Flea beetle

Flea beetles are tiny, jumping beetles that chew small, round holes in alder and other foliage, creating a shothole pattern. You will see adults jumping when you disturb plants. Damage appears in spring on new growth and continues through early summer. Though numerous holes appear, most trees tolerate feeding without serious decline, though seedlings can be severely affected.

Protect young seedlings with floating row covers or fine netting until plants are established and can tolerate leaf damage. Spray insecticidal soap or neem oil targeting adults in spring to reduce populations. Encourage natural predators including parasitoid wasps and tachinid flies. Most established trees tolerate flea beetle damage well without treatment. Avoid over-fertilizing with nitrogen, which promotes tender new growth preferred by beetles.