Pesticides can be used for emerald ash borer treatment to save ash trees. Proactive management is necessary to combat the emerald ash borer to avoid infestation and death of healthy ash trees. EAB can be managed with a variety of strategies that prevent new infections and can actually save trees that are lightly infested.
Emerald Ash Borer is a non-native, wood-boring beetle that can attack all native ash tree species. This insect was first found in North America, in 2002, in southeastern Michigan and adjacent Ontario. It likely arrived in the early 1990s on solid-wood packing material from Asia. It has spread very quickly, largely due to human movement of firewood. To date, nineteen states and two Canadian provinces have confirmed EAB infestations, although there are still many uninfested ash trees, of all sizes in all affected states.
DISTRIBUTION OF EMERALD ASH BORER INFESTATION
2014 Distribution map of EAB Risk from the USDA:
HOW EAB KILLS TREES
EAB adults are 1/2-inch long and metallic green. They emerge through small D-shaped holes starting in late May and may be flying until early September. Moving ash wood products during this time of year presents the greatest risk for spreading the insect to previously uninfested trees and/or sites. The larvae may be found year round. They bore through tree bark, and feed in the cambium, creating long serpentine galleries which get wider as the insects grow. This feeding pattern interrupts the tree’s vascular system, eventually girdling and killing the tree. EAB can kill ash trees greater than 1 inch in diameter. In established infestation areas, most die within two to three years of becoming infested. Up to 1% of ash may survive on sites with heavy mortality. Some of these “lingering ash” show evidence of bark healing, suggesting possible host resistance.
Work is being done to identify and use native parasites and predators that have been found feeding on EAB, parasitoid wasps from Asia have been released in 12 of the 19 infested states as part of an operational biological control program. In study sites, parasitism has slowed the rate of EAB population growth.
To slow the spread of EAB there are state programs and a federal quarantine enforcement which restricts the movement of materials which might harbor the insect. It is difficult to control the spread of the insects that fly miles from tree to tree. But much of the spread of infestation has occurred because of human transport of infected wood which carries EAB to new areas, and this behavior can be managed. Also, if trees are showing signs of infestation on or near your property there are some things you can do to limit or slow the infestation, including removal of the host infested trees, and chemical treatment. The goal of EAB control is to reduce the expansion of the EAB population, to limit or slow the attack of healthy trees and spread to new geographical locations.
Remove Infected Trees
If you do not want to attempt chemical treatments (discussed below), then trees that are infected with or have died from EAB should be removed and properly handled to prevent continued propagation of the borers. These treatments include debarking, chipping, burning, burying or splitting, and drying the wood. Covering infested ash fire wood with plastic, burying the edges for 6 months, and then air drying for a similar time will kill the insects. Trees that die in summer should be removed and treated before the following spring which is when adult EAB emerge from the host tree as flying beetles.
Do Not Transport Infested Wood
Cutting up trees infected by EAB for lumber, firewood or tree trimming and transporting the infected wood to new areas will transport the EAB to infest and kill trees in these areas. Do not transport any wood or brush from EAB killed trees. Adult borers will still emerge in the spring and summer from ash fire wood which was cut the previous winter.
EAB is very aggressive, so few ash trees will survive an infestation. But there are things you can do to protect your trees. Chemical insecticide treatments can be conducted to protect and save valued trees. These applications include drenching the soil around the tree with insecticide, spraying the tree trunk, and trunk injection treatments. If done properly and at the optimum time of year, the insecticide will keep EAB away from healthy trees for a period of time. If a tree is lightly infested, the insecticide treatment kills or drives away the EAB and the tree can start to heal borer wounds and ultimately thrive again. Repeated treatments are needed every year or two to keep the EAB away from the tree.
This method involves mixing the appropriate concentration and volume of insecticide, commonly imidicloprid, diluted with water, and pouring onto soil or injecting into the soil around the base of the tree. The tree roots take up some of the insecticide as it moves downward through the soil, then the treatment is circulated throughout the tree, leaves to roots. Soil application of insecticides can take 6 to 8 weeks to reach the effective levels in the ash tree bark, so soil drenching with insecticide should be conducted in early to mid spring, or mid fall.
This method is relatively simple and easy to perform by landowners and the comparatively inexpensive insecticide imidicloprid is the weapon of choice. There are good instructions on the bottle labels for how to mix and apply as a soil drench around the trees.
There are environmental and and potential human health risks associated with soil drenching for EAB control. Dumping many gallons of insecticide on the ground year after year could cause slugs of insecticide to move past the tree roots downward through the soil, potentially causing groundwater contamination. And during frozen ground or flooding conditions, insecticide from these drenching areas could move overland to surface water bodies. Also the area around the tree will be a source of potential toxic exposure of pesticide to unintended receptors such as honey bees and other beneficial insects, and humans or animals that use the area.
With this method of EAB tree treatment, the lower portion of the ash tree trunk is sprayed with insecticide which penetrates through the bark and into the vascular system of a tree. The insecticide dinotefuran is used for this method, and is sold under the brands Safari 20 SG, Transtect and Zylam . Trunk spray treatments are done annually with dinotefuran.
