Tree Borer Management: Signs Of Tree Borer Insects
By: Kristi Waterworth
Landscape trees burst to life in the spring, sprouting flowers in almost every color and young, tender leaves that soon expand to create puddles of shade on the lawn. But would you know how to identify tree borers if your trees didn’t behave predictably one spring? Keep reading to learn more about how to identify tree borers and treatment for tree borers once this becomes an issue.
What are Tree Borers?
Tree borers are a group of insects that lay their eggs on or inside of trees, where the young larvae eat their way through living tissues. These miscreants can be either beetles or clearwing moths, but the end result is the same. Tree borer insects cause affected parts of trees to slowly weaken as their chewing severs vital transport tissues. Over time, they may girdle trees or weaken branches to the point that they break under pressure.
The most obvious signs of tree borer insects are the tiny holes they cut into trunks, branches and stems. These holes may be perfectly round or slightly oblong, sometimes a sawdust-like material, called frass, falls on branches below these holes or forms a long cylinder as tree borer insects excavate tunnels.
Tree Borer Management
Treatment for tree borers can be difficult if adults are already present and laying eggs throughout the tree. Trees with many holes bored through the trunk are often easier to replace than to successfully treat, since the internal damage can be extensive after just a few seasons. Prevention is key if your trees are unaffected, but tree borer insects are active nearby.
Trees that are not infested, or have only a few noticeable holes, may be protected from borers by improving care. It may seem too easy, but borers are attracted to trees that are stressed and injured; pruning wounds are a common entry point for the first generation of invading borers.
Adding mulch around your tree and providing it with supplemental water and fertilizer will help it fight off borers and heal from previous damage.
Chemical Control of Borers
Trees that are riddled with borer holes are past the point of saving. These trees must be removed for safety’s sake; galleries can extend several inches past the penetration point, weakening limbs and branches that may snap with the first strong gust of wind. You must burn or otherwise destroy the infected tree’s tissues as soon as possible to prevent any borers that remain from escaping to nearby trees.
Chemical treatments are available for trees with minor infestations, though they generally are aimed at preventing re-infestation. Residual insecticides like carbaryl, chlorpyrifos, lindane and permethrin are designed to remain on tissues for many weeks, so that any insect that comes in contact with them will die immediately. All woody surfaces must be covered for these materials to work.
Imidacloprid and dinotefuran, systemic insecticides, can control borers that remain close to the bark layer of the tree, but should not be applied without identifying the pest inside your tree first. Sticky traps or pheromone-baited traps can be helpful in this department, but don’t rely on these traps to provide control for your borer problem.
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TREE ROOT BORER BEETLE CONTROL
Tree borer beetles include a wide range of insects which feed on trees. Some target specific trees but here in the United States, we have hundreds of species and many can thrive on a range of tree species. So if you discover a tree with some kind of boring pest, it could very well have different insects active.
In general, all tree boring pests are members of the beetle family though their shape, size and color can vary. Some are quite small, like the turpentine beetle and others can be several inches long like the hissing borer. Root borers can be massive reaching lengths of 3 inches or more!
Boring beetles will fall into three types: those which thrive just under the bark, those which bore through the trunk and those which live in the root system of the tree. And though some species can infest a tree without being noticed, others will produce piles of sawdust as they chew.
The bottom line is that once a tree gets a beetle problem, it will likely get worse and spread to other trees in the yard.
How to Treat Fruit Tree Borers
Stressed trees are the ones peachtree borers attack. The damage shows up around the bottom of the trunk in fall, but the stress began long before. Whether your fruit tree suffered from inappropriate watering, drainage, feeding or pruning, its basic care must be improved to help it resist these pests. Borers are young moths that hatch out as larvae on the base or canopy of a stressed fruit tree trunk. They bore their way inside the wood and live there, eating the inner wood, until the following spring. Peachtree borers attack stone fruit trees, leaving holes in the trunk that ooze a jellylike sap substance.
