If you have noticed a great number of pests in pines through the landscaping around your home or other space, around Christmas tree plantations or in ornamental nurseries, the pests are likely European pine sawflies or their larvae. According to TreeHelp.com, the European pine sawfly, Neodiprion sertifer (Geoffroy), is the most common sawfly found infesting pines in these areas. The larvae actually look more like caterpillars than the larvae of primitive wasp-like insects, so it’s easy to confuse the two. European sawflies and their larvae are found mostly in regions from southwestern Ontario through New England and west to Iowa. No one knows exactly how the pest made it’s way to the U.S. All that is known is the sawfly was accidentally introduced from Europe.
In addition to mugo and tabletop pines, the European sawfly attacks
Scotch, red, Jack, and Japanese pines. If you are nervous about protecting your Austrian, Ponderosa, shortleaf, white or pitch pines, don’t worry. The sawfly rarely attacks these types of trees.
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Unfortunately for the sawflies preferred host, the damage is can lead to defoliation or “bottle brush” appearance. What this means is, the old pine needles have all but disappeared, but the current years needles are still alive and well. Fortunately, even heavily infested trees will survive the attack. TreeHelp.com offers the following information about the feeding habits of the sawfly larvae. “The first instar larvae (the ones hatching from the egg) can only eat the needle surface which causes the needles to turn brown and wilt, appearing straw-like. As the larvae grow, they remain together and feed from the tip of a needle to the base. The larvae feed on older foliage and move from branch to branch as they strip the needles. Larvae will often migrate to new trees if the needles on their current host have been devoured.”
How to Control the European Sawfly Without Damaging Your Trees
There are a number of different methods to control the Europe sawfly and its larvae including natural controls, mechanical controls, and insecticides. It is important to note that with any method of control, it’s always a good idea to catch the larvae while they are very small. Perform inspections in late winter, April and May.
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Method 1: Natural Controls – Several parasites have been introduced to control this pest and native birds feed on the larvae. Rodents often eat the pupae in the soil. These agents are usually not adequate in urban settings.
Method 2: Mechanical Control, Egg Removal – If the needles containing overwintered eggs can be found before they hatch, they can be pulled off the plants and destroyed. Do not simply through on the ground since the eggs can still hatch.
Method 3: Mechanical Control – Colonies of larvae can be easily removed by clipping off the infested branch. Place these branches in a plastic bag and destroy. Colonies can also be knocked off by sharply striking the infested branch. Crush the larvae or knock into a pail of soapy water. If few colonies are present, they can be controlled using these methods but general spraying better controls large infestations.
Method 4: Biorational Insecticide Sprays – Several horticultural oils (often called “summer” or “verdant” oils) and insecticidal soaps are labeled for control of sawflies on ornamentals. These usually work well when the sawfly larvae are small and thorough coverage of the colony can be achieved.
Method 5: Spot Sprays of Insecticides – Many aerosol or hose end sprayable insecticides are available for spraying of colonies. This is usually adequate for most home landscapes. Nurserymen and Christmas tree growers often carry a small hand pump sprayer with an insecticide mixed for spot treating colonies. See Bulletin 504 for a listing of currently registered insecticides.
Method 6: General Insecticide Spraying This sawfly rarely infests large acreages unless controls have not been used for several seasons. General sprays may be warranted if more than 25% of the trees are infested. See Bulletin 504 for a list of currently registered insecticides. –By TreeHelp.com