Northwest berry Foundation

Management Detail

Cherry Fruitworm

in Blueberries

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Latin name: Grapholita packardi Z.

Description:

Reason for Concern:
While a rare pest in most regions, Cherry fruitworm larvae have been reported to cause crop loss of 50% or more.

Identification/Symptoms:
The adult is a small, dark gray bell-shaped moth with brown bands on the wings. Wingspan is about 3/8-inch. The larva is a white or orange/pink caterpillar about 8 mm long with a brown head. . The pupa is golden brown and about 6 mm long. Eggs are flat with a round to oval shape and they appear opaque. Upon maturity, the dark head capsule of the developing larva is clearly visible within the egg. The larvae may feed extensively just below the surface of the fruit, indicated by sunken, round, brownish areas. Mature fruits are roughened, blackish and generally distorted. Larvae feed on immature green fruit causing premature ripening (bluing) of fruit. The larvae also silk berries together when moving between fruit, but the frass from feeding stays entirely within the fruit, and the webbing is not obvious.

Lifecycle:
Larvae pupate in the spring, lasting for several weeks. Adult emergence begins after the start of bloom and usually before early fruit set. Adult flight continues through early July. Eggs are laid on small, developing green fruit, beginning at about the time of blossom drop. The eggs hatch in about a week and the young larvae, white with black heads, bore into and feed in the developing fruit. Larvae leave the fruit and enter a dead cane or weed to overwinter. There is 1 generation per year.

Links:

Scouting:

  • Watch for damaged developing green fruit, beginning at about the time of blossom drop. The young larvae, white with black heads, bore into the fruit.
  • As larvae feed and mature, they become pink with brown heads. These larvae can also be a harvest contaminant.
  • The 3 practical phases for monitoring for cherry fruitworm in blueberries include:
    1. monitoring adult trap catch,
    2. scouting for eggs, and
    3. scouting for larval infestations.
  • The emergence of adult males and moth flight can be monitored using sticky traps baited with female sex pheromone lures. Monitoring the emergence of adults provides two important pieces of information for pest management. First, the number of male adults caught in traps provides a relative estimate of population level and distribution within the field. Second, because egg laying typically begins shortly after initial adult emergence, adult catch in traps serves as an indicator for when egg monitoring should begin.
  • The second phase of monitoring fruitworms, scouting for eggs, provides the most reliable biofix for egg hatch timing and distribution in the field. Scouting for eggs should begin after there is some early blueberry fruit set and adult flight has commenced. Start by scouting along perimeter rows of blueberries that have a history of fruit worm pressure or are adjacent to woods and/or abandoned blueberry fields. Eggs are difficult to see because of their flattened shape and opaque color. A 15-20X hand lens is helpful to see eggs and confirm identification.
  • The third phase of monitoring fruitworm in blueberry is scouting for larval infestations. This is important for determining the effectiveness of the management strategy that has been utilized. Premature coloring of the fruit can be used to detect fruitworm infestations.

 
Cultural Controls:

  • If possible, eliminate host species (cherries).

 

For information about chemical controls, check with our Pesticide Guide.

images


photo from Michigan State University


photo from Michigan State University


photo by A. Artonelli

 

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