Sawfly on Evergreens

Caterpillar-like, sawfly larvae are common springtime pests. SJuniper sawflyeveral species feed on the old needles of evergreen trees in groups and can cause extensive defoliation in some years. The adult sawfly is a stingless wasp that causes no harm.

Larvae typically feed for two to three weeks, primarily in early May. Sawfly larvae also may be Web-spinning sawfly in sprucefound on Ponderosa pine in March, and on other pines later in the summer. Gardeners often observe feeding damage after the larvae have gone and the damage is done for the year.

Light populations may not cause serious damage, but moderate to heavy populations can significantly impact tree health. When sawfly larvae are present in high numbers, sprays are justified to protect tree health.Sawfly, Neodiprion ventralis, larvae feeding on needles

To control sawfly larvae, spray infested evergreens with insecticides such as Orthene (acephate), permethrin or bifenthrin. Even though the larvae are caterpillar-like, the natural insecticide Bt, or Bacillus thuringiensis, isn't effective because they are not true caterpillars.Mating pair of juniper sawfly

Apply insecticidesearly, while sawfly larvae are young. Complete coverage is important for control. Spray ONLY the infested trees, but occasionally examine other trees for possible Bull pine sawfly, Zadiprion townsendi, larvaeadditional outbreaks. Sawflies are more prone to attack single landscape trees that are planted out in the open, rather than trees in a forest-like setting.

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Updated Thursday, October 16, 2014