Spruce Sawfly

Identification

Size: Adults typically measure around 7 to 8 millimetres in length.

Color: Spruce sawfly adults are generally black or dark brown.

Description: The spruce sawfly (Pristiphora abietina) is a non-stinging wasp species, with adults measuring about 7-8mm and being dark brown or black. They lay their eggs on spruce trees, leading to green larvae, often with darker patterns or spots, that resemble caterpillars and feed on spruce needles. These larvae can grow up to 25mm and cause significant defoliation, especially harmful to young trees or seedlings.

The spruce sawfly (Pristiphora abietina) is a type of non-stinging wasp that is particularly known for its impact on spruce trees. Adult sawflies are dark brown or black, typically measuring about 7 to 8 millimetres in length. They lay their eggs on spruce trees, and the larvae, which are often mistaken for caterpillars, hatch and feed on the needles of these trees. The larvae are green, often with darker patterns or spots, and can grow up to 25 millimetres in length.

Native to Europe, the spruce sawfly is now found in various parts of the world. In North America, it has been reported in the northeastern United States and eastern Canada, where it infests both red and white spruce. It is also found in other countries like Japan. Damage from the sawfly can lead to significant defoliation, particularly harmful to young trees or seedlings, and severe infestations can even cause tree death.

Control of spruce sawfly populations typically involves a combination of monitoring, fostering natural predators, and the use of insecticides in severe cases. Birds, beetles, and parasitic wasps are among the natural predators that can help control sawfly populations. It’s crucial to regularly monitor spruce trees for signs of sawfly larvae, as early detection and intervention can prevent more extensive damage.

Identifying a spruce sawfly requires observation of its physical traits and the signs they leave on affected plants. Adult spruce sawflies are dark brown or black and resemble non-stinging wasps, albeit without a pinched waist. They typically measure about 7 to 8 millimetres in length. While adults are less frequently seen, their presence can be an indication of a potential infestation.

The most recognizable and destructive stage of the spruce sawfly’s lifecycle is the larval stage. The larvae look similar to caterpillars, with green bodies that can feature darker patterns or spots. They can grow up to 25 millimetres in length. The larvae feed on the needles of spruce trees, often starting at the tips and working their way toward the base. This feeding pattern results in noticeable defoliation, which is another key sign of a spruce sawfly infestation.

Needle Damage: Spruce sawfly larvae feed on the needles of spruce trees. Look for signs of needle defoliation, especially from the tips toward the base of the tree. This can result in patches of bare branches or partially chewed needles.
Caterpillar-like Larvae: Spruce sawfly larvae resemble caterpillars and can be observed crawling on the tree’s branches and needles. They are green in colour and may have darker patterns or spots on their bodies.]
Silken Cocoons: After the larvae have finished feeding, they may spin silken cocoons on the tree’s branches or in the surrounding area. These cocoons serve as protective coverings during their pupal stage.
Presence of Adult Sawflies: Although less frequently seen than the larvae, adult spruce sawflies may be present near the infested trees. They are dark brown or black and resemble non-stinging wasps.

If you notice these signs, it is likely that you have a spruce sawfly infestation and should take appropriate measures to control their population and minimize damage to the trees.

Preventing spruce sawfly infestations involves several proactive measures that can help protect your spruce trees. Here are some prevention strategies:

Regular Inspection: Regularly inspect your spruce trees for signs of sawfly activity, such as defoliation or the presence of larvae. Early detection allows for prompt intervention.
Encourage Natural Predators: Foster the presence of natural predators of spruce sawflies, such as birds, beetles, and parasitic wasps, by providing habitat and food sources. These predators can help keep sawfly populations in check.
Prune and Dispose: If you spot any signs of spruce sawfly infestation, promptly prune and dispose of affected branches or twigs. This can help prevent the spread of the larvae to other parts of the tree.
Maintain Tree Health: Keeping your spruce trees healthy is key to preventing infestations. Ensure proper watering, regular fertilization, and overall tree care practices to promote tree vigour.

By implementing these preventive measures, you can reduce the likelihood of spruce sawfly infestations and minimize the damage caused to your spruce trees.