West Virginia University

Improve control with identification, timing, and pesticide selection. Although visible only as small bumps on leaves, twigs, and branches, scale insects are one of the most problematic pests in urban landscapes and nurseries. When outbreaks of scales occur, plants can lose their vigor, become unsightly, or even die. Heavy infestations of scales have multiple causes. Populations of these sap sucking insects can increase rapidly on plants whose sap becomes more nutrient rich from inappropriate fertilization, lack of water, and higher temperatures in urban landscapes. In addition, pesticide use can make the problem worse by killing the natural enemies that can help keep populations low. Here, we discuss an Integrated Pest Management (IPM) approach to use pesticides in ways that kill scale insects, but leave enough healthy beneficial insects to keep populations low. Scale Basics Like most true bugs, scale insects have sucking mouthparts. Closely related to aphids and mealybugs, scales feed on plant sap. Unlike aphids, they are only able to walk on plant tissue for a small part of their lives. Indeed, their habit of staying in the same spot through most of their lives have earned them the nickname: “barnacles” of the plant world. Female scales lack wings. Males only have wings as adults to help them fly to a female and mate. Eggs laid by females will hatch into flat, six-legged insects that crawl to find a suitable feeding spot to settle. Called crawlers, this is the life stage most easily killed by insecticides. Guides to identify ...