Hazelnut-Filbertworm

Cydia latiferreana

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 of scales across each forewing. Female moths lay the eggs on the upper surface of leaves. Early damage to developing nut clusters before the nuts are big enough to physically infest can result in aborted nuts and loss of whole clusters. However, the major concern is infestation of nuts, which is a major cause for dockage from nut processors. Larvae infest nuts and destroy the kernel, leaving only frass and mold behind. When fully developed, the larvae are whitish with a brown or black head capsule and are approximately 0.5 inch long. Research has shown that shell thickness at the basal scar/micropyle can affect susceptibility of different hazelnut cultivars to this pest. Trees are attacked by moths up to and beyond harvest, but nut susceptibility to attack by larvae can decline as shells fully harden. Note that hazelnuts ripen unevenly, and that a mostly mature nut crop will probably contain some greener nuts that remain susceptible.

Biology and life history This torticid moth is associated with several wild and cultivated fruits and nuts (see Chestnuts-Filbertworm) in North America, but is particularly common in acorns and chinkapin (Castanopsis chrysophyla) in the Pacific Northwest. In California, filbertworm can be a pest in commercial pomegranate crops. This pest rapidly adapted to attack European hazelnuts soon after the first orchards were planted in Oregon, and by the 1940s, it was the key pest. The filbertworm overwinters as a mature larva in a silken cocoon (hibernaculum) under leaves and debris on the orchard floor or 1 to 2 inches beneath the soil surface. Larvae also exploit cracks and crevices in the tree trunks. The larvae pupate in spring, and the adults begin to emerge and are first captured in late May with flight continuing through October. After mating, the female moths begin to lay individual eggs on leaves. Eggs hatch after several days, and the tiny larvae search out nut clusters. The first larvae attack developing clusters and later larvae burrow into the nuts, entering the shell through the micropyle, the pore in the center of the basal scar. Larvae feed on the kernel for 2 to 4 weeks. Mature larvae typically chew a larger exit hole out of the nut through the side wall of the shell. Larvae develop through what is thought to be 5 instars or stages.

There are two generations per year. The earliest developing larvae pupate and emerge as moths within the same growing season. Failure to control these early larvae can lead to increased pressure in the orchard later in the season. However, most larvae go into diapause (hibernation) after emerging from the nut.

Pest monitoring Use of pheromone traps is recommended for monitoring and timing cover sprays. Large plastic delta traps (LPD) are standard, but wing traps are also acceptable. Orange LPD traps will avoid capturing bees compared to white traps. 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). For tall trees rig a line over a branch to hoist the trap, or affix a long pole (like bamboo) to the trap to hoist it into the canopy. Make sure the entrance to the trap is clear of foliage. Keep extra lures in the refrigerator or freezer (never in your vehicle), and replace lures according to the recommendations of the manufacturer (usually 2 to 3 week intervals for septa). Trap liners don't catch moths efficiently when they are covered with debris and moth scales, so they need to be changed frequently. Camera and other smart trap technology are great to reduce time spend checking traps but even smart traps need to have lures and trap liners renewed periodically.

Filbertworm flight has been starting earlier in the season compared to historic norms. Historically, recommendations were to start hanging pheromone traps before the flight of filbertworm moths began in mid-June and first cover spray was typically applied in early July. Recent research indicates that traps should be placed by mid-late May. Moths are flying as soon as late May in some orchards, and are typically starting to fly in early June for most. Early moth captures should not be ignored because the nut clusters have not yet developed. Research indicates that the first moths attack the tree and larvae cause external vegetative damage to developing nut clusters resulting in aborted nuts. These early larvae represent the second generation because some of them will pupate and develop into moths that emerge later in the same growing season. Thus, they increase pest pressure in the orchard later in the growing season if not controlled.

The trap threshold method of timing sprays can be useful, but it is based on a high density of traps that few growers are willing to implement. The threshold method recommends 4 traps for the first 10 acres (or 1 trap per 2.5 acre) and 1 trap for each additional 4 acres. Lower densities of traps can be used successfully, but this will increase the likelihood of going over the threshold because as the distance between traps increases, moths are more likely to converge on the same trap. The action threshold is an average of 2 to 3 moths per trap per week, or 5 moths in any one trap. Apply selective larvicidal insecticides after reaching the threshold in your orchard block to target larvae emerging from eggs and wandering on the tree. There is a delay after going over threshold reflecting the time required for moths to mate and for females to mature fertilized eggs and for eggs to begin hatching. Products with long residuals can be applied soon after trap captures go above threshold. Products with ovicidal activity (kills eggs) can be applied several days after going over the threshold because ovicides are most active when eggs are laid on top of residues. However, oils can be applied over the top of eggs to smother them and these should be applied prior to egg hatch after threshold is reached. A second cover spray may be necessary in 2-3 weeks, or later in the season 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 do not cause as much crop damage as nuts mature. An important use of the trap threshold method is determining when not to spray. If there are adequate traps and the threshold is not reached, then sprays are not necessary.

Some insecticides will 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 reduce trap captures because they are less toxic to adult moths. However, 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 and those with lower residual activity.

