Spruce Galls

Table of Contents

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

Eastern Spruce Gall Adelgid, Adelges abietis

Symptoms:

Pineapple shaped galls found at the base of shoots of the current season's growth are caused by the sucking feeding of the adults and nymphs. Often tips of branches are dead 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 exist and these overwinter at the base of the next year's buds. In early spring, about the time when the buds are swelling, these small, greyish "stem mothers" begin to mature, feeding on bud bases, causing the galls to begin to form (Figure 1). By closely examining the base of the buds, the greyish adults covered in waxy, hairy fibres may be observed. Eggs are laid and nymphs emerge about ten days later and begin feeding on the new needles. Eventually the nymphs move to feed at the base of the needles. Continued feeding causes a gall to develop (Figure 2). This gall will enclose the nymphs.

By late July or early August the galls have dried and adults emerge (Figure 3). After laying eggs on suitable host plants, adults adelgids die. These eggs hatch and newly emerged nymphs overwinter at the base of dormant buds.

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Cooley Spruce Gall Adelgid, Adelges cooleyi

Symptoms:

The feeding of this adelgid results in susceptible spruces developing elongated galls which distort the tips of new shoot growth (Figure 4). Adults and nymphs suck plant juices resulting in the formation of galls. These galls often resemble "cones". On Douglas fir, injury appears on needles as yellowing or a distortion of growth and needles drop may occur. No galls are formed (Figure 5).

Hosts:

Colorado spruce, P. pungens and its selections; 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 spruce and on Douglas fir. Its life cycle is similar to that of the eastern spruce gall adelgid. 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 overwintering females hide on the underside of needles and lay eggs just prior to bud break. Feeding of the nymphs does not produce gall but rather results in the discoloration and distortion of needle growth.

Controls:

Galls removed and destroyed prior to them splitting open and adult emergence may provide some control for small infestations. Conventional chemical controls must be aimed at the overwintering nymph stage either in the early spring, about May 1 or when Magnolia x soulangiana is pink in bud but before petals have opened and spruce buds have begun to swell. A second treatment should follow about two weeks later. Treating in the fall during October may give some control of the nymphs before winter. When adelgids are in the egg stage or enclosed in the galls they are immune to chemical controls.

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

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.

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