Redheaded pine sawfly

Distribution

Quebec, New Brunswick, Nova Scotia, Ontario, Prince Edward Island

Micro-habitat(s)

Needle, Twig

Damage, symptoms and biology

Red-headed pine sawfly damage is observed primarily in pine plantations and on trees less than 3 m tall in natural forests. Depending on the severity of the attack, the consequences of defoliation may range from growth reduction to the mortality of affected trees.

An infestation of this species can be suspected if colonies of pale yellow larvae bearing black dorsal spots are found on trees between July and September. The larvae feed primarily on the previous year's foliage, but during heavy infestations, they may also attack new needles and even the tender bark of twigs.

In addition, clusters of eggs may be observed on the needles as early as June. Other signs pointing to red-headed pine sawfly attacks are the absence of old foliage, the presence of dead young pines near healthy pines and reddish-brown cocoons on the ground at the base of trees.

In July, the young larvae feed on the outer portion of the needles, leaving only a thin filament. Later on, older larvae devour the entire needle. At the end of summer, the larvae drop to the ground and spin a cocoon in which they overwinter. Pupation does not occur until spring, and a portion of the population may remain in diapause for more than a year.

Life cycle (East of the Rockies)

Other information

Although the red-headed pine sawfly, which is native to North America, has been widely known since 1859, it did not attract much attention until the 1920s. Collected each year in Canada, the insect produces severe localized infestations lasting roughly three to four years and occurring at fairly close intervals.

Climatic conditions, numerous parasitoids and entomopathogenic micro-organisms have helped to reduce populations of the red-headed pine sawfly. Experimental testing of a virus, carried out in Quebec and Ontario in 1970, confirmed its efficacy against the sawfly.

For ornamental or isolated trees, the recommended approach is to shake the stems and collect and destroy all the larvae that fall to the ground.

Main host(s)

Jack pine, red pine, scots pine