Sustainable Southern Gables on Guard Against Invaders

One of the nice things about living in Southern Gables is the rich array of activities and experiences available right here in the neighborhood. The “Sustainable Southern Gables” organization, for example, offers free classes, excursions, and workshops on a regular basis with the aim of helping us to be better stewards of the environment. Last Saturday, SSG hosted a free class on protecting our beautiful ash trees from an invasive pest, the Emerald Ash Borer (EAB). The City of Lakewood Forester, Luke Killoran, conducted the class on the campus of Green Gables Elementary School. Luke is a resident of Southern Gables and so he has a personal interest in our tree cover as well as a professional hand in protecting it. The Green Gables School campus was a particularly appropriate venue because of the number of ash trees there. Providing cool shade and beauty, they frame our little school with a welcoming and attractive environment. 

We have read a lot about the EAB in recent years as it has gotten closer to Lakewood, but this hands-on class brought the message home to the participants. The message is this: the trees are not doomed. Early identification of an infestation is key, and now is the time of year to check for infestation and begin treatment. Luke showed the points of identification of an ash tree, including the compound leaf with leaf stems joined straight across from each other, and the diamond-shaped ridge patterns on the bark of mature trees.

As of this writing, the EAB has not appeared in Lakewood, but the City Forestry Department is continually monitoring for it. Proactive treatment is underway for ash trees on public property, using appropriate insecticides. The EAB is susceptible to a number of insecticides, and treatment is by direct injection into the tree or soil drenching. Some insecticides must be applied by licensed applicators, and some can be used by homeowners.

In our spring 2022 newsletter, Ken Fischer told us that symptoms include branch dieback near the top, D-shaped exit holes 1/8-inch wide, serpentine tunnels under the bark and new sprouts on the trunk and branches. Proactively checking your ash trees for evidence of infestation can give you a head start on preventing further damage.

The Lakewood Forestry Department has information online about the EAB among other Invasive Insects, and we published the following article last year for background and cautionary information. 

By Marcel Guajardo

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The Emerald Ash Borer, or EAB for short, is a tiny beetle about 0.3 inches long that originated from northeastern Asia. Known for its shiny, emerald color, it was first discovered in the United States in 2002 in Michigan. It likely was introduced from shipping materials and pallets from overseas. In its native habitat in Asia, the ash tree species have evolved to resist EAB, and predators include a species of parasite wasps that were only recently introduced as a biological trial in certain areas of the United States. Outside of its native habitat, it is highly destructive to ash trees throughout Europe and the United States. It has spread throughout the U.S. and has been found in every state east of Colorado. In Colorado, the Boulder area was the first “ground zero” for the EAB. The city of Boulder has spent a considerable effort to manage the spread of EAB, including measures such as removing ash trees, chemically treating healthy ash trees in public right of way, and educating the public.

Leaf cluster. Photo from Colorado State Forest Service.

First though, do you know if your or your neighbor’s tree is an ash? In the spring when leaves come out it’s easy to tell – the individual leaves are over with a pointed tip, and grow in groups with leaf pairs joining to a woody stem directly across from each other and a single one at the end. In winter or early spring it’s not as obvious but you can see the branches are all across from each other rather than staggered, and the bark of a mature ash will have diamond-shaped ridges.

Diamond pattern bark on mature ash tree. Photo from Colorado State Forest Service.

The beetle kills the ash trees by laying eggs into the crevices of the bark of the tree. Once the larvae hatch, they chew on the bark and the outer layers of the tree trunk, creating tunneling that prevents the tree from distributing water and nutrients properly, thus killing it gradually.  Once a tree is infested, it is only a matter of time until the tree dies, and this varies between 2 to 5 years. Once a neighborhood is infested, all ash trees are expected to die within 10 years unless mitigation is taken.

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Adult beetles prefer to lay eggs on stressed trees but don’t avoid healthy trees altogether. If you have an ash tree that you don’t regularly water, it will more than likely be susceptible to EAB infestation. While there are various Ash tree types, including green ash, black ash, white ash, and blue or sometimes known as purple ash, the green ash and black ash are the most susceptible to EAB. The blue or purple ash tends to exhibit the highest resistance to the EAB, likely due to a higher amount of a chemical called tannin which the EAB does not prefer. The EAB can survive in outdoor temperatures down to about -22F, so a significant, sustained cold snap is required to mitigate the population. There are a few actions you can take to protect and mitigate your ash tree. First of all, you want to regularly water and prune the ash tree to keep it healthy. The healthier the tree, the less likely that the EAB will be able to wreak havoc on it. However, it is expected that all ash trees will eventually become infected and die due to EAB, so you might be just buying time and making it less susceptible that your ash tree is one of the first to be infected. To give your ash tree the best chances of surviving EAB, you can have a certified arborist apply an insecticide. For our single, majestic green ash tree, we have a company called The Natural Way come every other summer and inject an insecticide into the trunk of the tree. We’ve been doing this for the last 4 years, and so far, there is no evidence of EAB in the tree. Doing this in perpetuity will prolong the life of the tree by avoiding EAB infestation. Another option is that you may elect to remove the ash tree, especially if it already shows signs of infestation or stress. The common sign of this is a tree whose canopy is dead, and new branches or “shooters” are growing at the bottom of the trunk.

Marcel Guajardo is originally from Houston but came to South Lakewood early enough to say he grew up here. He and his family are writers, artists, and musicians, and love the Southern Gables area for its arboreal beauty. Marcel has a green thumb and is a reliable authority on tree care.

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