My tree company is recommending an extra emerald ash borer treatment, an extra treatment this year then returning to once every 2 years. I have 2 mature ash trees in my yard. Do you think treating 2 years in a row is necessary? Here is the company's email to me, I've redacted names. We at [Company name] hope you and yours are well, and that your trees are flourishing. Boulder County is a tough place to be a tree, and, with a changing climate, times are getting even harder. Tree irrigation is very important (call for more info on that). I am happy to report that the Neem-seed-based botanical insecticide we use, Lalguard Aza, (previously sold in a different formulation as “TreeAzin”) still has a near-perfect record in keeping our customers’ Ash trees from succumbing to Emerald Ash Borers (EABs). A few that began treatment very late did die. AZA has also been extremely successful in controlling numerous other insects that cause actual harm to trees in the Boulder area (for more on other insects we treat, scroll down three paragraphs). Why insert the word, “actual” into the above sentence? We at [Company Name]. are operating in an industry that, to achieve ever higher sales, has for decades used scare tactics about non-threatening, and even non-present insects and pathogens. We will not do that. Many chemical-pushing tree companies have also responded to the competitive environment by being less than candid about the products they apply to trees in customers’ yards. As a tree owner, you should not ever hesitate to ask hard questions about the nature and importance of any treatment that a tree company proposes. At the very least, you should insist on knowing the name of the product, so that you may independently investigate its efficacy, and perhaps also the impact it could have on non-target organisms. In this regard, pollinators are of particular concern, because they are very vulnerable to many systemic treatments commonly sold to homeowners. Insects gather pollen from plants regardless of whether they (or the wind) are the pollinators for a given species. In fact, peer-reviewed research shows that bees gather pollen from wind-pollinated trees almost exclusively early in spring. Pollen that could contain a lethal pesticide gets taken back to the hive and fed to the brood (See Severson and Parry, 1981). Aza is a safe and effective alternative. At [Company Name] we don’t address the full spectrum of insect pests that threaten Front Range trees, but here’s a list of some of the ones besides EABs that Aza is extremely effective at controlling: Flathead Borers (which are severely infesting English Oaks and Honeylocusts), Aphids, Elm Leaf Miners and Beetles, Oak Kermes Scale (kills the tips of Red and Pin Oak branches) and European Elm Scale (turns the bark on American Elms black). We don’t spray, we inject Aza into trees, usually every other year. It works on the larval stages of insects and has relatively short residual efficacy compared to most of the commonly used systemics. This means we must work hard to time treatments accurately; It also means the active ingredient is not available to non-target organisms, unless they’re present as larvae in the phloem near the time of injection. Because of its relatively short residual, Aza is virtually absent from leaves in fall. Due to overuse of very toxic systemic pesticides in Boulder County, it is a foregone conclusion that many of our fallen Autumn leaves have harmful residues in them. (See Kreutzweiser et al, 2009.) Of course, among the most harmful insects, Emerald Ash Borers pose the greatest threat to local trees. We will again be advocating “aggressive treatment” of Ash trees at peak infestation this year. This entails treatment in two consecutive years, one time (we are discontinuing fifth year back-to-back treatments, which has proven to be unnecessary) in those parts of the County under the worst pressure from the infestation. Specifically, we will be advocating that residents of Lafayette, Erie and Broomfield, and county areas between them, treat for two consecutive years. We will also apply this schedule in the first two years, to trees that started treatment late. Most other trees on our list are now on an every-other-year schedule. As in other years, we have regenerated jobs manually, tree by tree. That takes time, so again, Thanks, and have a great growing season!