Over the past few years, Charlotte’s cankerworm infestation has continued to rise, despite all of the city-sponsored tree-banding. Local entomologists think this may due to a decrease in migratory birds, and lower ground beetles numbers from over-manicured lawns.
Although cankerworms usually don’t kill trees, they do eat plenty of leaves, which can weaken trees and make them more vulnerable to drought, other insects, and disease.
The first defense is to band trees in the fall to prevent cankerworms from traveling to the top to lay eggs. This includes small trees and even shrubs, which are overlooked by Charlotte’s grant-sponsored program, as well as by most homeowners.
The second, more aggressive defense against the leave-eaters is really more of an offense – spraying. One of the safest and more benign pesticides is Bacillus thurigensis or Bt. This product is sold under various brand names including Safer or Thuricide. It will cause a bacterial disease to develop only in moths and butterflies. This pesticide is legal for organic food production and has been used for decades with no known adverse effects on humans, wildlife, pets, fish, or honey bees. This pesticide is best used when insects are small to give them time to get sick and die – you won’t see immediate results.
If Charlotte’s canopy does not start to see decreased cankerworm populations, they may once again resort to aerial spraying, as they did in 1992, 1998 and 2008 – which proved to be very effective in reducing the population for several years.