Common on houseplants, mealybugs can also be a problem outdoors in mild-winter areas. They're similar to scale insects and aphids. The name refers to the female's powdery wax coating, a shield that prevents insecticides from penetrating. In large colonies, mealybugs cause extensive damage to soft tissues of plants: leaves are distorted and yellowed, growth is stunted. They excrete honeydew, which attracts ants and can encourage sooty mold.
Daub mealybugs on houseplants with a swab dipped in rubbing alcohol. In the garden, dislodge them with jets of water or treat with soap spray or horticultural oil. Some natural predators such as ladybugs and lacewings consume mealybugs.
Chemical controls include acephate, diazinon, and malathion, but hold off on these if you want help from beneficials.