Prune off dead and infected branches from your fruit tree. Remove crossing branches and damaged branches, making the cut at a lateral branch at least 6 inches into healthy wood. Disinfect your clippers between cuts by rubbing with a clean cloth dipped in denatured alcohol.
Look for holes on the tree and dig the soil from around the bottom of the trunk to look there too, a likely spot for peachtree borers to enter the tree. Stick a sharp, narrow pocket knife or stiff wire into each hole and manually remove the larva. Take care not to wound the tree further.
Paint the trunk and lower branches of your tree with either carbaryl or endosulfan early in May. Repeat three months later.
Water your tree regularly and clean up debris and around the tree to help restore its vigor. Learn how to prune your fruit trees and apply the techniques regularly at the appropriate time. Fertilize with organic compost and composted manure rather than high-nitrogen fertilizers. Nitrogen-rich fertilizers encourage fruit tree borer attacks.
How to Prevent, Identify & Treat Borers
Here at our 60 acre family farm we take great pride in offering the healthiest and highest quality of trees found in the Metroplex. With that highly regarded reputation comes constant inspections for various pests and issues. To ensure that you keep your trees in the same high quality health as when planted, we are going to share more educational blogs this year to help everyone learn about what pests and issues to look for. Today we are going to be talking all about borers so you can all learn how to prevent, identify, and treat if needed.
In this blog we will specifically be discussing the following important topics:
- What are borers?
- Stages of a borer.
- Learn about the different types of borers.
- How to monitor and inspect your trees for borers.
- How to prevent borers from attacking your trees.
- How to treat your tree if it gets borers.
What are Borers?
Borer beetles are part of the Anobiidae (order Coleoptera) family. These adult pests are known for burrowing into trees and laying eggs inside the trees. These adult borers find sites for laying eggs by responding to chemicals and signals from stressed trees. Once the larva hatches then they feed on the inside of the tree and create tunnels. This causes additional stress to an already declining tree and can lead to a quicker death if not treated quickly. The tunnel can cut off portions of the vascular system of the tree and deprive it from sending nutrients up the tree.
Life Cycle of a Borer
Timing of life stages throughout the year will differ depending on the species of borer, your location and environmental conditions, but all borers go through complete metamorphosis with four life stages: egg, larva, pupa and adult.
- Eggs – Laid when adults are mating on or near the host plant. Common egg-laying sites are on or under bark, in leaf litter/detritus on the ground, and in cracks of tree trunks or branches.
- Larvae – Once hatched they bore into the host plant using digestive enzymes and begin feeding. Feeding will increase progressively as they grow.
- Pupae – Some borers pupate in or on the host plant others drop to the soil and pupate there. No damage is done during this stage.
- Adults – Emerging from the pupae, adults mate and seek out optimal sites for eggs to be laid.
Learn About the some Common Types of Borers in North Texas
Clearwing and flatheaded borers are the main types that attack woody ornamentals. The groups differ somewhat in their habits and host preferences, which can affect the approach for controlling them with insecticides. The key to controlling these pests are to keep plants healthy and, if necessary, to treat during the Spring and Summer when borers are vulnerable to insecticides.
Iberia haldemoni, a longhorned borer beetle. Photographed by Lauren Miller. parelaphidion aspersum, a longhorned borer beetle. Photographed by Lauren Miller.
How to Monitor and Inspect Your Trees for Borers
Borer beetles are most easily identified by the round, oval or D shaped holes that they burrow in the tree trunks. Also keep an eye out for large holes that are leaking sap like the below pictures. You might also see sawdust like material on the ground or in the cracks of the bark.
Some people do misidentify borer holes for woodpecker holes. Just know that woodpeckers also carve a series of holes together, while the borers burrow just one hole in an area. If you have several borer beetles then you could see several holes randomly placed around your tree trunk, but never in a row like the woodpeckers holes.
Borer beetles attacking a sick tree. Borer beetles attacking a sick tree.
