Gypsy Moth

Lymantria dispar

Gypsy moth, Lymantria dispar, is one of the most significant exotic pests in the history of the United States. Introduced to Boston in the 1860s, it continues to spread throughout the eastern United States and into the Midwest. Gypsy moth larvae defoliate trees leaving them weakened and vulnerable to secondary fungal and insect invaders. Gypsy moth will affect trees in natural settings, forest plantations, and urban environments, often defoliating thousands of trees in a single outbreak.

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Treatment Strategy

Heavy pressure from gypsy moth has the potential to cause mortalities on shade trees, especially in stressful urban sites where gypsy moth feeding is coupled with stress from abiotic factors. Healthy trees can tolerate a single gypsy moth defoliation event; however, multiple defoliation events can cause dieback and decline even on healthy trees.

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Gypsy Moth Treatment Option 1

Insecticide treatments on individual high value shade trees are the only way to ensure predictable protection during high pest pressure. Sprays with contact insecticides such as Carbaryl, Tengard®, or Up-Star® Gold are effective. However, with the advent of soil-applied systemics this practice has become outdated.

Application Type – Foliar spray

DIY Product/Equipment Needed:

• CarbarylTengard® or Up-Star® Gold

• Pump up tank sprayer with wand

• Gloves

• Safety glasses

Gypsy Moth Treatment Option 2

The active ingredient in Conserve® SC (spinosid) is a naturally occurring bacterium found in soil. Conserve® SC can be applied as a foliar spray and is considered non-toxic to people, yet is effective on moth and butterfly insects.  Sprays typically begin as small larvae are spotted and tiny shot holes begin appearing in the leaves.

Application Type – Foliar spray

DIY Product/Equipment Needed:

• Conserve® SC

• Pump up tank sprayer with wand

• Gloves

• Safety glasses

Gypsy Moth DIY Kit

Option 1 

Application Type – Foliar spray

DIY Product/Equipment Needed:

• CarbarylTengard® or Up-Star® Gold

• Pump up tank sprayer with wand

• Gloves

• Safety glasses

Option 2

Application Type – Foliar spray

DIY Product/Equipment Needed:

• Conserve® SC

• Pump up tank sprayer with wand

• Gloves

• Safety glasses

How Is It Spread?

• Eggs hatch in spring and larvae emerge.

• Young larvae begin to feed in April and May and continue through summer.

• Gypsy moth caterpillars pupate early to mid-summer.

• In summer, hair-covered egg masses are laid in crevices, under picnic tables, and on vehicles.

• The insect spends the winter in these egg masses.

• Gypsy moths have one generation per year.

Susceptible Trees

Gypsy moths are known to feed on hundreds of woody plant species. However, the preferred species include oak, aspen, willow, linden, hawthorn, apple and alder.

Symptoms

• Shot holes in leaves, beginning in spring, resulting in partial or complete defoliation by midsummer.

• White, 1 ½ inches long, webby egg masses on trunks and limbs.

• Young gyspy moth caterpillars are black with orange spots on their backs.

• Mature caterpillars grow up to 2 inches long and have five pairs of blue spots and six pairs of red spots in rows across their backs.

• Pupae are tear-drop shaped and brown.

Lookalikes

Eastern tent caterpillar, Forest tent caterpillar, Sawflies

Related/Similar Problems

Eastern tent caterpillar, Forest tent caterpillar, Sawflies

Timing

Spring-Early summer

Urgency

Moderate

Risk of Spreading

High

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