Egg - Virtually nonexistent in the South, the eggs of these aphids are minute, ovate, and black and are laid only in the fall.
Nymph - The wingless nymphs resemble the adults in color and shape but are smaller.
Host Plants - The cabbage aphid feeds primarily on broccoli, brussels sprouts, cabbage, cauliflower, collards, kale, and radish. Mustard is rarely infested. The turnip aphid typically infests mustard, radish, shepherdspurse, turnip, and watercress. It also injures other crucifers, particularly in their seedling stage.
Damage - Aphids cluster on the underside of leaves and suck sap causing infested foliage to curl, wilt, or become distorted. Some infested plants are soon killed; others grow slowly, are stunted, and produce small unmarketable heads.
Life History - In North Carolina, cabbage and turnip aphids continue to feed and breed at reduced rates throughout the winter. Collards are an important overwintering host plant. As warm weather returns, aphid activity increases. Wingless female adults produce large numbers of live progeny (50 to 100) without mating, which all develop into females. Periodically, winged females develop and fly to new host plants. Favored by moderate temperatures and dry weather, reproduction continues in this manner throughout summer. As many as 30 to 45 annual generations occur along the Gulf Coast though not quite so many are produced in North Carolina.
Chemical control of aphid infestations is often necessary. For up-to-date recommendations, consult the current North Carolina Agricultural Chemicals Manual.
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