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PLANT HEALTH CAREANT HEAL By Br andon Gallagher Watson Tree health practitioners are frequently asked to assess and diag- nose tree problems.On most days this is not too hard. In any given area, most trees have three to five common issues and this makes the diagnostician’s job fairly easy. Properly identify the tree, run through your list of common ailments for that species,and then use your judgment and experience to key in on the right one. Now that you have your culprit, you can open up your tree health protocol playbook, and choose your management strategy from the known, predictable solutions.This method works great when the pest has readily available manage- ment protocol and you can properly set the client’s expectations.There are, however, many times where the management is not so straight- forward and the job becomes more difficult. The client, however, is still looking to you to solve their problem, so what do you do for management of difficult-to-control pests? Where do we start? First, we need to understand what makes a pest difficult to manage.There are several rea- sons why we might call a pest “difficult.” One problem may be that we do not yet have a well- developed management protocol. This is often the case with newly introduced pests, but many times we at least know where to start.A newly introduced exotic pest can wreak havoc on native trees that have no natural defense; however, if we have experience with a similar or related species we can use that as a starting point. For example, if a new leaf-feeding beetle pops up on the East Coast,we have proven management tools of other leaf-feeding beetles, such as Japanese beetles,so we could try a similar management approach to develop an effective protocol. If it proves successful,we now have a plan in place. When emerald ash borer (EAB) was first discovered in the United States arborists and researchers were able to implement treatment plans that been used for many years to manage bronze birch borer (BBB) as these two insects are closely related. Just because it worked before… The case of EAB actually brings up another factor that makes a pest difficult to manage; and that is a poor response to current 22 Arbor Age / March 2011 management tools.Although we had a starting point for EAB by using a protocol similar to BBB, it quickly became apparent that EAB was going to be a different challenge that would require a different management strategy. Although BBB was effectively controlled using soil-applied imidacloprid, EAB treatments seemed to have mixed results, especially on larger trees. Apple scab can be considered operationally difficult as it always requires spraying. Questions were asked regarding why EAB was responding dif- ferently.Was there something about the uptake in ash versus birch trees? Were the EAB larvae more resistant to the product? Was it application timing? Was it that the current label rates were insufficient? Researchers looked at all of these questions and dis- covered that by applying imidacloprid at higher rates on larger trees they were able to get the same effective control of EAB that were seen on smaller trees. Now, by using an imidacloprid product labeled to protect larger trees, arborists have a soil- applied management strategy that can provide predictable results. Do we have the right tools in the toolbox? Sometimes the management challenge is a lack of available management tools altogether. Not every ash tree can or should www.arborage.com