That Moth You’re Seeing May Be Winter Moth, and Your Hardwoods Could Be in Danger

Winter Moth

Have you noticed suspicious moths fluttering around, though the weather is getting colder and we’re heading into winter? They could be Winter Moth (Operophtera brumata), and the hardwood trees in your landscape may be in danger. Make sure infestation doesn’t take its toll next year by planning your early spring treatment now.


The Origin of Winter Moth

Winter Moth was introduced to North America from Europe and the Near East sometime in the 1930s. This invasive pest causes severe defoliation of hardwood trees, and as its name suggests, adult moths are generally active between November and January. Larvae begin feeding early on developing leaves. In cases of severe infestation, trees will have noticeable defoliation. In June, they drop to the ground to pupate in the soil until fall.

Early detection of Winter Moth is difficult as the first instar larvae begin feeding while the pre-formed leaf is still in the bud. First symptoms are only visible after these buds break and the leaves unfurl to reveal small feeding holes. Over the early weeks of the spring, this feeding damage becomes more apparent, and caterpillars may grow to a visible size. They may also descend from the canopy on silken threads.

Research shows that four consecutive years of defoliation can ultimately lead to tree mortality, so it is vital to protect hardwood trees from Winter Moth before it’s too late.


Treatment Options

For treatment of Winter Moth, we recommend a well-timed injection in early spring (before buds break) of TREE-äge®, TREE-age G4, or ACE-jet using either the TREE I.V. or QUIK-jet. TREE-äge can be applied for longer residual control (up to two years). ACE-jet (protects canopy for 3-5 weeks) should be applied when the larvae are actively feeding.

Generally, the best seasons for injection are fall and spring while trees are transpiring. The environmental conditions that favor uptake are adequate soil moisture and relatively high humidity, and the soil temperature should be above 40 degrees F. Hot weather or dry soil conditions will result in a reduced rate of uptake, so trees should be watered if applications occur when soil is extremely dry. Tree health will also affect treatment efficacy, so assess tree health prior to treating. For example, a declining tree (>50% canopy dieback) is a poor candidate for treatment.

After treatment, Winter Moth leaf feeding stops and the caterpillars will die. ACE-jet trunk injection in the spring will act very quickly and caterpillars will die rapidly. Monitor trees annually to determine the need for a repeat treatment.

TREE-äge may work more slowly through the tree’s vascular system but will have a longer residual protection time than ACE-jet, making it ideal for multi-season protection. You will still want to monitor the tree’s overall health to see if reapplication is necessary.

Don’t let Winter Moth get you down this season! Connect with us today to start planning your early spring treatment for next year now. Remember, proactivity is key to saving trees!