Pest description and crop damage Filbertworm is the key pest of hazelnuts in the Pacific Northwest and a close relative of codling moth, one of the most economically important insects worldwide. Adult moths are gray to reddish with golden bands across each forewing. Female moths lay the eggs near nut clusters and larvae must locate the nuts and gain entry. Larvae feed within the nut and destroy the kernel. When fully developed, the larvae are whitish with a brown headcapsule and are approximately 0.5 inch long. The entry hole into the shell is not often seen, as the larvae gain entry into the kernel through the micropyle on the basal scar, but the much larger exit hole is apparent after the larvae has finished devouring the kernel. Research has shown that shell thickness at the basal scar can affect susceptibility of different hazelnut cultivars to this pest.
Biology and life history The insect is found in many wild and cultivated nuts in North America but is particularly common in acorns and hazelnuts. The filbertworm overwinters as a larva in a silken cocoon under leaves and debris on the ground or in cracks and crevices on trees. Some larvae also overwinter 1 to 2 inches beneath the soil surface. The larvae pupate in spring and the adults begin to emerge mid-June through October. After mating the female moths begin to lay single eggs near developing nuts. Eggs hatch in 8 to 10 days, and the tiny larvae search out nuts. They burrow into the nut to feed on the kernel for 2 to 4 weeks before they bore their way out as fully developed larvae. Most then form cocoons (hibernacula) to overwinter, although some may pupate and become moths within that season (i.e., multiple generations). Sprays are timed to target the eggs and the wandering larvae before they penetrate the nuts. Some materials will also kill adult moths and it is important to understand this when following trap captures. Only materials with adult activity (such as pyrethroids) will cause shutdown of pheromone traps. More selective sprays will not shut down trap captures. This is normal, and the residue from such materials will continue to protect nuts from attack. Proper timing of spray applications is critical when selecting materials with lower residual and when taking advantage of the ovicidal activity of some materials. Use the degree-day model with a weather station near the orchard or provide your own weather data from the orchard. This tool is available from the Integrated Plant Protection Center (IPPC): http://uspest.org/wea/ and at https://cropconnect.com/custom/OSU/.
Pest monitoring Filbertworm flight has been starting earlier in the season compared to historic norms. Previous recommendations were to start hanging pheromone traps before the flight of filbertworm moths begins in mid-June, but now it is clear that traps should be placed mid-May to capture the first moths. Note that early moth captures may not threaten the crop if the nuts have not yet developed. Use four traps for the first 10 acres and one for each additional 4 acres. Place the traps in the upper third of the canopy. Moth captures will not be representative if traps are not placed high in the canopy (pheromone is heavier than air). The action threshold is 2-3 moths per trap or five moths in any one trap. Apply insecticides 8-12 days after filbertworm moths emerge in your orchard block to target larvae emerging from eggs prior to nut penetration (first egg hatch occurs when 955 degree-days have accumulated after April 1). An earlier application with a long-residual material to target the adult moths can also be effective. A second application may be necessary in 2-3 weeks, or if moths continue to be caught in traps at rates above the threshold. Moths flying late in the season can cause unexpected late crop damage so it is important to keep monitoring through harvest. Note that the phenology model only covers the first generation and trap threshold approach should be used for late season management.
Predators and parasitic wasps likely assist in killing some larvae before they gain entry to the nuts. Some moths may also be killed by predators. Bats may capture moths on the wing during dawn and dusk flight periods. The activity of biological control will be affected by management tactics for other pests. For example, use of mating disruption against key pests has been shown to enhance biological control in orchards.
Hazelnut varieties are not equally susceptible to filbertworm. The thickness of the micropyle, which is the thinnest point of the shell on the basal scar of the nut determines susceptibility, as this is the point of entry for the newly hatched larvae into the nut. Hardness of the shell may not matter, and nuts can be attacked very late in the season. New hazelnut cultivars are still being tested for susceptibility to filbertworm.
First nut drop typically contains a higher percentage of nuts infested by filbertworm. Flailing or otherwise destroying these first nuts prior to harvest may reduce infestation levels. Flailing acorns from oaks near the orchard may also help reduce filbertworm pressure.
Isomate FBW Ring is a commercial mating disruption product. Apply a minimum 20 dispensers per acre (more may enhance the effect). Hang pheromone dispensers high in the canopy on lateral branches before initial moth flight. Continue to monitor traps and prepare to apply border sprays or supplemental cover sprays if traps continue to capture moths at rates above the threshold. Large, contiguous blocks under mating disruption are most effective. The continual release of pheromone from dispensers in the orchard interferes with the male moth's ability to locate females for mating within the orchard. Mated females originating from outside the orchard can still come in and lay eggs resulting in damaged nuts. Mating disruption technology is best applied to low to moderate filbertworm populations, so consider getting any problematic moth populations under control before utilizing mating disruption. Do not apply to home orchards, orchards with steep slopes, or orchards with a high edge to core ratio.
Management-chemical control: HOME USE
- acetamiprid-Do not apply until after trees have flowered or when bees are actively foraging. Do not make more than one application a year. PHI minimum of 7 days.
- azadirachtin (as a mix with other ingredientsl)-Some formulations are OMRI-listed for organic use.
- kaolin clay-Some formulations are OMRI-listed for organic use. (suppression)
- lambda-cyhalothrin (as a mix with other ingredients).
- spinosad-Some formulations are OMRI-listed for organic use.
Management-chemical control: COMMERCIAL USE
Filbertworm emergence notices are sent to growers. These can serve as a rough guide for approximate spray timings. Pheromone trapping and use of the degree-day phenology model should be used to optimize spray timing and efficacy.
