ref. FAO-ICP progress report April 1996 – Feb 1999).Description and life cycleThe adult whitefly is very small: about 1 mm long, silvery-white in color and with wings of a waxy texture.It is found often on the underside of the foliage where it sucks the plant sap.When a plant containing whiteflies is shaken, a cloud of tiny flies flutter out but rapidly resettle. The adulthas 4 wings and is covered with a white, waxy bloom. Adults can fly for only short distances but may bedispersed over large areas by wind. Females usually lay their first eggs on the lower surface of the leaf onwhich they emerged, but soon move upwards to young leaves. The female may lay 100 or more eggs.The egg is pear-shaped and about 0.2 mm long. It stands upright on the leaf. The eggs are anchored bya stalk which penetrates the leaf through a small hole made by the female. Water can pass from the leafinto the egg, and during dry periods when there are high numbers of eggs, the plant may become waterstressed.Eggs are white when first laid but later turn brown. Early in the season, eggs are laid singly butlater they are laid in groups. They hatch in about 7 days.When the nymphs hatch they only move a very short distance before settling down again and starting tofeed. Once a feeding site is selected the nymphs do not move. All the nymphal instars are greenishwhite,oval and scale-like. The last instar (the so-called “pupa”) is about 0.7 mm long and the red eyes of1. Egg (actual size about 0.24 mm long)2. & 3. Top and side view of 1 st stage nymph4. 4 th stage nymph (actual size about 0.75 mm long)adult whitefly(from Kerruishet al. 1994)103 Cabbage Ecological Guide - 2000