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April 14, 1999
Spruce spider mites and related mites that feed on spruce, pine, arborvitae, juniper, and other needled evergreens are active in early spring. Check for infestations by firmly striking a branch. The mites will drop onto a piece of white paper held below the branch, and the tiny greenish mites will then be easily seen. Reddish mites that are found are likely to be predatory mites that are eating the pest mites. Control spruce spider mites with two or three weekly sprays of dicofol (Kelthane), insecticidal soap, bifenthrin (Talstar) or dimethoate (Cygon) according to the label.

Zimmerman pine moth can be controlled at this time of year with a spray of chlorpyrifos (Dursban) or dimethoate (Cygon). The caterpillars wander around on the bark surface in the spring where they are susceptible to insecticides.

Ash plant bug can also be controlled at this time of year with applications of acephate (Orthene), bifenthrin (Talstar), cyfluthrin (Tempo), and insecticidal soap.

Eastern tent caterpillar will be hatching as leaves come out on crabapples, hawthorns, mountain ash, and other related trees. Look for 1- to 2-inch-wide silk tents in twig crotches. These tents can be pruned out or removed by hand at night or only on cloudy or rainy days when all of the caterpillars will be in the webbing. If sprays are needed, Bacillus thuringiensis kurstaki is recommended to avoid killing bees coming to the blooms of flowering trees.

Juniper webworm activity is being reported by The Morton Arboretum. Brownish masses of foliage should be inspected closely for silk webbing and caterpillars. Bacillus thuringiensis kurstaki and other chemical insecticides are effective at this time in preventing more severe damage later in the spring. (Phil Nixon and The Morton Arboretum)

Author: Phil Nixon staff at The Morton Arboretum


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