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 on or near nut clusters and larvae wander to the nuts and chew their way through the shell. Larvae feed within the nut and destroy the kernel. When fully developed, the larvae are whitish with a brown head capsule 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 under the husk, 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/micropyle can affect susceptibility of different hazelnut cultivars to this pest.
Biology and life history The insect is found in several wild and cultivated nuts in North America but is particularly common in acorns and hazelnuts in the Pacific Northwest. 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 1-2 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 8-10 days, and the tiny larvae search out nuts. They burrow into the nut, entering the shell through the micropyle, which is a pore and the thinnest part of the shell in the center of the basal scar. Larvae feed on the kernel for 2 to 4 weeks before they bore their way out of the shell as fully developed larvae. After a period of wandering, larvae form cocoons (hibernaculae) 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 trap captures. More selective sprays target the immature stages and will not shut down trap captures because they are less toxic to adult moths. The residue from such materials will continue to protect nuts from attack even as moths are caught in traps and are laying new eggs. Proper timing of spray applications is critical with selective materials with and those with lower residual activity. 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 Use of pheromone traps in combination with the degree day model is recommended for timing management. 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 nut clusters 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). Keep extra lures in the freezer (not in your vehicle), and replace lures and trap liners according to the recommendations of the manufacturer. The action threshold is 2 to 3 moths per trap, or 5 moths in any one trap. Apply insecticides 8-12 days after reaching the threshold in your orchard block to target larvae emerging from eggs prior to nut penetration, this should roughly correspond to 955 degree days (DD) since April 1 in the filbertworm degree day model, which is the point of first egg hatch. If the trap threshold is not reached, then sprays are not necessary. Use trap captures to check synchrony with the degree day model. Good degree day (DD) reference points that can be verified with traps are the earliest capture of moths (580 DD), the average first moth emergence (610 DD), the earliest peak moth emergence (1158 DD), the average peak moth emergence (1188 DD) and the latest peak moth emergence (1217 DD). Products with adulticidal/contact activity (kills adult moths) and long residuals can be applied after average first moth emergence but before first egg hatch (610-955 DD) if population is above threshold as indicated by trap captures. Products with ovicidal activity (kills eggs) can be applied between first egg laid and first egg hatch (815-955 DD). Products with larvicidal activity only should be applied just prior to first egg hatch (955 DD) to maximize strength of residue encountered by larvae. By 1533 DD, larvae will already be present in nuts if there is a population above the trap threshold. A second cover spray may be necessary in 2-3 weeks, or if moths continue to be caught in traps at rates above the threshold and the residual activity of the first application is expired. Moths flying late in the season can cause unexpected crop damage, so it is important to keep monitoring through nut drop. Note that the phenology model only covers the first generation, and the 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. Of the hazelnut cultivars currently planted, Yamhill was found to have the thinnest average shell at the micropyle. McDonald, Wepster, Sacajawea, and PollyO had very similar shell thickness at the micropyle but thicker than Yamhill. Lewis, Jefferson, Dorris, and Barcelona had the thickest shell at the micropyle.
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 are most conducive to mating disruption. 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 only.
- 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.
- 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.
- 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.
- 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.
- kaolin clay (Surround WP) at 50 to 75 lb/A. Suppression only, OMRI-listed for organic use. 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, generics) 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 to 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. OMRI-listed for organic use.
- 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.