Management-biological control

Predators and parasitic wasps help by killing eggs and larvae before they cause damage. Trichogramma minutum is an egg parasitoid that attacks eggs of filbertworm and is produced by commercial insectaries. In order to implement supplemental biological control with Trichogramma, it is important to verify emergence of wasps from their container and make sure that the timing is aligned so that wasps are deployed at the same time filbertworm eggs are present in the orchard. Some moths are killed by predators such as bats. Bats capture moths on the wing during dawn and dusk flight periods. The activity of biological control from insect natural enemies will be affected by management tactics for other pests. For example, reliance on mating disruption against key pests has been shown to enhance biological control in orchards because it can reduce insecticide use.

Management-cultural control

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 can also affect susceptibility later 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. Late cultivars may prolong the susceptibility to filbertworm.

First nut drop typically contains a higher percentage of nuts infested by filbertworm. Flailing these first nuts prior to harvest may reduce infestation levels. Flailing acorns from oaks near the orchard may also help reduce filbertworm pressure. Some growers have had success running pigs through their orchard or adjacent oak groves after harvest to feed on fallen, larvae-infested nuts.

Management-behavioral control

Isomate FBW Ring is a commercial mating disruption product. The label rate is 20 to 40 dispensers per acre (higher rates increase pheromone point sources and 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 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 against 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

• azadirachtin (as a mix with other ingredients)(Azera)-Some formulations are OMRI-listed for organic use.
• boscalid (often as a mix with other ingredient) (Bonide Fruit Tree & Plant Guard)
• carbaryl (GardenTech Sevin)
• esfenvalerate (Monterey Bug Buster II)
• gamma cyhalothrin (Spectracide).
• spinosad-Some formulations are OMRI-listed for organic use.
• zeta-cypermethrin (GardenTech Sevin)

Management-chemical control: COMMERCIAL USE

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 reduce trap captures because they are less toxic to adult moths. However, 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 and those with lower residual activity.

Organic:

• azadirachtin + pyrethrins (Azera; see also Azera Pro) at 16 oz/30-100 gal water. PHI 0 days. REI 12 hr. Do not wet plants to the point of runoff.
• Bacillus thuringiensis var. kurstaki-See label for rates. PHI 0 days. Apply with spreader-sticker. Some formulations are OMRI-listed for organic use. Bt can be a good choice for the first cover spray when targeting early larvae prior to the development of infestable nuts. Can be a good choice for early moth flights when nuts are not yet developed enough for larvae to enter.
• Burkholderia spp. (Venerate XC) at 2 to 4 quarts/A in 50 to 100 gal water (coverage important). PHI 0 days, REI 4 hr.
• Chromobacterium subtsugae (Grandevo) at 1 to 3 lb/A in a minimum of 10 gal water. Moderate to low pest pressure only. PHI 0 days, REI 4 hr.
• Cydia pomonella granulosis virus (CpGV CP-4) (Virosoft CP4) at 1.6-3.2 oz/A in 100 gal water. Good coverage is critical at the point of egg hatch, reapply in 7 to 10 days. REI 4 hr.
• kaolin-Particle film. Some formulations are OMRI-listed for organic use. Can be a deterrent for filbertworm.
• spinosyns-note new generics (Kibosh SC, Estero SC, Spliven)
  • 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.
  • spinosad (Success Naturalyte) at 4 to 10 oz/A in 100 gal water (0.06 to 0.16 lb ai/A). PHI 1 days. REI 4 hr. Do not exceed 29 oz/A per season. OMRI-listed for organic use.

Conventional:

• acetamiprid (Assail 70WP) at 0.57 to 1 oz/100 gal water (2.3 to 4.1 oz/A) (0.10 to 0.18 lb ai/A). PHI 14 days. No more than 4 applications per season.
• alpha-cypermethrin (Fastac CS) at 3.2 to 3.8 fl oz/A (0.021 to 0.025 lb ia/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.
• beta-cyfluthrin (Bathyroid) at 2 to 2.4 oz/A (0.016 to 0.019 lb ai/A). PHI 14 days. REI 12 hr.
• bifenthrin-
  • 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 (0.05 to 0.20 lb ai/A). PHI 7 days. Do not graze livestock on treated cover crops. Highly toxic to bees and toxic to fish and aquatic invertebrates. WA only.
• carbaryl (Sevin XLR Plus or its equivalent in another formulation)-See label for specific formulations as some concentrations vary. Seven XLR plus 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 2.5 to 4.5 oz/A (0.055 to 0.99 lb ai/A). PHI 10 days. REI 4 hr. Make initial application just before or at filbertworm egg hatch. Depending on the length of the filbertworm moth flight, multiple applications may be required to protect the crop. Under heavy filbertworm pressure, apply on a 14-day retreatment interval. With low to moderate filbertworm pressure, apply on a 21-day interval.
  • Vantacor at 1.4 to 2.5 oz/A. Make no more than 4 applications per year and do not reapply within 7 days. PHI 10 days. REI 4 hr.
• cyfluthrin (Baythroid XL) at 2 to 2.4 oz/A (0.016 to 0.019 lb ai/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 7.3 to 12.8 fl oz/100 gal water (9.6 to 19.2 fl oz/A or 0.05 to 0.1 lb ai/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 (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.
• 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. A unique peptide-based insecticide that should be tank mixed with equal parts of Bacillus thuringiensis var. kurstaki. PHI 0 day. REI 4 hr.
• lambda-cyhalothrin-
  • Warrior II/ Grizzly Too at 1.28 to 2.56 fl oz/A (0.02 to 0.04 lb ai/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.
• permethrin-
  • 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.
• 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.