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Keeping Your Pines Healthy:
Defeating Destructive Borers

In the world of trees, especially cone-bearing ones like pines, dealing with borers can be a real challenge. These tiny insects can wreak havoc on stressed trees, and sometimes, even healthy ones. This article is your guide to understanding and managing these sneaky borers to keep your pine trees thriving.

The Impact of Extreme Weather

In July 2023, our region faced record-breaking heat and erratic rainfall, leaving our landscape trees in a vulnerable state. Cone-bearing evergreens, like white pines, are particularly sensitive to drought and flooding. These environmental stressors weaken the trees’ natural defenses against borers. To make matters worse, borers have an uncanny ability to sniff out stressed trees. Recovering from a drought can take years for a tree, which is why it’s important to keep an eye on them for any early signs of trouble.

Early Detection is Key

Taking action early can prevent infested trees from becoming breeding grounds for borers, which could ultimately harm your entire tree population. If a tree is more than halfway dead or if most of its needles have turned yellow, it’s usually beyond saving. In late fall or winter, these trees should be removed to eliminate reproducing borers from your landscape before they can harm healthy trees. For an extra layer of protection, you can apply insecticides directly to the trunk to kill boring insects. Healthy trees near infested ones can benefit from soil-applied insecticides, like imidacloprid or dinotefuran, applied during the fall and early spring.

Meet the Borers

  • Zimmerman Pine Moth (ZPM): These moths commonly target pine trees in late July. They lay their eggs where tree branches meet the trunk and survive the winter in cracks. Come spring, when forsythia blooms, their larvae burrow into the trunk, causing damage. Insecticides are most effective against ZPM during these two critical times of the year. Note that soil-applied imidacloprid isn’t particularly effective against ZPM, and this borer poses a threat to spruces and most pines.
  • White Pine Weevils: These pests attack the central leader of pine trees, especially when forsythia blooms in early spring. Pruning infested shoots before adult weevils emerge can help, as can early spring application of long-lasting insecticides or soil applications of imidacloprid.
  • Bark Beetles: Several species of bark beetles go after pines in Indiana. They’re most active in April and May when they attack trees. After mating in the spring, they lay eggs beneath the bark. These eggs hatch and create distinctive patterns before becoming adults in mid-summer and again in September.
  • Pine Sawyer Beetles: By the time pine sawyer beetles target pine trees, they’ve often been attacked by bark beetles and may even have nematodes that cause pine wilt disease. In these cases, removing the tree is usually the best control option.


When it comes to pine trees, keeping them safe from borers is essential for their health and longevity. Acting early, understanding the types of borers, and using the right insecticides can help you win the battle against these sneaky invaders and ensure your pine trees stand tall and strong. So, by staying active and following these strategies, you can enjoy the beauty and benefits of your thriving pine trees for years to come.



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