Your Guide

Hosts: Blue, Engelmann, Norway spruces, and Douglas Fir.

Identification: Adelgids, formerly known as aphids, are gall insects. On spruces, they cause pineapple-shaped galls at the twig tips. While Douglas firs don’t produce galls, they can show signs of infestation such as yellowed, distorted needles, and wooly adelgid bodies.

Life Cycle: Adelgids have two generations per year and can live on one or two hosts. They overwinter as nymphs, mature in April, and lay eggs that hatch into nymphs. They  feed at the needles’ bases, causing galls. By mid-summer, galls dry and open, allowing adelgids to spread.

Damage: Infestations can seriously disfigure spruces and reduce their aesthetic value. On Douglas firs, adelgids cause yellowed, crooked needles. 

Monitoring: Check for white, wooly adelgids under Douglas firs’ needles. On spruces, look for green (turning brown by mid-summer) pineapple-shaped galls. Inspect your spruces’ shoot tips for overwintering nymphs in mid-September.

CONTROL STRATEGIES:

Physical: For small spruces, remove galls by pruning in July before they open. Avoid planting Douglas firs near spruces to prevent cross-infestation.

Cultural: Do not fertilize infested trees; it encourages adelgid feeding. Some trees show natural resistance.

Chemical: Target overwintering nymphs on spruces’ twig tips. The best treatment times are in April (when buds break) or in mid-to-late September. Use insecticidal soap or horticultural oil on Douglas firs when adelgids are present in early May or from late July to early August.

Hosts: European White Birch, Paper Birch, Yellow Birch, and Poplar.

Identification: The bronze birch borer is a wood-boring beetle. The adult beetle is recognizable by its deep green-bronze colour, and is 1/4- to 1/2-inch long. A common way to spot the beginning of an infestation is with the appearance of D-shaped holes in your tree bark, starting in early June and lasting the whole month. Mature larvae are about one inch long, white, slender, and flat. The area behind their head is wider than the rest of their body. 

Life Cycle: The bronze birch borer has a two-year life cycle, with generations overlapping each year. Adults emerge in early June, feeding on leaves before laying eggs in bark crevices. Larvae hatch and tunnel into the cambium, residing in the sapwood for 1-2 years before maturing.

Damage: These pests primarily affect weakened and stressed trees, causing girdling which may lead to tree death. Early signs include sparse, yellow foliage, branch die-back, and sap bleeding from the trunk. 

Monitoring: Look for signs of stress in birches, such as bleeding trunks, dead branches, D-shaped exit holes, and a sparse canopy of yellow foliage. A birch being crowded by adjacent trees can also cause stress.

CONTROL STRATEGIES:

Physical: Tree removals can be recommended for severely affected trees to prevent further infestation.

Cultural: Maintain optimal growing conditions. White and paper birches thrive on the edges of wooden and open areas. Ensure birches are not outcompeted by adjacent trees, and avoid lawn treatments that may harm their shallow root systems. Also note that "Heritage" river birches and possibly monarch birches show resistance to these pests. 

Chemical: If the canopy is thin with significant dieback, target the adult beetles by spraying the foliage, branches and trunks with insecticide from June 3 to 24 (GDDs: 440-800).

Hosts: Norway Spruce, White Spruce, Blue Spruce, and Red Spruce

Identification: These Galls are smaller (1/2 to one inch long) and typically form at the bases of shoots. They can’t migrate to Douglas firs. 

Life Cycle: Females overwinter near the buds. The pest's life cycle is similar to the Cooley spruce gall adelgid. These galls form early in the season, with the winged form reinfesting spruces later in the year.

Damage: Infestation leads to weakened, distorted trees with brown, dying twigs. The presence of numerous galls diminishes the ornamental value of the trees. It also causes more damage than the Cooley spruce gall adelgid because it’s harder to eliminate with pruning.

Monitoring: Look for green or brown pineapple-shaped galls at shoot bases. Also check for overwintering adelgids in the bud base or shoot tips.

CONTROL STRATEGIES:

Physical: Avoid fertilizing infested trees to prevent stimulating adelgid feeding. 

Chemical: The optimal periods to treat this infestation are between April 2 and May 12 (GDDs: 22-170), as well as August and mid-september. These periods are perfect to target exposed nymphs and adults. We particularly recommend August because of the absence of an alternate host.

Hosts: Pines, Spruces, Douglas Firs

Identification: The adult beetles can be recognized with their orange and white markings. They’re also ¼ inch long. They overwinter in the ground and move to terminal shoots in early spring.

Life Cycle: There is one annual generation. Adults lay eggs in the leader, where legless, white grubs hatch, feed beneath the bark, and tunnel through the leader. Adults emerge from late June through August.

Damage: When larvae feed on the top shoot of a tree, they can cause it to droop, turn brown, and die, affecting the tree's growth over a period of 2-3 years. Although this doesn't usually kill the tree, it can cause the tree to grow unevenly or split into multiple parts at the top.

Monitoring: In April, look for resin flow from feeding holes on young trees' terminal leaders. Starting in June, watch for wilted, brown, or dead leaders.

CONTROL STRATEGIES:

Physical: Remove and destroy injured leaders by late June to eliminate larvae and pupae. This method has proven to be successful.

Chemical: If needed, spray tree tops, focusing on the terminal area, to control adults before they lay eggs. The optimal treatment period is mid-March to April 25 (GDDs: 7-58).