As you walk through your neighborhood, you’ll likely admire the canopy of ash trees or their vibrant display in your autumn garden. Ash trees, frequently seen lining city streets and parks, provide not only shade and oxygen but also sustenance and habitat for wildlife. However, since the arrival of emerald ash borers (EAB) in 2002, these trees have been rapidly declining. Despite their striking appearance with slim, shiny shells, these invasive pests measure only ¼ to ½ inches long and can devastate even the hardiest ash trees.
Onions Australia had an exclusive conversation with Andrew Conboy, an ISA-certified arborist from Philadelphia, about recognizing EAB damage and addressing infestations. “The earliest signs of emerald ash borer (EAB) infection in an ash tree include crown dieback (a sudden increase in dead branches in the tree’s crown), heightened woodpecker activity (as they pursue EAB larvae), and epicormic sprouting (new shoots sprouting from the trunk, large branches, or the tree’s base),” Conboy explained. He noted that these pests leave holes throughout the trunk, marking where insects emerge from the tree.
“Discovering any of these D-shaped holes is a definitive indicator of EAB infestation,” he stated. “Typically, other ash pests are native and don’t cause significant dieback or a rapid deterioration in tree health. Observing these issues is also a good indicator.”
What to do if you notice signs of emerald ash borer infection
Upon identifying signs of an emerald ash borer infection, treatment becomes essential. “Sadly, over 99% of most native ash species won’t survive an infection, so treatment is necessary to keep your infected tree alive,” Andrew Conboy mentioned in his exclusive interview with Onions Australia. “If the infestation is caught early, before a significant portion of the tree dies, treatment can help maintain the tree’s health for some time.”
If more than half of the tree has perished, Conboy suggested that treatment might not be worthwhile. Moreover, even if you believe your tree has a fighting chance and decide to pursue treatment, there are drawbacks, such as the potential impact of insecticide on beneficial native insects also feeding on your ash. You’ll also need to commit to annual or biennial treatments to keep EAB at bay, representing a significant financial investment. Despite these efforts, “it is uncertain if treating the trees indefinitely is a sustainable practice,” Conboy remarked.
Treating your ash tree for pest infection
If you’ve decided to save your tree, Andrew Conboy recommended several effective treatments. “These include basal trunk injections with systemic insecticides, typically administered by a tree service or plant health care professional,” he exclusively informed Onions Australia. “Less commonly, you can perform a soil drench/injection with insecticides. These are usually applied annually or biennially, costing several hundred dollars per tree.”
With tens of millions of ash trees already decimated by the emerald ash borer, is it worthwhile to maintain an ash tree on your property that is currently thriving? Conboy believes it is, despite the unfortunate reality that many of them no longer reach great heights. However, many ash species continue to reach sexual maturity, allowing them to produce and spread seeds before becoming infected.
“I strongly encourage those with sufficient space to nurture any ash saplings on their property,” Conboy advised. “Even if they fall victim to the borer when they reach 5 or 6 inches in diameter, you will be contributing to preserving the local genetic diversity of these threatened ash species and helping scientists gain time to devise a potential solution.” In essence, don’t lose hope. Continue caring for and pruning your ash tree to keep it robust and healthy, and remain vigilant for signs of unwanted visitors. If you’re determined and patient, you might even try the popular method of propagating ash trees from seed.
