A purple ash borer trap hanging from a tree. Officials check traps for the presence of EAB.
With the identification of emerald ash borer (EAB) in a St. Paul neighborhood, and along the Wisconsin border near Houston county, so to come the advertisements from tree and landscape maintenance companies and retail products for treating and saving your ash trees. Hearing these radio spots and seeing insecticides for EAB on retail shelves would lead us to believe Minnesota is in a full blown infestation of EAB, and treatment is needed now.
The discovery of EAB is a revenue generating opportunity for companies. I recently received a flyer from a landscape maintenance service company with the headline of "SAVE YOUR ASH TREES'. Several items on this flyer concerned me after reading bulletins, alerts and fact sheets from various governmental agencies and university researchers about treatment options. So before we all get fired up and start dumping or spraying chemicals, let's understand the situation and the options.
Is treatment necessary?
The Minnesota Department of Agriculture is not recommending treatment outside a 15 mile radius of a confirmed infestation site. If your ash trees are more than 15 miles beyond this range, it is too early to begin insecticide treatments. Treatment programs that begin too early are a waste of money.
If your property is within a county that has been quarantined for EAB, your ash trees are probably at risk. Similarly, if your trees are outside a quarantined county but are still within 10-15 miles of a known EAB infestation, they may be at risk. Monitor where infestation sites are and watch ash trees closely for symptoms and signs of decline. If you notice a decline, contact an expert to determine the cause.
If your ash trees are at risk, and you choose to treat your ash trees, insecticide options are available. Research does show treatments can be effective, but it is worth noting that controlling insects that feed under the bark is difficult and that in university trials some treatments worked while others didn't. Put bluntly, there isn't one treatment that can guarantee 100% effectiveness.
Before You Treat a Tree
When you are making decisions about treatment and which tree company to hire answer these questions:
- Does your ash tree look unhealthy?
- Are you looking for a one-time treatment?
- Has the tree care company guaranteed treatment will save your tree?
If you said yes to any one of these questions, understand these points before you hire someone to treat the tree.
Studies show treatments work best when the tree is relatively healthy. A tree must be healthy enough to carry a systemic insecticide up the trunk and into the branches and canopy. When EAB larvae feed, the plant's circulatory system is damaged and water, nutrients, and the insecticide can't move through the tree. Ash trees having more than 50% dieback of its canopy are not good candidates for treatment.
Many of the treatments require annual treatments. One new product, emamectin benzoate, is effective for up to two years. It may take several years before the EAB population peaks and the threat is lower, but EAB populations may still be present. Scientists don't have enough experience to know how trees will react if they survive the initial wave of EAB.
As for company guarantees, no treatment has shown to be 100% effective. The flyer I saw gave the customer a 100% money-back guarantee of the treatment price for two years after application. My concern is it may take longer than two years for your tree to die from EAB. Another concern is if you were to treat now, EAB populations may peak two or three years from now, after the guaranteed period, and without repeat applications your tree is susceptible.
There are also recommended time periods to apply the insecticides. All insecticides, except cover sprays, are during mid to late spring, early May to mid-June, or mid-fall. The recommended time period is determined by the insecticide to be used. The companies that are advertising now, let's hope they are scheduling the treatments during the appropriate time frame.
Hiring an Arborist or Tree Company
Ask to see their certificate of insurance. The company should carry worker's compensation and personal and property insurance. If someone or something gets hurt or damaged on your property you could be held liable.
Ask if they are members of a professional organization or hire certified arborists. Membership to such organizations as National Arborists Association (NAA), the International Society of Arboriculture (ISA), or State Nursery Associations shows a commitment to continuing education and to the trade.
Ask how they will dispose of limbs and trunk. Infected ash products can not be removed from quarantined counties.
Clethera alnifolia, commonly known as summersweet clethra, has deliciously fragrant flower spikes that bloom during July and August, so plant it in a location where you can enjoy its sweet scent. Clethra's leaves are dark green and shiny and turn yellow in fall. Clethra prefers acid, moist, well-drained soils in full sun to shade. It will fail in a hot, dry location.
