Spruce Coneworm: Appearance, Territory, Damage and Life Cycle

Latin Name: Dioryctria Reniculelloides

Appearances: Coneworms are mottled grey snout moths with minor colour bands as adults. Coneworm larvae are small, cream-colored or light brown in tone with a dark head. Coneworms are mottled grey snout moths with minor colour bands as adults. Coneworm larvae are small, cream-colored or light brown in tone with a dark head.

Host Plants: Balsam fir, black spruce, red spruce, and white spruce are the main hosts.

Territory: They are mostly found in Canada.

Damage Caused: On cones, holes and frass bound together by webbing are telltale evidence of the insect. Activity is also indicated by reddened needles and frass mixed with webbing between the needles near the buds. The larvae prefer to eat cones, but if cones are rare, they will eat leaves. Before moving on to the buds or cones in the spring, the juvenile larvae will mine one or two old needles. Pollen from male flowers, particularly white spruce, is also consumed by the insect on occasion. When phyllophagous larvae (such as the spruce budworm) compete for food with it, such as when foliage is limited, this coneworm may feed on them.

Cones can be entirely destroyed at times. Defoliation causes the tree to lose its ability to develop, weaken it, and make it more vulnerable to insect attacks.

Life Cycle and Habits: Each year, the spruce Coneworm produces one generation. The adults lay their eggs in the crown of the tree shortly after they emerge. The larvae bore into the cones as the eggs hatch, where they completed part of their development before entering diapause for the winter. The juvenile larvae may overwinter in a silk shelter and bore into the cone the following spring if laying happens late in the season.

In their life cycle, all coneworm species go through four stages: eggs, larvae (caterpillar), pupae (cocoon), and adults. Adult moths are tiny and go unnoticed most of the time.

Coneworms prey on the fragile bark tissues of genuine firs by burrowing into shoot tips or stems, especially around wounds. The part of the branch that isn’t harmed may die back. Coneworms can also dig into green cones, feed on the fragile bark of new growth, or feed on the trunk cambium inside the bark. Other insects that attack cones and many small moths that tunnel into shoots further complicate the situation.