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 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.

Adelgid nymph within protective cottony wax feeding on Douglas-fir needle. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

Control by pruning out galls when seen; place sticky traps out in late summer (Douglas-fir or spruce) (1850-1950 GDD) to determine the timing to spray adults with insecticidal soap (+ sticker). Some of the tip “pineapple” galls on spruce have already opened up, and the winged adults have 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 Christmas Tree Pest Notes Blog for July 2023 also contains a few additional insect pests. Those included below are pine needle scale, pitch mass borer, white pine weevil, & some comments regarding cicada killer wasp predators.

[Read more…]

Armored scales are generally regarded by green industry plant managers as being one of the more difficult insect pests to control. The Cryptomeria scale (Aspidiotus cryptomeriae ‘Kuwana’) is an armored scale that is notorious for being especially difficult to detect because of the translucent waxy cover. The elongate hemlock scale species resembles this scale, but it has a waxy cover that is caramel brown in color. Although the hosts of Cryptomeria scale can potentially include numerous conifer species, they are most typically found on hemlocks & pines in the landscape and on true firs in production situations such as Christmas tree farms. The damage potential is especially high on true firs.

Signs of Cryptomeria scales beneath needles. (Photo: Steven K. Rettke, Rutgers Coop. Ext.)

Chlorotic banding & mottling symptoms produced by Cryptomeria scales on Fraser fir (Photo: Steven K. Rettke, Rutgers Coop. Ext.)

[Read more…]