Plant Health Care Line: 720-626-2411
2023 Letter to EAB Clients
This year will mark our 9th season of treating Ash trees for Emerald Ash Borer. Our pollinator (and human) safe product, Lalguard Aza, has been remarkably successful in treating EAB – we have still not lost one tree that has been treated on schedule. After nine years, enough time has passed that I think it might be useful to review the nature of these insect pests.
Emerald Ash Borers, which are a variety of flat-headed borer, have been in Boulder since at least 2010, but probably longer. Historically, these insects have proven more deadly to native North American Ash than any other insect attacking any other tree species on the continent. They likely arrived here in a load of firewood brought from the Upper Midwest and spread quickly to all parts of town. Adults over-winter in Ash trees, emerge in spring, feed on leaves (typically on the same tree they emerged from or one close by—they are “lazy flyers”), mate and lay eggs on the bark. The larvae hatch, typically, in early summer, eat their way into an Ash and begin to tunnel around in the outer vascular system. Their numbers increase year by year, and over time they disrupt enough vascular tissue that, absent intervention, they kill a tree in about 8 years.
It is quite difficult to detect the presence of EABs in a tree during the first few years. Subtle signs start to appear in about year 3; but by then the insects have gained a foothold. We heard experts from the Upper Midwest state, early on, that the geographical spread of an EAB infestation is almost always ahead of where the public thinks. Recent local observations confirm this – for example, the first trees identified with the borers in Louisville were already so badly infested that they had to be removed. For this reason, entomologists have consistently advised that people begin treating before the insects have been identified in their locality, and certainly before overt signs are detected in the tree(s) in question.
Most of Boulder County is now well beyond the early stages of EAB infestation: It has long since spread north, east and south; trees are now infested in many other parts of the Front Range. And although most untreated Ash in Boulder are dying or have died, there remain a few (afforded a “halo of immunity” in some small pockets around town where enough neighbors have treated consistently), that are still treatable. If you are counting on such outlier trees continuing to live, do not: There is no evidence in the US of any Green or White (including Autumn Purple) Ash having genetic resistance to EAB. Though the numbers of EABs in some parts of Boulder are undoubtedly lower than they once were, many of the remaining insects are starting to thrive in previously treated, but lapsed, trees, or in small previously overlooked trees. We can help you get started or get back on schedule – give us a call – we will assess which trees are treatable and quote a price.
For several years now, we’ve been advising an “aggressive schedule” for treating Ash at the peak of infestation. (As a reminder, this schedule involves treating in back-to-back years at least once, and possibly twice, depending on a variety of factors). Because of the favorable (wet) weather conditions this past year, the declining population of insects in some parts of the County, and the effectiveness of AZA, in keeping EAB’s at bay, we are not pushing a second back-to-back year this coming season. This means that if we treated your trees back-to-back (years one and two), then skipped a year, then treated in the fourth year, you can probably skip year five.
Ashley, as always, is tracking the history of each of your Ash trees. Her work number is: 720-626-2411, if you have questions or would like to order treatment.
Thanks for staying with and trusting us; after 35 years we are very grateful for your continued support and look forward to working with you for many more years. Our seven climbing Certified Arborists and additional two climbers continue to provide a range of other arborist services, including planting, pruning, technical removals, stump grinding and tree risk assessments. We also treat a range of other insect pests with AZA – it is extremely effective against Elm Leaf Beetles, Elm Leaf Miners and European Elm Scale, as well as Oak Kermes Scale and a range of flathead borers and aphids. Please let us know how we can help, and we’ll send out an Arborist.
Sincerely,
Fred Berkelhammer, President
What is the Emerald Ash Borer?
The Colorado Department of Agriculture reports:
Emerald Ash Borer (EAB) was found in Boulder, CO, in September 2013. As a non-native insect, EAB lacks predators to keep it in check. … [It] is responsible for the death of millions of ash trees …
The City of Boulder reports:
EAB is a federally quarantined, invasive tree pest … [Since its discovery in Michigan in 2002], the small green metallic colored pest, originally from Asia, has spread … to 21 states, unfortunately now including Colorado.
How to recognize it
EAB is very difficult to detect in the early stages of attack; sometimes visual signs do not appear to the untrained eye for 3 or 4 years after the first borers arrive. Later, the signs, as shown in the images to the right, include:
- The metallic-green adult beetle is tiny and bores out of the tree via tiny D-shaped holes. (right)
- Years after the initial invasion, trees show loss of foliage at the crown with new growth at the base. (top right)
- The larvae live under the bark, burrowing serpentine galleries into the sapwood which disrupt the flow of water and nutrients. (bottom right) Eventually, the bark may crack.
What should you do about it?
Ash trees may be removed or treated. When treated, there are four basic control options:
- Soil applications of systemic insecticides.
- Spraying non-invasive systemic chemicals onto the trunk.
- Spraying persistent contact insecticides onto the bark of the entire tree.
- Injections of systemic insecticides into the lower trunk which then move systemically up the tree. These include AZA®, the preference of Berkelhammer Tree Experts.
AZA®, a formulation of Neem Tree seed extract, or Azadirachtin, is injected into Ash trunks in late Spring through mid-Summer. Unlike the other treatments, this product is completely bee-safe and, unlike some of the alternatives, it breaks down before the leaves fall in Autumn.
View this explanatory video about AZA® from Oakville, Ontario.
