Description and Biology
Southern pine sawyers, Monochamus titillator, are longhorned beetles that are common in North Carolina. These beetles are up to 1.5 inches long and are mottled and blend in with pine bark. The “horns” are actually antennae that often much longer that the rest of the insect. Southern pine sawyers are very sensitive to the health of pines. Very soon after a pine reaches the "point of no return" or is cut down, adult sawyers soon fly in to chew oval, conical holes in the bark in order to lay eggs underneath. Sawyer larvae hatch and bore in the sap wood for a while excavating shallow tunnels filled with wood fibers and frass. These roundheaded borers are legless and fairly slender. Older larvae then tunnel directly into the heart wood and before pupating close to the bark about a year later. The larvae are called roundheaded borers because their tunnels are round. They are called sawyers because as they feed, these grubs make a clicking or rasping noise that can be heard several feet away. In addition, “sawdust” accumulates around the base of infested pines. Adults molt from the pupae and emerge by chewing round holes in the bark. New adults feed on the bark of healthy pines before mating and laying eggs. In warm weather, sawyers develop from egg to adult in about two months. Development and adult activity is much slower in cold weather. This is a main reason pines are best cut in the winter for log homes. In warm weather southern pine sawyers soon infest newly cut logs and degrade the wood with their tunnels. Pinewood nematodes are carried by sawyers and perhaps other beetles. New sawyers feed on the bark of pine twigs and infest the new tree with nematodes from the tree the beetle emerged from. Because sawyers feed on the bark of healthy trees, it is possible for such trees to become infested with pinewood nematodes at that time.
Southern pine sawyer beetles are about 1.5 inches long.
Southern pine sawyer feeding damage.
Southern pine sawyers grubs are relatively slender.
Southern pine sawyer pupae are found under the bark.
"Sawdust" collects around the bases of sawyer-infested trees.
Host Plants
Pines are the principal host plants of southern pine sawyers. Trees in woodlots that are killed by bark beetles or other factors are invariably infested by sawyers. Dying or dead pines must be salvaged rapidly to avoid degradation by sawyers. Once inside the tree, sawyer larvae can survive milling and planing as long as the blades actually miss the insects. As the wood dries out, development slows and sometimes the adults do not emerge for several years (and then bore out through the sheet rock or through the flooring!).
Residential Recommendations
Because southern pine sawyers are active throughout the growing season, there is no practical way to control sawyers other than keeping trees in good health (avoiding soil compaction, irrigating in dry weather, proper fertilizers etc).
References
- Insects of Eastern forests. Drooz, A. T. editor. 1985. United States Department of Agriculture Forest Service misc. publication 1426.
- Not all Pine Beetles are the Notorious Southern Pine Beetles!! Reid, L. No Date.
- Pine Sawyer Beetles. Anonymous. No Date. Digital Diagnostics. Entomology & Plant Pathology, Oklahoma State University.
- Extension Plant Pathology Publications and Factsheets
- Horticultural Science Publications
- North Carolina Agricultural Chemicals Manual
For assistance with a specific problem, contact your local N.C. Cooperative Extension Center.
This Factsheet has not been peer reviewed.
Publication date: May 10, 2016
Revised: Oct. 14, 2019
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