Sawflies

Eric Bak, MAEAP Technician

As the days get shorter and the nights get a little cooler, many people are starting to notice the presence of different insects invading trees and smaller plants.  Recently, in Clinton County, sawflies are an insect of concern.

Sawflies are in the same order as bees, wasps and ants. The eggs hatch into small caterpillars that feed on plants in several different ways depending on the species.  The larvae are typically herbivores and feed on the foliage of trees and shrubs.  Sometimes they are leaf miners, stem borers or gall makers.  The name sawfly comes from the appendage that protrudes from the abdomen of the female which is used to cut into plants where they lay their eggs.

A light infestation may cause only a little aesthetic damage that can be easily removed through pruning or, when possible, by hand.  In large numbers, the sawflies can seriously damage or even kill a tree.

The best time to control sawfly is when you first notice the larvae infesting the tree or plant.  The natural insecticide spinosad, a bacterium, will control sawfly larvae.  The insecticide malathion is also an effective control.   Bt (Bacillus thuringensis), which is an effective natural control for true caterpillars is not an effective control for sawfly larvae.  It is also a good practice to make sure the plants are properly watered and fertilized, to keep them from becoming stressed.

Thanks to local residents David Main for the great photos (even though we are sorry to see the damage to your poor pine!) 

For more information on sawflies:

https://hortnews.extension.iastate.edu/sawflies

https://hort.extension.wisc.edu/articles/roseslug-sawfly/

https://www.wyevalegardencentres.co.uk/tips-and-advice_how-to-control-sawflies