Control of Cranberry and Cherry Fruitworm in Highbush Blueberries

Cranberry and cherry fruitworm are the most common fruit-infesting insect pests of blueberries in Ontario, causing crop loss of 50% or more. Cranberry fruitworm is the more common pest of the two.

Both insects have a similar life cycle, and pest control products directed at the dominant species will also suppress the other. The easiest way to distinguish between these pests is by the damage they cause.

Figure 1: Cluster of blueberries damaged by cranberry fruitworm.

Figure 2: Cranberry fruitworm moth trapped on a sticky trap.

Life cycle:

Both insects have one generation per year.

Cranberry fruitworm overwinters as a fully grown larva in a cocoon made of silk and soil particles, under weeds and soil debris near the soil surface. Larvae pupate in the spring and moths emerge from bloom to fruit set. The adults are small, night flying insects with dark grey brown wings marked with white patches. Eggs are small, flat, roundish and translucent, laid on the developing small green fruit, generally at the calyx end. Eggs hatch in about 5 days. Larvae move to the stem end of the fruit, enter the fruit and feed inside the berry. Mature larvae drop to the ground, spin a cocoon and hibernate.

Cherry fruitworm overwinter as mature larvae under loose bark. In late spring they pupate and moths emerge. Eggs are laid on or near developing fruit around petal fall. Larvae tunnel into the calyx end of the fruit.

Monitoring:

Where cranberry fruitworm is the predominant pest, use pheromone traps to monitor for cranberry fruitworm moths. Pheromone can be purchased from several suppliers, see Pest Monitoring Equipment Suppliers on the OMAFRA website.

The pheromone for cranberry fruitworm is species specific and will not attract cherry fruitworm. If cherry fruitworm is the major pest at your site, purchase pheromone for cherry fruitworm. Use separate traps for each species, labeling the traps carefully.

Use the pheromone with Pherecon IC wing traps, because these will catch more moths than the Pherecon II traps used for orchard pests. Set the traps out around mid-bloom. Use at least 3 traps for 4 ha (10 acres). Hang the traps from outside branches, but not above the bush. Check traps twice weekly, remove moths with a twig or spatula, and record the number of moths trapped on a chart.

Figure 3: An example of recorded trap catches is shown in this graph.

Text equivalent of this graph

Control:

Currently registered products are listed in Table 2, and in OMAFRA Publication #360, Fruit Production Recommendations.

Sprays to control these pests are directed at the young larvae. Insecticide applications should begin at petal fall and continue to provide coverage for 3-4 weeks, while moths are active. When using Malathion or Sevin, re-apply 7-10 days after the first application. Residual activity of Dipel is much shorter compared to these products, so re-application is needed more frequently.

Pheromone traps can be used to time the insecticide application more accurately.

• For Malathion and Sevin, the first insecticide can be applied 5-7 days after trap catches peak. A second insecticide is only required if trap catches remain elevated 7 days after application.
• For Dipel, initiate spray applications at peak trap catch, and continue at 3-7 day intervals, to a maximum of 4 applications. Dipel is unstable in bright sunlight, so for maximum effectiveness, apply it on a cloudy day or in the evening.

Dipel applications will result in reduced damage from cranberry and cherry fruit worm, compared to unsprayed plots. However, because of the extended activity of cranberry and cherry fruitworm moths, and the short residual activity of Dipel, control will likely be inferior to that provided by other insecticides registered for control of these pests.

Related Links

• Pest Monitoring Equipment Suppliers, OMAFRA website
• OMAFRA Publication #360, Fruit Production Recommendations
• Fruitworm identification in blueberries, Michigan State University (disclaimer)
• Cranberry Fruitworm, Michigan University Extension

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