A huge moth with a 4” wing span lands on a twig a few feet in front of you. This Great Ash Sphinx moth takes wing and flutters ahead to go lay its eggs in the leaves of a nearby ash tree. As the caterpillars develop, many will be eaten by birds, a sacrifice to ecosystem health. Those that survive will gorge themselves on ash leaves to give them strength for the amazing transformation they are about to experience. Squirming down underground after taking their fill of foliage, the caterpillars stay dormant all winter, pupating until the following spring, when they will emerge in June. Once they are able to fly, the next generation of this hardy native insect will spend their short but poignant life hopping from flower to flower, spreading pollen and helping ensure the survival of several other species of plants and insects.
If the ash tree isn’t there when this mature moth goes to lay its eggs, it will find another one of its favorite trees such as aspen, birch, dogwood or lilac to act as host for its brood of hungry little caterpillars. If, however, someone has used an insecticide on the tree to kill Emerald Ash Borer, our sweet, strong caterpillars unfortunately don’t stand a chance.
Emerald Ash Borer (EAB) is a fast-moving species of non-native beetle that is decimating ash tree populations. People are naturally alarmed, and pesticide companies have been eager to take advantage of the situation by stoking fear. Ash tree treatments are advertised on TV, billboards, the internet and local newspapers, often displaying menacing looking giant depictions of the Emerald Ash Borer.
What the companies providing the treatments don’t want to tell us is that the systemic insecticides they are injecting into ash trees could kill not just the EAB, but more than 280 native insect species that eat from ash trees. While many generalists like the sphinx moth can find other plants to eat from, every ash tree is a big buffet for beloved bugs including bees, moths and butterflies. The insecticides used to kill EAB are systemic, meaning they end up in every part of the tree: pollen, leaf, twig, bark, sap and root. Many of these pesticides are neonicotinoid based. Neonicotinoids are highly mobile in the environment.
Their mobility allows the pesticides to continue causing harm long after application. Neonics and other systemic insecticides are designed to kill insects who eat from any part of a treated plant. That means somewhere around 280 species of insects that are not the intended target of the insecticide could easily be harmed by these toxic treatments. Treating pollen providers like ash trees with pesticides places future generations of bees on a perilous path. Baby bees, or larvae, eat ash tree pollen gathered by adult bees. Adult bees eat ash pollen too, it is rich in protein. For a two-week period in the spring when they bloom, ash tree pollen is gathered by bees and delivered to larval chambers within the hive. Wild bees gather pollen from ash trees and other sources. Up to 25% of the pollen in larval chambers is from ash trees.
As a landscaper, I have begun to see the scope of the metropolitan pesticide problem. I consult at over 300 residential properties every year and there are ash trees being treated on better than a third of the landscapes I visit. Broadcast this treatment rate out over the entire state and it’s easy to see why we’re all noticing fewer and fewer insects every growing season. In addition, ash pollen is microscopic, it floats on the breeze and makes us sneeze. We all need to start asking ourselves if we feel comfortable inhaling systemic insecticides with each breath of spring air.
It has been estimated that fewer than 1 in 10,000 ash trees will survive EAB. With all this in mind, the longer we treat trees with insecticides, the more money we spend and the more insects we will poison only to delay the inevitable. The larger the trees become, the higher the cost for removal. Economically and ecologically, the simplest plan is to replace and remove. Replace first. Choose your favorite species of native or fruiting tree to start growing in the vicinity of your ash prior to removal. This will move the party so that native insects still have a place to live. Oak, quaking aspen, white pine, birch, hackberry, serviceberry, willow, and maple are all excellent options for supporting beneficial insects and local ecosystems. Consider planting in same species groupings so they can find each other underground to grow together. Include native understory woodland plants at their base to increase habitat potential and soil health. This will form a low-maintenance ground cover that can expand under the tree canopy over time. Sedges, ferns, columbine, woodland phlox, celandine poppy, Virginia blue bells, Jacob’s ladder, blood root, jack-in-the-pulpit, Solomon’s seal, Virginia waterleaf, lion’s foot and violets are a few fun options. Native plant nurseries will have many more. Watch your ash for signs of infestation including D-shaped holes in the bark, thinning and yellowing leaves and canopy and bark loss. Don’t wait till the infestation kills the tree because dying ash become brittle. When trees start to show signs of infestation, schedule a tree removal.
Trees become our friends over time. It is sad to see them go. Insects are our friends too. We have a choice to either imperil the well-being of hundreds of species of insects or we can learn to let go of one species of tree, and start planning today for a healthier future.
As the owner of Minnehaha Falls Landscaping, Russ Henry has guided and performed organic transition in hundreds of home landscapes and several schools, parks, condos and office landscapes. His practices are rooted in healthy soil, growing abundant and healthy landscapes without using any synthetic fertilizers, pesticides or herbicides.
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