Blueberry-Cherry fruitworm

Grapholitha packardi

Pest description and crop damage In the PNW, cherry fruitworm has been found infesting blueberries only in parts of western Washington. Adults are small, dark gray/brownish moths with a wingspan of about 9-10 mm. They are active mostly at night and so are rarely seen. Larvae have pink-red bodies with brown or black heads. Newly hatched larvae tunnel into fruit. One larva can easily destroy an entire cluster of berries.

Biology and life history The fruitworm overwinters as a mature larva, hibernating in cavities in dead wood on the bush, or in pruning stubs. As temperatures warm, the larva changes into a pupa, and, about 2 weeks later, the adult emerges in late spring. A few days after emergence, mating and egg deposition occur. Females lay opaque, green-white flattened eggs on the underside of leaves at the time of blossom drop, as well as on developing small green fruit. After eggs hatch, larvae penetrate the berry and begin feeding on the fruit pulp. There is only one generation per year.

Scouting Visual inspection for eggs should begin at petal fall/early fruit set and when adult flight has started. Eggs are opaque and difficult to see; look carefully on the underside of leaves and on small green berries. Larval infestations may be difficult to detect early in the season because there is little external evidence of the insect's presence. Look for a pin-sized entry hole near the stem of any small, shrunken berries that have turned prematurely blue, and then open adjacent berries to find the larvae.

Management-cultural control

Remove overwintering environments for larvae, such as weeds, prunings, and trash around the plants. Also, if possible, manage alternate hosts (e.g. cherry, apple, rose) on field borders.

Home gardeners: Larvae and eggs can be hand-picked if found.

Management-chemical control: HOME USE

Because this is a fruit pest, and because egg laying and hatch occur at bloom and petal fall, great care must be taken if applying pesticides to avoid bee injury with any of the following products. Apply after petal fall, or at night.

  • carbaryl
  • pyrethrins-Some formulations are OMRI-listed for organic use.
  • spinosad-Some formulations are OMRI-listed for organic use.
  • zeta-cypermethrin-Toxic to bees; do not apply when bees are foraging.

Management-chemical control: COMMERCIAL USE

Apply insecticides when larvae are small, usually at petal fall.

  • acetamiprid (Assail) at 0.085 to 0.1 lb ai/a. PHI 1 day. Do not exceed 0.5 lb ai/a per season.
  • Bacillus thuringiensis (Bt) (several brands)-Consult label for rate. PHI 0 days. A spreader-sticker increases efficacy. OMRI-listed for organic use.
  • carbaryl (Sevin and other brands) at 1.5 to 2 lb ai/a. PHI 7 days. Latex-based formulations such as Sevin XLR Plus are less hazardous to bees. Do not apply to bloom.
  • chlorantraniliprole (Altacor) at 0.066 to 0.099 lb ai/a. PHI 1 day.
  • cyantraniliprole (Exirel) at 0.065 to 0.088 lb ai/a. PHI 3 days. Do not apply when bees are foraging. Note "Bee Advisory Box" and restrictions on the label.
  • diazinon (several brands) at 0.5 lb ai/a. PHI 7 days. Do not apply to bloom. One application per season allowed; as such, consider other pests that may need to be managed with diazinon. Restricted use pesticide.
  • fenpropathrin (Danitol) at 0.2 to 0.3 lb ai/a. PHI 3 days. Do not exceed two applications per season.
  • indoxacarb (Avaunt) at 0.065 to 0.11 lb ai/a. PHI 7 days.
  • malathion (several brands) at 1 lb ai/a. PHI 1 day. Apply only during late evening to avoid bee poisoning.
  • methomyl (Lannate) at 0.45 to 0.9 lb ai/a. PHI 3 days. Do not apply during bloom. Apply as spray in 100 gal water/a at blossom drop and again two weeks later. Cover foliage thoroughly. Restricted use pesticide.
  • methoxyfenozide (Intrepid 2F) at 0.16 to 0.25 lb ai/a. PHI 7 days. Apply when egg laying begins and again at 100% petal fall (usually 7 to 14 days after first application). Additional applications at 10- to 14-day intervals may be required under high population pressure or sustained moth flights.
  • spinetoram (Delegate WG) at 0.05 to 0.09 lb ai/a. PHI 3 days. SLN 24c OR-170016 for Delegate allows a 1-day PHI in Oregon only; read label carefully for restrictions on number of applications allowed. Toxic to bees for three hours following treatment. Do not apply when bees are foraging.
  • spinosad (Entrust) at 0.062 to 0.1 lb ai/a. PHI 3 days. SLN 24c OR-160013 and WA-140014 for Entrust SC formulation allow a 1-day PHI in Washington and Oregon only. Target eggs at hatch or small larvae. Toxic to bees for three hours following treatment. Do not apply when bees are foraging. Entrust is OMRI-listed for organic use.
  • tebufenozide (Confirm 2F) at 0.25 lb ai/a. PHI 14 days. Apply when egg laying begins and again at 100% petal fall (usually 7 to 14 days after first application). Additional applications at 10- to 14-day intervals may be required under high population pressure or sustained moth flights. Do not exceed 64 fl oz/a product per crop season.