Redheaded pine sawfly

Redheaded pine sawfly - Larval colony on a Scots pine shoot
  • Latin name: Neodiprion lecontei (Fitch)
  • French name: Diprion de LeConte
  • Order: Hymenoptera
  • Family: Diprionidae
Description

Distribution

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

Micro-habitat(s)

Needle

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)

Life cycle (East of the Rockies)
Stage/Month J F M A M J J A S O N D
Egg
 
Larva
 
Cocoon
 
Adult
 

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.

Canadian Forest Service Publications

Redheaded pine sawfly

Diet and feeding behaviour

  • Phyllophagous : Feeds on the leaves of plants.
    • Free-living defoliator: Feeds on and moves about freely on foliage.
Information on host(s)

Main host(s)

Jack pine, red pine, scots pine

Photos
  • Redheaded pine sawfly Lateral and dorsal views of two mature larvae
  • Redheaded pine sawfly Female and male cocoons (lengths: 10.3 and 7.5 mm)
  • Redheaded pine sawfly Mating (female length: 6-9.5 mm, male length: 5-6.5 mm
  • Redheaded pine sawfly Larval colony on a Scots pine shoot
  • Redheaded pine sawfly Larval colony on a Scots pine shoot
  • Redheaded pine sawfly Plantation of young red pines killed by the insect
  • Redheaded pine sawfly Arrangement of eggs on pine needles
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