Mealy bugs usually affect house and greenhouse plants, but also outdoor shrubs, trees and some vegetable plants. The plant's leaves turn yellow and may wilt and die due to the sucking action of the insect. The plants themselves are rarely killed unless very heavily infested over a long period (females can lay 300 to 500 eggs). Like aphids, mealy bugs suck plant sap causing the plant to secrete honeydew, on which fungi or black moulds can easily grow. Root mealy bugs damage the roots. There are a large number of different types that are frequently specific to the host. Despite being insects, they don't look like insects, just a shapeless piece of cotton wool that are very difficult to attack because of their white, powdery, wax-like, water repellant hairs. Powder and liquid insecticides sit on the hairs and don't get the insect inside.