Zimmerman Pine Moth

"What's causing the holes in my pine trees?" is a common question at the Garden Shop. The answer depends upon where the holes are on the tree.

It could be a bird
If they are located on the trunk between branch whorls, Sapsuckers are probably the culprit. These woodpecker-like birds first drill evenly spaced horizontal holes around the trunk. When the holes result in strong sap flow they then make vertical holes to take advantage of the flow. They, and other birds, drink the sap and feed off any hapless insects caught in the sap. The damage to the tree is minimal and there isn't anything you could do about it anyway.

Or it could be a real pest
But if the holes are where the branches meet the trunk and there is also a hardened, crusty, whitish substance, it's an entirely different matter: the Zimmerman pine moth.

The larvae of this moth is the most serious insect pest of Austrian and Scotch pine in our area. Damage is most obvious on trees 10 to 15 years old or those stressed by drought or poor growing conditions.

Zimmerman pine moth over-winters in the larval stage and begins feeding in the spring, first on the bark, later tunneling into the cambium area of new growth on the branches.

Infested terminals become “fish-hooked,” turn yellowish-green, then brown. Toward the end of June, the larvae leave the new growth and tunnel in the whorl area where they girdle the branches and leaders, producing a whitish pitch mass mixed with sawdust.

The larvae pupate, emerge as adults in late summer, mate and deposit eggs in bark crevices, near wounds or on terminal buds. The eggs hatch in 10 days and the new generation immediately spin hibernating cocoons.

Too many years of repeated attacks can eventually kill your pine.

Timing is critical
Only newly hatched or immature larvae are vulnerable to chemical control. We recommend Ferti-lome Ornamental & Evergreen Spray. Only one application a year is needed and you have two windows of opportunity.

In the spring
Spray the entire tree when the larvae are moving from their over-wintering positions. This migration occurs when common Saucer Magnolias are in the pink bud or early bloom stage. If there are no Magnolias in your neighborhood look around for Soft or Silver Maples and spray when the new leaves are 1-2" long. Another indicator plant is Serviceberry, also known as Shadblow and Amelanchier. It will be in full bloom when it's time to spray.

In the late summer
Newly hatched larvae are vulnerable when Pee Gee Hydrangea, Hydrangea paniculata 'Grandiflora', is in pink bloom. Other indicator plants to watch for are two common roadside weeds: Goldenrod, in bloom and Queen Anne's Lace, when it's just about finished flowering and you can see some brown seed heads.