WSU Whatcom County Extension

Integrated Pest Management for Blueberries

Post Harvest

Biology and Monitoring

 

 
Insects
Diseases
Key Pests

 • Aphids
 • Root Weevils
 • Tent Caterpillars

 • Mummyberry
 • Bacterial Blight
 • Botrytis
 • Shock Virus
 • Scorch Virus

 

Biology

Aphids

Natural predators should have aphids under control at this stage. Winged aphids may be present at this time. If the scorch virus is a problem in your area, you may wish to control aphids during the dormant period.

 

Root Weevils

Root weevils overwinter either as larvae or adults. The obscure root weevil adults are more numerous between September and October. They are ¼ inch long with a wavy brown line across the back towards the rear. This species tends to spend the day hiding in the foliage instead of dropping to the soil.

 

Tent Caterpillars and Fall Webworms

Tents of the Fall webworm may be present until the middle of September. After maturing, the larvae will drop to the leaf litter to pupate and overwinter in the soil. Tent caterpillars will overwinter as egg masses on stems.

 

Mummyberry

Mummyberries produced during the current season will have dropped to the ground by this time. These will become the inoculant for the next season; cultural treatment at this time may reduce incidence of the disease in following years.

 

Godronia Canker

Red flags of dying leaves may be seen in infected plants. These leaves die earlier than those of healthy tissue. It is important to get rid of this tissue to reduce the amount of inoculant for the next year.

 

Bacterial Blight

Reddish black to brown cankers may still be seen. It is important to practice good pruning techniques to remove this tissue and to open the canopy for good air circulation.

 

Botrytis

Infected stem tips may appear gray or tan and dried out. Good pruning can help reduce infection in the next year.

 

Voles

Voles resemble house mice; they are 4-5 inches long, and gray or gray-brown in color. They create tunnels in the soil and can feed on fine roots or girdle stems. This tunneling also creates air pockets in the root zone. Vole populations are regulated by food availability and climatic conditions.

 

Monitoring

General Guidelines

Follow general guidelines in the "introduction" section.

Aphids

• Inspect 5 leaves per plant for incidence of aphids, especially winged aphids.

• Record the number of leaves with over 6 aphids found at each site.

• Consider treatment if the scorch virus is in your area and the population of winged adult aphids is not decreasing.

 

Root Weevils

• Check for adult Obscure Root Weevil leaf feeding by inspecting leaves for notching damage. Adults can also be found by placing a white cloth on the ground under the plant and shaking the plant onto the cloth. Obscure weevils should fall out of the foliage.

• Inspect the soil for larval root weevils. Dig around the root zone of several plants to look for c-shaped grubs.

• If root weevil damage has been detrimental or levels of root weevils are high, consider applying a nematode application in early Autumn when soil temperatures are still warm enough and larvae are young and susceptible. Preferably, time the treatment just before or during a rain event.

 

Tent Caterpillars and Fall Webworms

• Inspect branches for overwintering egg cases that appear as brown or gray hardened foam-like substance. They can be half inch long bands on twigs, or flattened shapes on tree trunks.

Management:
• Hand-pick or prune out the branches and twigs with egg masses during the post harvest and dormant season.

• Dormant oils may be applied in January and February to kill the eggs.

 

Mummyberry

• Scout for mummyberries fallen to the ground. If there has been a problem with this disease, consider cultural treatment.

Management:
After harvest and before leaf drop, cultivate shallowly to bury mummies. Berries that are buried 1 inch have been found to not cause infection in the following year.

 

Godronia Canker

• Look for the ‘red flags’ of dying leaves.

Management:
• Prune out infected wood

• Educate pruning crew on how to identify infection and prune out infected wood.

 

Bacterial Blight

• Look for reddish-brown to black cankers while pruning

Management:
• Prune out infected wood

• Educate pruning crew on how to identify infection and prune out infected wood.

 

Botrytis

• Look for tan or gray stem tips; black sclerotia may also be seen.

Management:
• Prune out infected wood

• Keep canopy open to encourage good air circulation

• Educate pruning crew on how to identify infection and prune out infected wood.

 

Voles

• Fall monitoring is done to determine populations before winter when crop damage can occur.

• Monitoring stations can be constructed using a protected shelter to cover a runway or tunnel entrance. Shelters can be constructed using roofing shingles or PVC piping. Place an apple wedge as bait underneath the shelter. Check the apple bait every 24 hours for 2-3 days. Inspect the apple wedge for feeding damage. Four to eight bait stations per acre can provide an accurate assessment of vole populations.

• Monitor again 2-3 weeks following treatment to determine efficacy.

Management:
• Treatment threshold ranges from 20-40% positive from monitoring station.

• Habitats can be changed to reduce vole problems

• Remove debris piles

• Regularly mow field margins and keep large weeds under control

• Pelletized baits can be broadcast, but they degrade quickly.

• Bait stations can be made by making a T out of 2-3 inch PVC pipe filled with bait. (see profile page for more information)

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