EUROPEAN PINE SAWFLY ( Neodiprion sertifer )
The European pine sawfly larvae, have black heads and grayish-green bodies. Each has a straight, off-white stripe down the middle of the back and slightly lighter stripes on either side. The larvae are gregarious, usually found in colonies of 10-100 larvae and are common in Scots, red, or Austrian pine plantations. They are rarely serious enough to warrant chemical control unless affected trees are within three years of harvest and a large population of sawfly larvae is present.
Eggs appear as yellow spots running the length of one or more needles, and they may easily be overlooked. Look for the young, newly hatched larvae instead when the eggs hatch in the spring in late-April to mid-May, and continue to monitor trees through August as many species have two generations per year. Larvae of the European pine sawfly may feed in colonies of up to 100 or more. They range from 1/4 to 2 inches in length depending on their age. Look, in particular, for straw-like needle remnants which the larvae have left behind in their feeding. These may be more visible against the green background of the tree than the greenish larvae.
Fig. 1. Eggs of the European pine sawfly embedded in Scots pine needles
When these larvae are found, they can often be eliminated by squashing the colonies with a gloved hand. Remove Scots pine that have grown beyond marketable size as they may serve as reservoirs for sawflies. Some chemicals are registered for use against sawflies where the population is very high and widespread. Treat only those trees where sawfly larvae are actually found, focusing spray directly on the colonies. Populations are usually so clustered that little is to be gained by preventative spraying of trees where no larvae occur. Northern strains of Scots pine, those from Northern Europe and Asia are believed to be more resistant to the European pine sawfly than those from more southerly locales.
Fig. 2. Larvae of the European pine sawfly
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