Red pine sawfly

Systematic position. The red pine sawfly Neodiprion nanulus is a member of the order Hymenoptera and the family Diprionidae (conifer sawflies). It is a well-known forest pest characterized by its specific feeding habits on the needles of various pine species in North America.

Host plants. The insect primarily attacks various pine species, with a strong preference for red pine (Pinus resinosa), jack pine (Pinus banksiana), and eastern white pine (Pinus strobus). Its ability to infest both young plantations and mature stands makes it a significant forestry pest.

Biology and lifecycle. The sawfly typically completes one generation per year. Females deposit eggs into slits cut into pine needles in late summer or autumn. The insect overwinters in the egg stage. Larvae emerge in the following spring and feed gregariously, meaning they stay together in colonies, which significantly increases the damage impact per branch.

Damage characteristics and economic impact. Larvae feed primarily on old foliage during the early stages, moving to current-year needles as they grow. This intensive defoliation causes the foliage to wither and drop, leading to significant growth reduction. Severe infestations can kill small trees or weaken them to the point where they become susceptible to secondary bark beetle attacks.

Management and control. Integrated Pest Management (IPM) is essential for controlling this pest:

• Monitoring egg clusters in late autumn or early spring to predict infestation levels.
• Biological control using virus-based insecticides or beneficial predators and parasitoids.
• Chemical intervention using registered insecticides specifically during the early larval stages when they are most vulnerable.
• Silvicultural practices, such as thinning stands to increase tree vigor and reduce the likelihood of heavy outbreaks.