Operophtera brumata
Pest description and crop damage The European winter moth 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, possibly because management for other pests also control winter moth. Baited traps will consistently catch moths, but economic damage to orchards is relatively rare at this time.
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%. Commercial lures and traps are available and moths can be caught in high numbers. However, damage is not very common and apparently not highly corelated with the number of moths that are caught in traps.
Management-biological control
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.
Management-cultural control
Home orchardists: Pick larvae when you find them, and prune out infested leaves.
Management-chemical control: HOME USE
- emamectin benzoate
Management-chemical control: COMMERCIAL USE
- Bacillus thuringiensis var. kurstaki-See label for rates. PHI 0 days. Follow label instructions. Add a spreader-sticker to enhance control. 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.
- 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.
- emamectin benzoate (Proclaim) at 3.2 to 4.8 oz/A. PHI 14 days. REI 12 hr.
- fenpropathrin (Danitol 2.4 EC) at 10.3 to 21.3 oz/A (0.2 to 0.4 lb ai/A). PHI 3 days. REI 24 hr. At least 50 gal water for ground applications. Note buffer requirements for use near aquatic zones.
- GS-omega/kappa-Hxtx-Hv1a (Spear-Lep) at 1 to 2 pints/A. Biological insecticide that should be tank mixed with equal parts of Bt. PHI 0 day. REI 4 hr.
- spinosad (Entrust SC) at 4 to 10 oz/A (0.06 to 0.16 lb ai/A). PHI 1 days. REI 4 hr. OMRI-listed for organic use.