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Sawflies

Quick facts 

  • Sawflies are related to wasps and bees.
  • They mostly attack trees and shrubs.
  • A common sawfly in Minnesota is found on columbine.
  • Larvae emerge in early spring and damage plants by eating leaves or needles. 
  • Adults typically emerge in the spring or early summer.
  • Sawfly damage affects the appearance of trees or shrubs but does not affect plant health.

How to identify sawflies

A black fly with clear wings on a leaf
Adult female sawfly

Adult sawflies are small, stout-bodied, non-stinging wasp-like insects.  They are rarely seen in the landscape. Their name comes from the saw-like egg-laying structure of adult females.

Difference between sawfly larvae and butterfly and moth caterpillars

Sawfly larvae are more commonly seen than adult flies. They look similar to butterfly and moth caterpillars. They differ from each other in the number of prolegs—the fleshy, leg-like projections on the abdomen.

Light green caterpillar with eight pairs of leg-like structures
Sawfly caterpillar
A green caterpillar with five pairs of leg-like structures
Caterpillars have fewer pairs of prolegs
  • Caterpillars have two to five pairs of prolegs on the abdomen.
  • Sawflies have six pairs of prolegs or more.
  • The prolegs on slug sawflies are small and barely visible.  
  • Sawfly larvae are smooth with little or no hair and are no more than one inch long when fully grown.  
  • Moth and butterfly caterpillars can be smooth, hairy or spiny, and vary in size when mature. They may often be larger than one inch long.

When sawflies feel threatened, they simultaneously raise and arch their bodies as a defense mechanism. 

How to protect your plants from sawflies

The treatment plan for sawflies depends on many factors:

  • Time of year 
  • Health of the plant
  • Conifer or deciduous tree or shrub
  • Number and size of sawfly larvae 
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Sawflies on coniferous trees and shrubs

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Sawflies on deciduous trees and shrubs

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Slug sawflies on deciduous trees and shrubs

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Sawflies on herbaceous plants

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Jeffrey Hahn, Extension entomologist and John Lloyd

Reviewed in 2018

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