Pest description and crop damage Four species of inchworm may injure tree fruit or hazelnuts, three of which are native to North America. The fourth, and potentially most serious, is the European winter moth, which was introduced to the PNW in 1958. Adult males are gray or off-white moths which are present in late fall and winter, hence the name. Female moths are wingless. The larvae are pale green with a light stripe down their sides, up to 0.5 inch long. Larvae damage young hazelnut buds and leaves. Symptoms of leaf feeding are distinct from leafroller larvae: leaves are tied together with silken threads but not rolled and leaves appear tattered. In commercial orchards, this insect seldom is a pest.
Biology and life history Wingless females deposit 100 to 200 eggs on hazelnut stems or in crevices in bark in late fall and winter. Since the female cannot fly, populations of winter moth often are clumped, as all the eggs usually are deposited in one tree. The eggs hatch in early spring at the green tip stage, and larvae feed from then until petal fall. The larvae often drop on silken threads and are carried by the wind to new growth areas. They drop to the soil to pupate during the summer, and, after the first severe frost, the adults emerge. There is one generation per year.
Pest monitoring Check for larvae from March 15 to May 31, checking three terminals per tree and three leaf clusters per terminal. Each terminal is a sampling unit. Treat when infestation level is 20%.
General predators such as lacewings, assassin bugs, tachinid flies, and spiders feed on the larvae, although populations are not always well regulated by these predators. Temperature may play a bigger role in controlling populations.
Home orchardists: Pick larvae when you find them, and prune out infested growths.
Management-chemical control: HOME USE
No products registered on this host for this pest.
Management-chemical control: COMMERCIAL USE
- Bacillus thuringiensis var. kurstaki-See label for rates. PHI 0 days. Apply with spreader-sticker. Some formulations are OMRI-listed for organic use.
- carbaryl (Sevin XLR Plus) at 2 to 5 quarts/a. Other formulations are also available. PHI 14 days. REI 12 hr. Extremely toxic to aquatic invertebrates.
- chlorpyrifos- Generic labels for chlorpyrifos are also available.
- Lorsban 75 WG at 2 to 2.67 lb/a. PHI 14 days. REI 24 hr. Do not exceed three applications per season. Extremely toxic to fish. Toxic to birds and wildlife.
- Lorsban 4E at 3 to 4 pints/a. PHI 14 days. REI 24 hr. Do not exceed three applications per season. Extremely toxic to fish. Toxic to birds and wildlife.
- chlorpyrifos + gamma-cyhalothrin (Cobalt) at 6.5 to 14.2 oz/100 gal (26 to 57 fl oz/a). PHI 14 days. Do not make more than 3 applications per season of Cobalt or other product containing chlorpyrifos for hazelnuts.
- chlorpyrifos + O-diethyl-O-(3,5,6-trichloro-2-pyridinyal) phosphorothioate (Vesper, Vulcan) at 3 to 4 pints/a. PHI 14 days. REI 24 hr. Do not make more than 3 applications per season.
- diflubenzuron (Dimilin 2L) at 12 to 16 fl oz/a. PHI 28 days. REI 12 hr. Extremely toxic to aquatic invertebrates. Do not apply within 25 ft of bodies of water.
- diflubenzuron + lambda-cyhalothrin (DoubleTake) at 4 to 5 fl oz/a. PHI 28 day. REI 24 hr. Do not exceed 20 fl oz/a per growing season or 15 fl oz/a per year growing season post bloom. Extremely toxic to aquatic invertebrates. Do not apply within 25 ft of bodies of water, 150 ft if applied by air.