How to protect your trees from borers and other silent killers

How to Protect Your Trees from Borers and Other Silent Killers

1. Why your trees might be under siege (and you don’t even know it)

When I was out in the field, one of the things that surprised many homeowners and property-folk was how quiet the killers could be. It isn’t always the obvious insect chewing on leaves, or a huge fungus you can see from the street. Some of the worst damage is done inside the tree or beneath the bark — and by the time you realise, the tree is already in serious trouble.

One of the usual suspects: borers. In Australia, the group known as longicorn borers (also called longhorn beetles) target a range of trees. They spend their larval lives tunnelling through the cambium and heartwood, sometimes for years, weakening the tree slowly.

Here are a few key facts every gardener/handyman/landscaper should know:

Borers often go after stressed trees - those suffering drought, root damage, compacted soil, heavy pruning or other stressors.

You may see small holes in the trunk or limbs, fine frass (sawdust-like debris), or sap/“kino” bleeding from the tree’s bark. These are early warning signs.

• Some of these pests bring in secondary issues - fungi, rot, structural weakness - making the tree unsafe or dead. For example, with certain exotic borers/associated nematodes the damage can be rapid.
• Because the damage often happens beneath bark or inside the trunk, visible foliage may look okay until later stages - meaning big risk for “silent” kills.

So yes, your trees might be under threat even if they look pretty good at the moment.

2. What you need to look out for (inspection checklist)

Here’s a field-friendly checklist I used when inspecting trees for clients. Whether you’re a homeowner, gardener or landscaper, you can walk around your site and check for these.

Inspection points:

• Check the base of trunks and major limbs for tiny holes (often oval or round) where adult beetles have emerged. Fine frass under or near these holes is a tip.
• Look for bark that is loose or flaking, bark that has detached from wood underneath, areas of sap bleeding or “kino” (reddish resin). These can all indicate the tree is trying to defend itself from larval tunnelling.
• Review the overall health of the tree: is growth stunted? Is foliage thinner than usual? Are there more dead limbs than expected? Stress makes a tree more vulnerable.
• Inspect soil, roots and environment: compaction, low water, damage from lawn equipment, pruning wounds, or root disturbance all increase risk.
• If you suspect something exotic (especially in coastal or urban fringe areas), check with your local biosecurity authority - some pests are regulated.

3. Prevention is better than cure

Before investing large sums in treatments, I always emphasise: make the tree strong. A healthy tree is far more resilient. Here are maintenance tips I used routinely:

• Ensure adequate watering during dry spells, especially for young trees or those in compacted or poor soil.
• Mulch around trees (but not piled up against the trunk) to maintain moisture, moderate soil temperature and avoid root stress.
• Avoid unnecessary wounding of trunk/roots: keep lawn mowers and string trimmers away from trunks, protect bark from mechanical damage.
• Prune correctly (when needed), remove dead or dying limbs safely. Make clean cuts and avoid leaving large stubs.
• Improve soil aeration if compaction is an issue. Good root health equals good tree health.
• Avoid over-fertilising short term, which can cause flush soft growth — this is more attractive to pests.

When you’ve done the above, you’re ready to add targeted treatments for borers and other internal threats.

4. Treatment options: what works and what to look for

From my days in commercial pest control, treating trees for internal pests like borers requires a combination of surface applications and sometimes systemic uptake (depending on the pest & tree species). Note: always follow label directions, local regulations and ensure correct protective equipment.

Here are three product recommendations from our range at Pest Wholesale that are well-suited for tree protection — keeping in mind you must check suitability for tree species, pest species, and local regulations.

Product Picks

• CroPro Zeus Termiticide and Insecticide: A broad spectrum insecticide treatment with bifenthrin, suitable for subterranean pests but also many wood boring and insect pests. Ideal for treating around base of tree, root zone and as barrier protection.
• Surefire Fortune Ultra Termiticide and Insecticide: A professional-grade product with excellent residual and penetration characteristics. Good for serious infestations or where you suspect tree internals are compromised.
• CroPro Buzzard Insecticide: A more general insecticide (for smaller scale applications) that can be used recently to treat tree trunks/branches for early signs of borer activity (when applied per label).

Treatment Approach

1. Identify the pest - If you’ve seen entry holes/tracks, you may already have infestation. Choose a product geared for that level of assault.
2. Apply to trunk and root zone - Surface treatments around base and lower trunk can kill adult beetles emerging from the tree and reduce larval entry.
3. Consider systemic/root uptake options - For deep bore infestations, the product must enter the tree’s vascular system; some product labels will specify tree injection or soil drench near roots (check suitability!).
4. Follow up and monitor - Application alone is rarely enough. You must monitor over time (6 months, 12 months) for new holes, fresh frass, bark damage, leaf decline.
5. Record & repeat - Keep notes on date, product used, tree species, observed damage. If you’re doing multiple trees, you’ll see what works for your site.

5. What to do when you catch it late

When the infestation is advanced, sometimes the best option is removal. If a tree is structurally compromised or has large internal tunnelling, it poses a safety hazard (falling limbs or collapse).

In such cases:

• Consult an arborist to assess structural integrity.
• If retaining the tree, look at combining treatment with structural support (cabling, bracing) and removal of dead limbs.
• Monitor neighbouring trees too — some pests spread or shift hosts.
• Dispose of removed material properly to avoid spreading pests (e.g., don’t just chip and leave infested wood onsite).

6. Final thoughts

Putting it all together: keeping trees safe from “silent killers” like borers means being proactive. Don’t wait until the foliage is dying or big limbs are falling. Walk your yard or site regularly, check trunks, bark, base of trees, soil conditions, and treat early.

With a few good maintenance practices + targeted treatments like the ones listed above from Pest Wholesale, you’re putting yourself in a strong position to keep your trees healthy for years to come.

If you’d like help choosing the right product for your tree species (some species are more susceptible than others) or for specific borer or pest species, I’m happy to dig deeper and pull up labels or case-studies for you.

Stay vigilant — your trees deserve it.