Borers and Stressed Trees
Wood-boring insects are, in most cases, secondary pests — they attack trees that are already weakened. A healthy, vigorous tree has chemical and physical defenses that deter or kill boring insects attempting to enter. A stressed tree — from drought, root damage, disease, or declining vigor — loses these defenses and becomes vulnerable.
Understanding this is critical: finding borers in a tree is often a symptom of a deeper problem, not the primary problem itself. Treating borers without addressing the underlying stress is frequently futile.
Common Wood-Boring Insects in North Florida
Emerald Ash Borer (EAB)
Status: Not currently established in Leon County but spreading southward through Florida. Worth knowing.
Host: Ash trees (Fraxinus species). Kills ash trees regardless of tree health — it's one of the rare borers that attacks stressed and healthy trees alike.
Signs: D-shaped exit holes in the bark, S-shaped galleries under the bark, crown dieback starting at the top and working down.
Action: Ash trees in EAB's confirmed range should be treated preventively with systemic insecticide or removed if the tree isn't worth the ongoing treatment cost.
Ambrosia Beetles
These small beetles (genus Xylosandrus and others) bore into the sapwood of stressed trees to introduce fungi they farm for food. The fungi, not the beetles themselves, ultimately kill or damage the tree.
Signs: Toothpick-like "frass tubes" (wood dust pushed out in small cylinders) protruding from the bark. Can look like tiny pencils sticking out of the trunk. Multiple entry holes in the lower trunk.
Host: Virtually any hardwood or softwood species when stressed. Particularly prevalent on recently transplanted trees, drought-stressed trees, and trees in decline from root damage.
Action: Treat the stress condition. For high-value trees, preventive bark spray treatments reduce attack success. Once a tree is heavily infested, intervention may not save it.
Southern Pine Bark Beetles
Multiple species (Dendroctonus frontalis — southern pine beetle, Ips engravers, others) attack pines under stress.
Signs: Pitch tubes — small masses of resin and frass on the bark surface where the beetle entered. Sawdust-like frass at the base of the tree. Blue-gray discoloration of bark. Needles browning from the top down.
Host: Slash pine, longleaf pine, and other pines. Healthy pines "pitch out" beetles with resin; stressed pines can't keep up.
Action: Drought-stressed pines are particularly vulnerable. Healthy management practices (mulch, irrigation during drought) reduce vulnerability. Once a tree is significantly infested, removal is typically the outcome — there's no practical way to save a tree with a large-scale bark beetle infestation.
Flatheaded Borers (Metallic Wood-Boring Beetles)
The flatheaded appletree borer (Chrysobothris femorata) and related species attack stressed hardwoods, particularly under the bark on sun-exposed southwest-facing sides of the trunk.
Signs: Flat, S-shaped galleries under the bark, often on the sun-exposed side. Darkened or weeping areas of bark. Exit holes that are slightly oval in shape.
Host: Wide range of hardwoods. Common on recently planted trees whose bark is stressed by sun exposure and transplant stress combined.
Action: Trunk wraps on newly planted trees protect from sun scald and reduce borer vulnerability. Mulch and irrigation to reduce transplant stress. Remove and replace severely infested trees.
Laurel Wilt (Ambrosia Beetle Vector)
Worth specific mention: laurel wilt disease in the Tallahassee area has caused significant mortality in redbay, swampbay, and potentially sassafras. It's spread by ambrosia beetles carrying the Raffaelea lauricola fungus.
Signs: Rapid wilting and browning of leaves that remain on the branches (rather than falling), often occurring in mid-season. Distinctive blue-black streaking in the sapwood.
Host: All species in the laurel family in North Florida.
Action: No effective treatment — infested trees cannot be saved. Remove and chip promptly to reduce beetle and fungal spread to other trees. There is active research on resistant varieties and protective treatments, but nothing is currently commercially available.
When to Consult a Professional
Borer activity on a high-value tree warrants professional assessment. Accurate identification of the pest, assessment of the tree's overall health, and determination of whether preventive or remedial treatment is feasible all require hands-on evaluation.
We assess trees for pest activity as part of tree health evaluations. If you're seeing signs of borer damage on a significant tree, early professional assessment gives you the most options.
Questions about a tree showing signs of pest damage in Tallahassee? Call (850) 570-4074 or request an assessment online.