Landscape and Nursery - Mites Present Now

The following are two mite pests to look for in the landscape and nurseries now and in the next 2 weeks. Information is from the University of Maryland.

Spruce Spider Mite, Oligonychus ununguis

Spruce Spider Mite. Photo by Petr Kapitola, State Phytosanitary Administration, Bugwood.org

Spruce spider mite hatches at about 30 - 50 degree days. We have reached this point in most of Delaware at this time.

Host: Look for spruce spider mites on junipers, spruce, arborvitae, cryptomeria, dawn redwood, hemlock, and pine.

Monitoring: Examine twigs for red eggs, usually near the base of the needles. The nymphs that are hatching are light colored. You can place a clipboard with white paper under the tree branches, rap the branches several times, and examine what’s crawling on the paper using a 10 -15 X magnification lens.

Control: Horticultural oil works very well on this mite. The mite growth regulators Hexygon and TetraSan work well when applied to young populations of mites. Avid, Floramite and Acari are some other options.

Boxwood Spider Mite, Eurytetranychus buxi

Boxwood Spider Mite. Photo from Rayanne Lehman, Pennsylvania Department of Agriculture, Bugwood.org

Boxwood spider mite overwinters as eggs and should be hatching in early April in most of Delaware. They have multiple generations per year but they become less active as we move into the hot part of the summer.

Hosts: English and European boxwood

Host resistance: Japanese and Korean boxwood tend to be less susceptible to boxwood mite

Monitoring: Use the clipboard/rap test for this mite. The mites will be tan colored with relatively long legs.

Control: Avid, Hexygon, horticultural oil, insecticidal soap

Information modified from the March 28 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers, University of Maryland Cooperative Extension. http://ipmnet.umd.edu/08Mar28L.pdf