WSU Whatcom County Extension

Integrated Pest Management for Blueberries

Harvest

Biology and Monitoring

 

 
Insects
Diseases
Key Pests
 • Aphids
 • Fruit Contaminants
 • Spotted Wing Drosophila
 • Mummyberry
 • Godronia Canker
 • Botrytis
 • Shock Virus
 • Scorch Virus
 • Anthracnose
Occasional Pests
 • Gall Midge
 • Scale
 • Symphylans
 • Cherry Fruitworm
 • Root Weevils
 • Phomopsis Canker

 

Biology

Aphids

Aphids continue to produce offspring until late fall, but the rate of population increase is lower at this time.

 

Fruit Contaminants

These are primarily egg sacs of spiders or pupae of lacewing and syrphid flies that are contained in the blossom end of the berry. They usually appear as a white furry mat in the calyx end of the fruit. Spiders, lacewings, and syrphid flies are considered beneficial, so controlling them is often not recommended; this may result in outbreaks of pests such as thrips, mites, aphids, and caterpillars. The best way to manage this problem is to remove contaminated fruit on the grading lines after harvest.

 

Spotted Wing Drosophila

At higher temperatures (above 86F), fly activity, egg laying and longevity may decrease. This may result in fewer generations per year, but damage may still occur. Infestation of fruit reveals small scar, indented soft spots, and bruises on the fruit surface. Eggs hatch and the larvae develop and feed inside the fruit, causing the flesh to collapse around the feeding site within as few as two days. Fungal and bacterial infections and secondary pests may contribute to further fruit deterioration. Larvae are small (less than 1/8 inch), cylindrical and white to cream colored. More than one larva may be found feeding within a single fruit.

 

Mummyberry

Infected berries will show up in the clusters and drop to the ground to overwinter. Mummyberries first appear pink and puckered looking. The inside tissue is brown and corky. As it ages, it turns white and withered and dried.

 

Godronia Canker

Cankers are still growing in size through the season. The cankers will start to appear more like a bull’s eye, with gray centers and a reddish-brown outside.

 

Blueberry Shock Virus

Infected plants appear normal in late summer except for the lack of fruit. Plants may fully recover after the first year or may show symptoms for up to three years. Symptomless plants still carry the virus.

 

Blueberry Scorch Virus

Plants with scorch virus will not show recovery at this time. Fruit and shoot production are drastically reduced on infected plants. Testing and removal of plants is necessary to control the spread of this virus.

 

Botrytis

This fungus becomes more active on fruit as they ripen. Wet and warm weather conditions can increase the spread of the disease.

 

Anthracnose Ripe-Rot

Ripening infected berries will start showing symptoms of the blossom end softening and salmon colored spore masses may be seen. Warm and rainy conditions will increase the spread of this disease.

 

Alternaria Fruit-Rot

Alternaria infections occur from late bloom to fruit maturity but symptoms will not show until fruit is ripening or even until fruit is in storage. Infected berries will cave in at the sides and may have greenish-gray spores. If infection spreads through harvested fruit in storage, yield losses can be great.

 

Birds

Several types of birds may be present and have the potential to cause damage in a field. Starlings, robins, house finches, and red-winged blackbirds are common. Damage to fruit can be caused in several ways; fruit may be knocked off of bushes during foraging, eaten wholly by the bird, or punctured or pecked at by a bird.

 

Monitoring

General Guidelines

See general guidelines in the "introduction" section.

 

Aphids

• At each site, inspect 5 leaves per plant.

• Look for winged and wingless aphids as well as aphid mummies that have been parasitized by aphid parasitic wasps. Also, look for beneficial insects such as ladybug larvae, lacewing larvae, and syrphid larvae.

• The presence of honeydew and sooty mold on fruit and leaves indicates a high aphid population. Make a note if you find this condition.

 

Fruit Contaminants

• Inspect 5 fruit clusters per plant for contaminants at the blossom end.

• Record this number and train harvesting and processing crew to be aware of these contaminants.

 

Spotted Wing Drosophila

• Monitor traps twice per week and record number of adults found. Also monitor for small puncture (oviposition scar) wounds on fruit and soft fruit. Adults are attracted to ripe or ripening fruit.

• Record the number of adults found per trap and the percentage of contaminated fruit.

• Check soft fruit on the cane as well as on the harvester/processing belt for the presence of larvae.

 

Mummyberry

• At each plant, check 5 berry clusters for mummyberry symptoms.

• Examine the ground beneath the plants to see if any infected fruit has fallen to the ground.

Management:
• If on a small farm, clean up dropped fruit following harvest. The use of geese may also be used to clean up the dropped fruit as well as weeds.

 

Godronia Canker

• Inspect 20 plants per site

• Look for leaves turning color earlier than normal. These leaves will turn bright red/brown and remain attached – looking like red flags in the field.

 

Blueberry Shock Virus

• Visit marked plants at each site and throughout field to observe recovery from shock virus.

• Symptomatic plants should be sent to a diagnostic lab immediately to determine if scorch is present.

 

Blueberry Scorch Virus

• Plants with scorch symptoms should be sent for testing immediately.

• Symptoms include leaf dieback and blighted blossoms remaining on the plant.

 

Botrytis

• Inspect 5 fruit clusters per plant. Observe fruit for fuzzy gray mold during harvest.

• Fruit should be harvested frequently where gray mold is commonly seen, especially in conditions of wet and warm weather.

 

Anthracnose Ripe-Rot

• Inspect 5 fruit clusters per plant for signs of infection.

• Symptoms include softening at the blossom end and masses of salmon colored spores.

Management:
•To reduce the spread among harvested fruit, reduce the temperature of the fruit to 32°F as soon as possible.

 

Alternaria Fruit-Rot

• Inspect 5 fruit clusters per plant.

• Look for fruit with sides caving in and greenish-gray spores.

• Rate the level of infection (low, medium, high)

Management:
• Avoid over ripening by harvesting in a timely fashion.

• Cool fruit immediately after harvest.

 

Birds

• Scout for birds in the early morning or just before dusk. Identify type of bird present, number present, and change in population size.
• Continue monitoring through harvest

Management
• Several types of management options are available. A management plan should be developed that is appropriate to farm site and surrounding properties.
• Adapt management plan according to scouting levels

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WSU Whatcom County Extension • 1000 N. Forest St., Bellingham, WA 98225 • (360) 778-5800 • whatcom@wsu.edu