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Cooley Spruce Gall Adelgid (1850-1950 GDD = galls open): Colorado spruce (especially green forms), Sitka and Oriental spruce, and Douglas-fir share this pest’s two host life cycles. Mature adult females lay eggs at the tips of branches. These eggs hatch and the immatures move to new growth and start feeding. The combined feeding and salivary secretions induce the development of a bright green, oval “pineapple” gall on the terminals (as opposed to galls at the base of new growth on Norway spruce from the Eastern spruce gall adelgids). By midsummer, the gall will turn brown and crack open, as the adelgids within mature and emerge as adults. These winged adults migrate to Douglas-fir (or another spruce) and spend the remainder of the summer feeding on the needles, covered with cottony wax.

During late July or early August the adult Cooley spruce gall adelgids will emerge from the opened brown pineapple shaped galls. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

Sometimes Douglas-fir is so heavily attacked that needles are spotted, bent, or distorted. Two or more generations can occur on Douglas-fir through the following season (Christmas tree growers will treat Douglas fir when new growth is 3-4 inches). By next fall another winged generation flies back to spruce and lays eggs for the cycle to repeat itself.

After the Cooley spruce gall adelgid winged adults emerge from the “pineapple” galls on spruce some will relocate & infest Douglas-fir needles. They will remain on this host for the remainder of the summer. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

Control by pruning out galls when seen before they open in mid-summer. Place sticky traps out in  summer (Douglas-fir or spruce) (1850-1950 GDD) to determine the timing to spray adults with insecticidal soap (+ sticker). In southern NJ some of the tip “pineapple” galls on spruce will soon open up, and the winged adults will emerged. Except to improve the aesthetic appearance of the trees, there is nothing to be gained by picking off the galls after they have opened. Future control windows will occur during the fall or early spring months, against the overwintering females located at the bases of terminal buds. Some possible treatments include horticultural oil, carbaryl (Sevin), insecticidal soap, or imidacloprid (Merit).

The Landscape Pest Notes for July 2023 contains only insect/mite pests & a couple of predators commonly seen during the month. Contained below are 16 additional pests or predators that appear in the order they are listed as follows: Pine needle scale, Fall webworm, Obscure scale, Pitch mass borer, Two banded Japanese weevil, Aphids, Cicada killer, Juniper webworm, Sapsucker, White pine weevil, Peach tree borer, White waxy lady beetle, Japanese beetle, Oriental beetle, Dogwood sawfly, & Plant leaf galls. [Read more…]

Boxwood Spider Mite: (GDD =450-700) (PPI = Kousa Dogwood; Cranberry Bush) This spider mite, which attacks all boxwoods, is neither a true cool nor warm season mite species. It is usually most active with intermediate temperatures during late spring & early summer. The adult is yellow-tan in color with long legs. When the boxwood mites are active, they can be found on both the top & bottom of new growth. Eggs are light yellow & overwinter on leaves & twigs. There are several generations per year.

Boxwood spider mite feeding damage results in foliage with yellow to bronze stippling, which may resemble injury caused by thrips. Both of these insects cause distinctive linear stippling streaks. These symptoms can be diagnostic when observed on foliage. With high mite populations, entire leaves may develop yellowish-white streaks; premature defoliation can occur.

Boxwood spider mite feeding symptoms. This mite species creates linear streaks on leaves. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

Boxwood spider mite symptoms that are more mild. The distinctive linear streaks are more clearly observed. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

Detected overwintering eggs are treated with dormant oils (2-3%). Although normally unnecessary, summer oils (1-2%) or insecticidal soaps are recommended to control mild mite populations. With high infestations, some reduced-risk materials include spinosad, spiromesifen, acequinocyl, & bifenazate. Examples of other materials include hexythiazoc, abamectin, fluvalinate & acephate. Be aware that fluvalinate is a pyrethroid & can promote spider mite resurgence. Acephate may only provide mite suppression.

The Rutgers Plant & Pest Advisory Blog for Early June 2023 includes some commonly observed insect/mite & disease pests within the landscape during the late weeks of spring & early weeks of summer. In addition to boxwood spider mites, the other insect/mite pests included are juniper scale, bagworm, black vine weevil, bronze birch borer, pear leaf blister mite, & beneficial predacious mite. The disease pathogens included are fire blight, oak leaf blister fungus, black spot of rose, powdery mildew & Verticillium wilt. Some suggested monitoring techniques & variables are listed between the insect/mite & disease pests.     

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