WEST LAFAYETTE, Ind. - Homeowners who want to protect their ash trees from the destructive emerald ash borer should have trees treated no later than mid-May, a Purdue Extension entomologist says.
Adult borers soon will emerge from ash trees and begin feeding on them and laying eggs, so it is best to apply insecticide treatments to ash trees before this occurs, Cliff Sadof said. "This ensures that beetles are killed before they have a chance to lay eggs on the trees," he said. Sadof expects to see EAB adults emerging by the end of May.
The invasive beetle, which has been confirmed in all Indiana counties except 12 in the southeastern portion of the state, is almost always lethal to untreated ash trees.
The most extensive damage in Indiana has occurred in the northeast, where more than 14,000 dead and dying ash trees have been removed in Fort Wayne alone.
Communities on Indianapolis' north side have also lost thousands of ash trees to the EAB. In some of the most-affected areas, streets have had to be closed so that afflicted trees could be removed for public safety.
Sadof said it's not too late to save healthy trees. "Proper insecticide treatments can save trees, so more people are choosing this option," he said. "The catch is that you have to do it before the trees start looking too bad."
Infested ash trees have several visible symptoms, including a thinning of leaves in the upper third of the canopy. Woodpecker holes or splits in the bark that reveal the curvy trails left by the tree-chewing insect also indicate infestation. Because the beetles first attack tree tops, the D-shaped holes the borer makes when it exits the tree are often too high up to see until the tree is nearly dead.
Sadof says using insecticides to save trees can be less expensive than removing and replacing them.
Annemarie Nagle, exotic forest pest outreach coordinator for Purdue's Department of Entomology, heads a Purdue Extension program called Neighbors Against Bag Bugs to help neighborhoods work together to lower tree management costs.
"More communities are discovering that homeowners associations or just neighbors joining forces can save money," Nagle said. "Many tree care companies are willing to offer discounts for bulk work; neighborhoods end up saving a good portion of their trees."
Information on identifying infested trees, treatment and advice on hiring a professional arborist, plus a cost calculator are available on the Purdue website.