Spruce Bud Scale - Curtis Young


Spruce bud scale (Physokermes piceae) is an aptly named insect. The adult female scales can be found nestled behind the tree’s bud scales of previous seasons’ growth. The shape and color of these females is highly variable and changes as they mature. They are approximately 1/8” - 3/16” in diameter, globular and yellowish to dark brown in color. Fully matured females have a light dusting of white wax over their exposed surface. At a quick glance, they look like buds of the tree. There may be one to several aggregated behind the scales of a node.

Spruce bud scale is commonly found (if you know what you are looking for) on Norway spruce (Picea abies) but can be found on other spruces and according to some, occasionally on pine. As the females feed, they produce copious quantities of honeydew. The honeydew will collect in teardrops of clear, glistening liquid hanging from the exposed tip of the scale and eventually drip on objects below. Some will stick on the needles while the rest drop from the trees. The drips will speckle objects on the ground giving a hint that something is going on above. If the honeydew is not washed away by rainfall, sooty mold spores may land in it and germinate.

In NW Ohio, several populations have been recently found due to the honeydew accumulations. A lack of heavy rains for a week or more has allowed the honeydew to collect in the trees. It also helps that most of the females settle on the lower branches of the tree. On stressed trees, the feeding by the scale may be the cause of branch death.

These females may have been mated by males and developing eggs or they may not be mated and be parthenogenetically producing eggs. The females will eventually lay their eggs under their bodies. These eggs will hatch sometime between mid-June through late-July. The newly hatched nymphs (crawlers) are extremely small (3/64”) and yellow-orange in color. The crawlers move to needles where they settle to feed and develop to the second instar nymph. Second instar nymphs are also relatively small, flattened and oval to globose in shape. They are brownish yellow to dark brown in color. This is the stage that overwinters. In the spring, the overwintered second instar nymphs move to the bud scales at the bases of old growth. There, they settle in to finish their development. There is only one generation per year.

Management of this scale is not a high priority. Manage the health of mature landscape trees as much as is feasible with appropriate horticultural practices.

The spruce bud scale may need to be managed in Christmas tree plantations and nursery production fields. These trees should be monitored for scale infestations. If populations are discovered, apply a foliar insecticide treatment (carbamate; horticultural oil; insecticidal soap; organophosphate; pyrethroid) to coincide with scale crawler activity or apply a systemic neonicitinoid in the springtime after new needles have expanded.