The fir coneworm , Dioryctria abietivorella is found through most of North America. Coneworm belong to the Pyralidae family better know as snout nosed moths. Their larvae feed on a variety of conifers including Douglas fir, balsam fir, grand fir, subalpine fir, jack pine, spruces, pines, larches, and hemlocks. Fir coneworm were first recorded in Canada in 1939 and outbreaks occur as local infestations within Ontario and Quebec. These local infestations usually occur at tree nurseries, plantations and cone-seed orchards.

Life Cycle

In Canada, the fir coneworm typically have only one generation per year but development is not well synchronized and larvae are found in cones from spring to fall. Fir coneworm overwinter as a late instar larva or pre-pupa within cocoons normally found on the ground. In the spring they moult into pupae, which are amber to reddish-brown in colour and about 11.0 mm long. Adults emerge a few weeks later as grey moths with distinctive black and white transverse “w” shaped bands located at the midpoint and tip on their narrow forewings. Their hindwings are a greyish-white with a narrow dark grey band bordering the perimeter. During the summer months, adults mate and females lay whitish-green oval eggs 1.0mm long, near cones. As egg mature and get closer to hatching, they turn orange-red in colour. When larvae first hatch, they have yellow-amber bodies with brown heads. As they mature, their bodies turn darker brown with rows of brown spots and are extremely active when disturbed.

Damage and Nuisance

Fir coneworm larvae prefer to feed within cones on seeds and scales but will also feed on terminal shoots, bark, branches and twigs. Larvae also have the capability of mining into tree trunks and branches. Signs of damage include ragged holes on the outside of cones surrounded with small amounts of frass and resinous material, mined terminal shoots, new cones stuck together with webbing and chewed needles or pitch masses at entry points on branches and trunks of trees. Fir coneworm typically do not damage trees but can pose a threat to seed and cone crops in seed orchards.

What can I do?

For private landowners, controlling fir coneworm may prove difficult. The greatest problem is getting to the larvae because they stay hidden so well within cones, branches and feeding shelters. If there are small trees, few in number, manually removing and burning cones while larvae are still within them ( i.e., before September) may prove effective. Removing the top duff layer surrounding infested trees in autumn may prove effective by exposing over-wintering larvae to predation and eliminating this protection may also subject the larvae to harsher (freezing) environmental conditions, thus reducing survival over the winter.

Contact

John Dedes, Insectarium Supervisor
Canadian Forest Service, Great Lakes Forestry Centre
1219 Queen Street East
Sault Ste. Marie, ON P6A 2E5
(705) 541-5673
jdedes@nrcan.gc.ca

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