Spider mites are small, eight-legged arthropods that attack many ornamental plants. Spider mites are a sap-sucking insect, meaning they remove sap from leaf tissue. Mites pierce the outer leaf surface with their sharp, slender mouthparts as they feed. When they extract the sap, the tissue of the leaf collapses in the area of the puncture. Soon a chlorotic (yellow) spot forms at each feeding site. After a heavy attack, an entire plant may become yellowed, bronzed, partially defoliated or completely killed. Spider mite outbreaks are more likely to occur during hot and dry conditions. Spider mites are not actually insects. More closely related to spiders than insects, they derive their name from the thin web that some mite species spin. Observe the plants for webbing between the leaf petiole, stems and leaf edges. Observe the plant for chlorotic discoloration, stippling, and eggs or cast skins on the underside of the leaf. A hand lens or other magnification is a useful aid for seeing mites on the foliage.

If a spider mite infestation is identified, spray the undersurfaces of leaves with miticide at five-day intervals until mite infestations are suppressed. Usually two to three applications are required. Do not use horticultural oil (various brand names) more than once per week. Some miticides can be used only once per year or need to be applied early in the season at specific growth stages of the host plant. Follow label directions. Do not apply any miticide to ornamental, vegetable or fruit plants that are not listed on the label.

For chemical control recommendations, consult the Insect and Plant Disease Control Manual, UT Extension Publication 1690, found here. Please contact your local Extension office for specific pesticide recommendations.