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Notes on Blueberry Insects
Cranberry and cherry fruitworm

Author: OMAFRA Staff
Creation Date: 17 May 2006
Last Reviewed: 17 May 2006

 

Identification

Larvae of these moths feed on developing fruit. Cranberry fruitworm is the major pest in most areas. See Table 1 - Distinguishing Cranberry and Cherry Fruitworm.

Table 1: Distinguishing Cranberry and Cherry Fruitworm
  Cranberry Fruitworm Cherry Fruitworm
Scientific name
 Acrobasis vaccinii Grapholita packardi
Adult
 A pyralid moth, with the typical pointed head and v-shape. Moths have a wingspan of about 15 mm, greyish brown with white markings. A tortricid moth, with a typical bell-shape. Moths are mottled grey/black with forewings about 5mm and wingspan of about 9.5 mm
Larva
 Greenish caterpillar with brownish red tinges on back, about 9.5 mm long when mature. White or orange/pink caterpillar, with brown head.
Damage
 One larva ties clusters of three to six fruit together with silk and causes damage to several berries. Messy feeding sites, with external sawdust-like frass and webbing, are characteristic of damaged fruit. One larva damages one or two fruit. Berries are filled with frass, but damage is internal and frass is not visible from outside.

Cranberry fruitworm

Cranberry fruitworm

Period of activity

Both pests have a similar life cycle. Adults are active in spring and during bloom. Eggs are laid in the calyx of developing small green fruit. There is one generation per year.

Monitoring and thresholds

Pheromone lures are available for each pest. See Pest Monitoring Equipment Suppliers on the OMAFRA website. Use separate traps and lures for each pest or monitor for the predominant species, usually cranberry fruitworm.

  • Use pheromone with Pherecon IC wing traps. Set traps out around mid-bloom. Use three traps for 4 ha (10 acres). Hang traps from the outside branches but not above the bush. Check traps twice weekly and record the number of moths trapped on a chart.

Management notes

Insecticides to control these pests should be applied around petal fall and again 10-14 days later. For cranberry fruitworm, you can use pheromone traps to time sprays more accurately.

Timing depends on the product applied.

When using Sevin or Malathion, which kill larvae on contact, apply five to seven days after cranberry fruitworm trap catches peak. A second insecticide is required if trap catches remain elevated seven days after application.

When you use the biological insecticide Dipel, spray at peak trap catch and continue at three to seven day intervals, to a maximum of four applications. Dipel must be ingested by larvae to be effective and works best when temperatures are warm because the larvae are more active. Dipel is unstable in bright sunlight, so apply on a cloudy day or in the evening. Dipel will reduce damage from cranberry and cherry fruit worm compared to unsprayed plots but control is usually less than that provided by other insecticides listed for control of these pests.

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