Fir coneworm

Larva into its galery of twig Thérèse Arcand

French common name: Pyrale des cônes du sapin
Scientific name: Dioryctria abietivorella (Grote)
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Pyralidae
Partial list of synonyms:
- Dioryctria abietella Grote

Distribution

Canada

Damage, symptoms and biology

Symptoms of an infestation include cones stuck together by frass mixed with webbing, chewed needles and mined terminal shoots.

Larvae prefer cones, but will also feed on the terminal shoots and the bark of the trunk and large limbs. Occasionally, the larvae will even mine the actual branches or trunk of the tree. On young pines, the species’ presence is revealed by a pitch mass near an entry point on the trunk. The fir coneworm does not cause serious damage to the tree, but in severe infestations, it may destroy an entire seed and cone crop. It is particularly damaging in seed orchards.

Towards the end of the larval stage, the caterpillar drops to the ground and weaves a silk cocoon where it overwinters during the last larval instar or as a prepupa, and pupates the following year. In eastern Canada, this species only has one generation per year. Larvae infest the cones beginning in mid-June and remain until fall.

Other information

Reported in Canada for the first time in 1939, the fir coneworm is similar in many respects to the spruce coneworm. Outbreaks have been limited to occasional local infestations in Ontario and Quebec. Most occurrences have been reported in plantations and seed orchards.

To reduce the larval population on ornamental trees, the cones should be collected and burned while the larvae are still inside (before mid-August).