Last Fall as the sun started to go down a bit earlier, I noticed lots of these white-ish/gray moths gathering around my porch light. I didn’t think much of them as I figured the fast-approaching cold weather would kill them, and moved on to thinking about cleaning up fallen leaves and putting together holiday shopping lists. What I didn’t know then was that those little moths, frequently called “Winter Moths”, were laying little time bombs on my leafy trees. There was little I could do to then to control their damage come the Spring, but I’ve learned since then that there are ways to control winter moths, safely and with organic products.
While the moths themselves can be somewhat pesky and unattractive, the real problem is the Winter Moth Larva, which hatches in the Spring. While the larva (small green caterpillars/worms) look fairly cute and cuddly, they can do extensive damage to orchards and ornamental deciduous (leafy) trees as they eat newly growing leaves. Not only are crops lost, but the trees can be damaged extensively due to defoliation. Since Winter Moths are not native to North America, there are few natural controls (most natural predators are overwintering or dormant themselves).
Luckily for growers and homeowners, there are several treatments that are effective at Winter Moth Control, and even better, most are organic.
Winter Moth Control with Horticultural Oil – Winter Moth lay their eggs on leafy trees that their offspring will devour. Horticultural oil (such as Neem Oil or Bonide Horticultural Oil) can be sprayed on deciduous trees in the Spring, when temperatures are above freezing, but prior to leaves budding. The oil smothers the eggs, preventing an infestation before the larva hatch. This method works well for smaller trees and shrubs, while larger and taller trees may be more vulnerable to infestation.
Winter Moth Control with BtK – “Btk” (Bacillus thuringiensis kurstaki” is a bacteria that kills many types of moth larva (caterpillars, “inchworms”, cabbage loopers, etc). It is safe for humans and has been used for many years as an organic pesticide. Btk products such as Summit Caterpillar & Webworm Control can be applied once the larva has hatched and is actively eating leaves, usually in May and early June.
Winter Moth Control with Spinosad® – Spinosad is an insecticide that was derived from a bacteria discovered on a sugar plantation in the Virgin Islands. It is one of the few broad-spectrum insecticides that has been approved by the USDA for organic growing. It is safe for humans and pets, and effective for controlling moth larva and other insects that feed on fruit, vegetable, and nut crops. Similar to Btk, products with Spinosad, like Captain Jack’s Dead Bug Brew can be used once the moth larva make their appearance in the Spring.
So as your fruit trees and bushes and leafy trees are leafing out, and looking as if they are being chewed down, you probably have an infestation of Winter Moths. Spring and early summer is the time to stop them before they start their life cycle again, and luckily there are several safe and effective measures you can take to control Winter Moths, and stop growth and spread.
As with all pest control measures, we recommend asking the experts at the your local garden center to avoid damage to your plants or to the environment, or contact your local agricultural cooperative extension office for advice.