Spruce Galls

 

This infosheet was originally written by Christoph Kessel, former Nursery Crops Specialist, OMAFRA. It has been updated by Jennifer Llewellyn, Nursery Crops Specialist, OMAFRA.

Table of Contents

  1. Eastern Spruce Gall Adelgid
  2. Cooley Spruce Gall Adelgid

Eastern Spruce Gall Adelgid, Adelges abietis

Symptoms:

Green, pineapple shaped galls found at the base of shoots of the current season's growth from spring to summer. In late summer, galls open and turn brown. Often the tips of infested branches are dead, especially if the plant is heavily infested.

Hosts:

Norway spruce, Picea abies; Colorado spruce, P. pungens; white spruce, P. glauca; red spruce, P. rubens.

Life Cycle:

Only females are known to exist. Nymphs overwinter on the undersides of leaf buds, at their base . Nymphs are small, aphid-like, bluish-grey and about 2-3 mm long. In early spring, about the time when the buds are swelling, these small, greyish nymphs (or "stem mothers") will feed on bud tissue and start to mature. As they mature, they cover themselves in white, waxy fibres. By closely examining the base of the buds in early spring, the greyish adults covered in white, waxy fibres may be observed (Figure 1). Eggs are laid and nymphs hatch about ten days later and begin feeding on the new needles. Eventually the nymphs move to feed at the base of the needles and feeding will cause a gall to develop (Figure 2). This gall will enclose the nymphs.

By late July or early August the galls will turn brown, small openings will appear and winged adults will emerge (Figure 3). After laying eggs on suitable host plants, adult adelgids die. These eggs hatch and newly emerged nymphs overwinter on the undersides of leaf buds, at the base.

Stem mothers on spruce

Figure 1: Stem mothers overwintering on spruce.

Pineapple-shaped galls form at the base of new growth as a result of the feeding from larvae.

Figure 2: Pineapple-shaped galls form at the base of new shoots as a result of the feeding from nymphs.

Galls dry to a brown colour in late summer. Chambers crack open to release winged adults.
Figure 3
: Galls turn brown in late summer. Small openings appear and winged adults will exit the gall.

(Photo credit: Dave Cheung, University of Guelph)

Cooley Spruce Gall Adelgid, Adelges cooleyi

Symptoms:

Green, C-shaped elongated galls will appear at the tips of new shoots from spring to summer (Figure 4). In late summer, galls turn brown and small openings will appear. On Douglas fir, this insect does not form a gall but feeds openly on needles. Feeding injury on Douglas fir appears as yellow, distorted needles (Figure 5) and nymphs are visible with white, waxy fibres as they mature.

Hosts:

Colorado spruce, P. pungens and its cultivars; Engelmann spruce, P. engelmannii; Douglas fir, Pseudotsuga menziesii.

Life Cycle:

This adelgid can complete its life cycle either on spruce or Douglas fir or live part of its life on each host. Its life cycle is similar to that of the eastern spruce gall adelgid.
On spruce, nymphs overwinter on the undersides of leaf buds, at their base . Nymphs are small, aphid-like, bluish-grey and about 2-3 mm long. In early spring, about the time when the buds are swelling, these small, greyish nymphs (or "stem mothers") will feed on bud tissue and start to mature. As they mature, they cover themselves in white, waxy fibres. By closely examining the base of the buds in early spring, the greyish adults covered in white, waxy fibres may be observed (similar to Figure 1). Stem mothers lay eggs and nymphs hatch about ten days later and begin feeding on the new needles. Eventually the nymphs move to feed at the base of the needles and feeding will cause a gall to develop (Figure 4). This gall will enclose the nymphs. Immature females, overwintering under bark scales near the dormant terminal buds, are small, grey and oval in shape. As the new growth begins, adults can be easily recognized by the masses of white, waxy, hairy fibres which they produce. Eggs are laid about the time as the bud cap splits. After hatching, emerged nymphs migrate to the newly developed shoots and begin to feed. Their feeding stimulates the spruce to develop galls, enclosing the nymphs. By July the galls open and adults emerge and fly to other host plants where eggs are laid and a subsequent overwintering generation is produced.

On Douglas fir, nymphs overwinter on the underside of leaf buds at their base. The nymphs will start to feed, mature and cover themselves with white, waxy fibres. Mature adelgids (or "stem mothers") lay eggs just prior to bud break. The next generation of nymphs will hatch about 10 days later. Nymphs will feed openly on needles and do not produce galls but cause needle yellowing and distortion of current season's needles (Figure 5).

Management:

Remove and destroy galls while they are still green and tightly closed, to prevent the emergence of the next generation of adult adelgids. Pesticide applications should be directed at the overwintering nymph stage (undersides of buds) in the early spring when Magnolia x soulangiana is pink in bud. This early spring application should take place before the spruce buds have begun to swell, before nymphs develop protective, white, waxy fibres around their bodies. Pest control applications in mid-Autumn may give some reduction of nymph populations before winter. When adelgids are in the egg stage or enclosed in the galls, they are immune to pest control applications.

The ends of new shoots curl and seal as a result of the feeding damage from larvae.

Figure 4: The ends of new shoots curl and seal as a result of the feeding damage from larvae.

Feeding damage on Douglas Fir does not cause galling, but chlorosis and twisting of new needles.

Figure 5: The alternate host of this adelgid is Douglas fir. Feeding damage on this host does not cause galling, but chlorosis and twisting of new needles.
(Photo credit: Dave Cheung, University of Guelph)

 


For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca
Author: Jennifer Llewellyn - Nursery Crops Specialist/OMAFRA
Creation Date: July 1999
Last Reviewed: 14 January 2010