- alpha-cypermethrin (Fastac CS) at 3.2 to 3.8 fl oz/a. PHI 7 days. REI 12 hr. Do not exceed 11.4 fl oz/a per season. Highly toxic to bees, extremely toxic to fish and aquatic invertebrates. Do not apply within 25 feet of aquatic habitats, or with 150 ft if aerial application. Apply as indicated by scouting.
- acetamiprid (Assail 70WP) at 0.57 to 1 oz/100 gal water (2.3 to 4.1 oz/a). PHI 14 days. No more than 4 applications per season.
- beta-cyfluthrin (Bathyroid) at 2 to 2.4 oz/a. PHI 14 days. REI 12 hr.
- Brigade WSB at 0.05 to 0.2 lb ai/a. PHI 7 days. REI 12 hr. Do not graze livestock on treated cover crops. Highly toxic to bees and toxic to fish and aquatic invertebrates.
- Fanfare EC at 3.2 to 12.8 fl oz/a. PHI 7 days. Do not graze livestock on treated cover crops. Highly toxic to bees and toxic to fish and aquatic invertebrates.
- carbaryl (Sevin XLR Plus or its equivalent in another formulation) at 0.5 to 1.25 quarts/100 gal water (2 to 5 quarts/a). PHI 14 days. REI 12 hr. May cause rapid increase of aphid populations 3 to 4 weeks after application. Extremely toxic to aquatic invertebrates.
- chlorpyrifos- Generic labels for chlorpyrifos are also available.
- Lorsban Advanced at 3 to 4 pints/100 gal. PHI 14 days. REI 1 day. No more than three applications per season. Do not graze livestock in the treated area. Extremely toxic to fish. Toxic to birds and wildlife. RESTRICTED USE IN OREGON.
- 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. RESTRICTED USE IN OREGON.
- chlorantraniliprole (Altacor) at 3 to 4.5 oz/a. PHI 10 days. REI 4 hr.
- cyfluthrin (Baythroid XL) at 2 to 2.4 oz/a. PHI 14 days. REI 12 hr.
- 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.
- esfenvalerate (Asana XL) at 8 to 12 fl oz/100 gal water (10 to 18 fl oz/a). PHI 21 days. REI 12 hr. Do not apply more than 0.2 lb ai/a per season. Extremely toxic to fish and aquatic habitat.
- fenpropathrin (Danitol 2.4 EC) at 10.3 to 21.3 oz/a. PHI 3 days. REI 24 hr. At least 50 gal water for ground applications. Note buffer requirements for use near aquatic zones.
- flubendiamide + buprofezin (Tourismo) 10 to 14 fl oz/a in a minimum of 100 gal water. Do not apply as alternate row middle (ARM) sprays; full cover sprays only. PHI 60 days. REI 12 hr.
- kaolin clay (Surround WP) at 50 to 75 lb/a. Suppression only. PHI 0 days. REI 4 hr.
- Warrior II/ Grizzly Too at 1.28 to 2.56 fl oz/a. PHI 14 days. REI 24 hr. Do not exceed 0.16 lb ai/a per season or 0.12 lb ai post bloom.
- LambdaStar/ Drexel L-C at 2.56 to 5.12 fl oz/a. PHI 14 days. REI 24 hr. Do not exceed 0.16 lb ai/a per season or 0.12 lb ai post bloom.
- methoxyfenozide (Intrepid 2F, Troubadour 2F) at 8 to 16 fl oz/a. PHI 14 days. REI 4 hr. Apply when egg hatch begins. Reapply at 14 to 21 day intervals under high pressure or sustained moth flight. Do not exceed 24 fl oz/a per application or 64 fl oz/a (1 lb ai/a) per season. Do not apply within 25 ft of an aquatic habitat, 150 ft if applied by air.
- methoxyfenozide + spinetoram (Intrepid Edge) at 6-12 oz/a. Apply at initiation of egg hatch, if necessary reapply after 14-21 days, but not before 14 days. PHI 7 days. REI 4 hr. No more than 12 fl oz/a/season.
- Ambush 25W at 12.8 to 25.6 oz/a. PHI 14 days. Do not graze treated orchards. Extremely toxic to fish and aquatic habitat.
- Ambush 2E at 0.8 to 1.6 pints/a. PHI 14 days. REI 12 hr. Do not graze treated orchards. Extremely toxic to fish and aquatic habitat.
- Pounce 3.2 EC at 0.5 to 1 pint/a. PHI 14 days. REI 12 hr. Do not graze treated orchards. Extremely toxic to fish and aquatic habitat.
- PermaStar AG at 8 to 16 oz/a. PHI 14 days. REI 12 hr. Highly toxic to bees, toxic to fish and aquatic invertebrates.
- pyriproxyfen (Esteem 35 WP ) at 3.2 to 4 oz/100 gal water (13 to 16 oz/a). Do not apply more than twice per season. PHI 21 day. REI 12 hr.
- spinetoram (Delegate WG) at 1.5 to 1.75 oz/100 gal water (4.5 to 7 oz/a). PHI 14 days. Apply no less than one week apart, with a maximum 4 applications per season.
- spinosad (Entrust SC) at 4 to 10 oz/a. PHI 1 days. REI 4 hr. OMRI-listed for organic use.
- spinosad (Success Naturalyte) at 4 to 10 oz/a in 100 gal water. PHI 1 days. REI 4 hr. Do not exceed 29 oz/a per season.
- tebufenozide (Confirm 2F) at up to 30 oz/a. PHI 14 days. REI 12 hr. Apply when egg hatch begins. Do not exceed 30 oz/a per application or 122 oz/a for the season.