How to Prevent Borers From Attacking Your Trees
Borers prefer trees in stress or decline, and truly the best way to control these pests is by keeping your trees and shrubs healthy. Planting trees properly and not wounding the trees while planting or mowing around them is also important. But should your tree get borers, then not all is lost and you can try treating it.
How to Treat Your Tree if it Gets Borers
If the borer beetles have already burrowed inside the tree then insecticide sprays will not be effective. Products must be applied during the Spring or Summer while the larvae or eating on the tree so the chemicals are actually ingested. Systemic insecticides (azadirachtin, emamectinbenzoate, imidaclprid) applied with a trunk injection works well along with bark sprays and soil drenches (dinetofuran and imidacloprid). Our favorite product to recommend for flatheaded borers is Bayer Advanced 12 Month Tree & Shrub Protect & Feed. It is a soil drench and the active ingredient is imidacloprid. You will need to treat your trees a couple times, and please make sure to always read and follow label directions for safe use of any pesticides. If you feel overwhelmed with applying these treatments yourself then you can always hire a local arborist to help you.
I really hope that you have found this blog helpful. We will continue sharing about some of the pests in North Texas so all of our customers and followers can feel more prepared and informed for any pest that comes their way.
Pests in Gardens and Landscapes: Quick Tips
Bark beetles make tiny holes in tree trunks and branches.
Flatheaded borers produce large exit holes in trunks.
Clearwing moth larvae bore large holes and leave sawdust-like frass.
A number of different types of insects can bore into tree trunks and branches as adults or larvae, producing sawdust or sap-filled holes and weakening trees. Most borers can successfully attack only trees that have been stressed by improper irrigation or care, disease, or mechanical injury. However, some invasive insect borers attack healthy trees. Usually by the time a tree is infested with borers, there is little you can do to manage them other than to improve tree vigor, prune out infested branches, or remove the tree. Insecticides can be used to prevent infestations of borers on high-value trees.
To avoid a borer attack, keep trees healthy:
- Plant tree species adapted to your area.
- Irrigate trees properly and separately from regular lawn watering.
- Avoid mechanical injuries to trunks and roots.
- Protect tree trunks and branches from sunburn.
- Avoid pruning trees when borer adults are flying, usually late winter through late summer.
- Replace old declining trees.
- Monitor tree trunks and branches regularly to detect infestations before they become serious.
Correct borer identification is essential.
- Effective management practices vary by insect species.
- Confirmation of species requires finding the insect, although knowing symptoms and host plant species can help narrow down the possibilities.
- Many tiny holes in tree trunks and branches may indicate bark beetles larger open tunnels filled with sawdust-like boring dust (frass) indicate clearwing moths flatheaded or roundheaded borers leave wet spots and dark stains and D-or 0-shaped emergence holes.
Nonchemical ways to manage tree borers:
- Follow guidelines for keeping trees healthy.
- Prune out infestations of bark beetles and other boring beetles on branches.
- If the main trunk is extensively bored, remove the tree and focus on protecting neighboring trees of the same species.
- Clearwing moth larvae can be killed by probing tunnels with a stiff wire.
- Apply beneficial Steinernema nematodes to kill clearwing moth larvae.
What about pesticides?
- Limit pesticide (insecticide) use (sprayed or systemic) to protecting healthy trees and combine with other nonchemical methods to improve tree defense.
- Insecticides are most effective when applied before adults land on the tree to lay eggs on trunks or branches or bore in. Careful timing is essential for success.
- Insecticides won’t save heavily infested trees because they have limited impact on borers already inside the tree.
- If treatment is warranted, use persistent insecticides labeled for bark treatment such as carbaryl or certain pyrethroids. Effective insecticides for wood borers are available only to licensed applicators.
Minimize the use of pesticides that pollute our waterways. Use nonchemical alternatives or less toxic pesticide products whenever possible. Read product labels carefully and follow instructions on proper use, storage, and disposal.
Statewide IPM Program, Agriculture and Natural Resources, University of California
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