Evergreen trees in your home landscape look sturdy but are highly susceptible to infestation by mites. While spider mites infest a wide variety of trees, particular species are prevalent among different types of evergreen trees. To prevent this common problem of the home garden, familiarize yourself with what to watch for and effective control methods.
While the twospotted spider mite attacks the widest variety of home garden plants, evergreens act as host plants to particular species of mites other than the twospotted spider mite, according to the Colorado State University Extension. Honeylocust spider mites (Platytetranychus multidigituli), as their name suggests, feed on honeylocust trees. The spruce spider mite species Oligonychus subnudus looks for pine hosts. On spruce and juniper trees, spruce spider mite species Oligonychus ununguis also infests.
During the growing season, spider mites typically lay their eggs on foliage. After eggs hatch during the warmer months, mites may reach maturity within as short a time as a week; the entire reproductive and life cycle of the spider mite is a short one, resulting in the potential for quick population growth on evergreens. Spider mites can feed in any moisture content, but they thrive in arid environments, according to the Colorado State University Extension.
Symptoms and Damage
Spider mites on evergreen trees produce an easy-to-spot web that resembles what a true spider spins. This is a red flag symptom that your tree is infested, but the webbing doubles as a barrier to protect eggs, according to the Colorado State University Extension. Once an infestation takes hold, evergreen needles appear gray or as though burned by fire; this abnormal coloring is followed by defoliation. Spider mites are sucking bugs that feed on sap from plant tissue. Injury gives affected tree areas a dotted appearance. Your evergreen trees may end up in severe decline or may face death, particularly if the infestation is left untreated.
For natural control of mites on evergreens, release predatory mites into your garden. Predatory mites are bugs that hunt and kill spider mites without damaging your evergreens. One type of lady beetle (Stethorus species) known for its devastation of spider mites makes an effective natural control. Find predatory mites in garden supply catalogs or stores. Additionally, a strong stream of water pushes mites from needle surfaces and removes webs, according to the Colorado State University Extension.
Chemical control of spider mites on evergreens includes the application of pesticides. Apply a chemical with the active ingredient bifenthrin, sulfur of acephate, or apply insecticidal soap or horticultural oil, according to the Colorado State University Extension. Verify that the pesticide you purchase is formulated for use on the tree you are treating. When in need of assistance, contact your local county extension agent.