Trunks spray is implemented by spraying all around the tree wetting the bark from the base up to about five feet high, taking care to avoid windy or rain conditions during application. The insecticide is quickly absorbed into the vascular system, and is circulated throughout the entire tree within two or three weeks. Trunk spray should be conducted during mid to late spring after trees have leafed out.
Using the pesticide trunk spray allows use of less insecticide than soil drenching, and limits ground discharge if conducted properly. But it does leave a potential insecticide exposure risk to any unintended receptors (humans, animals, birds, beneficial insects such as honey bees) which may come into contact with the treated bark.
Direct injection of pesticides through the bark and into the trunk of ash trees is an environmentally sound and economical way of treating EAB. With direct injection into the circulatory system of a tree, a much lower volume of chemical is needed because it all goes into the tree, leaving none on the ground or on the exterior tree bark for exposure to unintended receptors. Trunk injection is the most efficient and works the fastest of EAB control methods, with the pesticide circulation throughout the tree within a few days. Trunk microinjections should be conducted during mid to late spring after trees have leafed out and throughout the summer.
Healthy or lightly infested ash trees can be treated using an insecticide to prevent infestation by EAB. This can be easily conducted using Chemjet® Tree Injectors to inject pesticides such as injectable emamectin benzoate or injectable imidacloprid into small drilled holes at several locations around the circumference of the tree. The chemical is then carried throughout the tree, from up to the leaves down to all of the roots, effectively killing or driving away EAB currently in the tree, and preventing future infestation by visiting beetles.
A single injection treatment can protect ash trees for one or two years, depending on the type of insecticide used. Also, lightly infested trees showing initial EAB symptoms can be treated and recover.
Again, there are state and federal government pesticide rules which must be followed, so make sure the insecticide you want to use is allowed in your state and that you are following the directions on the label of the product. Also, certain insecticides may only be injected by tree professionals licensed for the product, such as some brands of emamectin benzoate. Other insecticides may be used by unlicensed but informed landowners, resort groundskeepers, and farmers, provided they are not listed on your state’s Restricted Use Pesticide list. If you are unsure of how to do this yourself then contact a tree care professional to help you save your trees.
With implementation of microinjection using the inexpensive Chemjet® Tree Injector, it is economical for protection of many more ash trees. This brings to reality an economical option of DIY tree injection for all of the healthy or lightly affected ash on your woodlot to save your trees and control continued expansion of the infestation.
Injection Procedure for Emerald Ash Borer
This example injection procedure for EAB is adapted from the Chemjet® manufacturer suggested procedure, and from the Ima-Jet tree injection insecticide label. Ima-Jet is 5.0% solution of imidacloprid, containing about 0.055 gram of imidacloprid per milliliter.
- Confirm with a tree expert that this procedure is appropriate for your tree. You may not have an EAB risk or there may be other circumstances that would cause this procedure to be inappropriate. Also there is always the risk that this procedure may harm your tree.
- Only inject ash trees during the seasonal time period necessary to be effective for treatment of EAB.
- Only inject trees after a good rain or after substantial watering. Do not inject trees during drought conditions.
- Plan for use of one Chemjet® Tree Injector every eight inches around the circumference of the ash tree.
- Put on rubber gloves and safety goggles for use during all mixing, injection and cleanup work.
- Disinfect Chemjet® injector and drill bit by washing and scrubbing in diluted bleach solution or Lysol disinfectant solution. Pull disinfectant solution through the nozzle filling the injector several times. Rinse with clean water.
- Prepare the imidacloprid injections per the labeled instructions. From the Ima-Jet label the maximum dose is 8 milliliters of Ima-Jet for every inch diameter of the tree. Calculations using this dose and typical tree diameters yield just under 8-inch spacing between injection points around the circumference of the tree using Chemjet Tree Injectors filled with 20 ml of Ima-Jet.
- Drill the first three holes at eight inch intervals around tree at 45 degree angle downward no more than 1.25 inch deep. Only use a 11/64 drill bit. Drilling more than three holes may heat up the bit and scorch the wood which will inhibit injection.
- Pull the chemical mix from step 7 into the injector until full at 20 ml and lock the handle back while twisting.
- Insert into recently drilled hole. Push into place and seal (don’t twist because the nozzle may break off).
- Using both hands, hold the Chemjet® in place and then twist and release the red plunger so that injection begins. If there is leakage push the nozzle in harder to seal. Repeat for remaining two holes.
- After all chemical is in tree, pull injector straight out of hole. If chemical starts oozing back out of open hole, replace Chemjet® and leave there for another half hour or use a plug.
- Repeat with three more holes, going around tree.
- If an injector is taking chemical slowly, leave it in place and move on. It could take up to 24 hours.
- IMPORTANT: Disinfect drill bit and all Chemjets (inside and out) before using on any other tree per step 6. Disinfect your hands and put on new rubber gloves to avoid potential for transferring diseases to next tree.
- Take Care of your Chemjet Tree Injectors after the work is done (or during long term work at least once per week) so they keep working smoothly by disassembling, washing all parts with hot soapy water, rinse and air dry, then lubricate the nozzle barrel and rubber plunger washer with silicone lube or vegetable oil before reassembly.
Some great resource links:
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