Cottonwood sawfly, Nematus currani

Fig. 312   Cottonwood sawfly larva on leaf.	Fig. 313  Hybrid poplars defoliated by cottonwood sawfly.

Distribution:  Islands in the Fraser River near Chilliwack.  It has also been collected in the Cariboo and Kamloops Forest Regions.

TREE SPECIES ATTACKED:   Black cottonwood and hybrid poplars are susceptible.

WHAT TO LOOK FOR: Greenish-yellow sawfly larvae with yellow heads feeding on developing leaves early in the season.

INSECT DESCRIPTION & DAMAGE SYMPTOMS: Larvae are about 1.0 cm long, cylindrical, hairless, and uniform in diameter except for the tapered rear end. They have a yellowish head and a greenish yellow body with no distinct markings. Adults are 0.6 to 0.7 cm long. They have a black body with orange blotches on the back of the head, posterior to the eyes. Legs are yellow with black femurs. Adults emerge very early in the spring. Larvae feed on developing leaves, and feeding is usually completed by May. The larvae spin a cocoon in which they overwinter. There is one generation per year.

DAMAGE: Damage has only been reported on black cottonwood and hybrid poplars in the Chilliwack area. Defoliated trees generally refoliate by mid-summer. Several years of moderate to severe defoliation can cause reduction in radial growth and increased susceptibility of trees to root rots and other diseases.

SIMILAR DAMAGE: This insect will generally consume the entire leaf tissue, except the largest veins. Leaves damaged by leaf beetles will have untouched veins.

Back to the Pest Field Guide Index

Contact Tim Ebata if you have comments on the presentation of this information.

BC Ministry of Forests
Forest Practices Branch
P.O. Box 9513 Stn. Prov. Gov.
Victoria, BC
V8W 9C2

Section phone: (250) 387-8739
Section fax: (250) 387-2136

Last updated March 04, 2002