Spruce coneworm

Dion Manastyrski Centre de foresterie du Pacifique, Victoria (Colombie-Britannique) / Pacific Forestry Centre, Victoria, British Columbia

French common name: Pyrale des cônes de l'épinette
Scientific name: Dioryctria reniculelloides Mutuura and Munroe
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Pyralidae
Partial list of synonyms:
- Dioryctria reniculella (Mutuura & Munroe)

Distribution

Canada

Damage, symptoms and biology

Telltale signs of the insect on cones include holes and frass held together by webbing. Reddened needles and frass mixed with webbing between the needles near the buds are also signs of activity.

The larvae mainly feed on cones, although they will turn to foliage when cones are scarce. In spring, the young larvae will mine one or two old needles before moving on to the buds or cones.

The insect also occasionally feeds on pollen from the male flowers, particularly on white spruce. This coneworm may also feed on phyllophagous larvae (such as the spruce budworm) when the latter are competing with it for food, particularly if foliage is scarce.

Cones are sometimes completely destroyed. Severe defoliation results in loss of growth, weakening of the tree and increased susceptibility to attacks by other insects.

The spruce coneworm has one generation per year. Shortly after emerging, the adults lay their eggs here and there in the crown of the tree. When the eggs hatch, the larvae bore into the cones, where they undergo part of their development before entering diapause for the winter. When laying occurs late in the season, the young larvae may overwinter in a silk shelter and bore into the cone the following spring.

Other information

The spruce coneworm is a native insect often associated with the spruce budworm. It was reported in Canada for the first time in 1937 and almost every year since. Populations usually increase during years of good cone crops.

To reduce the larval population on ornamental trees, the cones should be collected and burned while the larvae are still inside (i.e., in fall or winter).