WSU Whatcom County Extension

Integrated Pest Management for Blueberries

Pre-Bloom

Decision Making Matrices

 

Pest
Brief Description
Damage / Reason for Concern
Monitoring Approaches
Decision Points / Tolerances
Management Options
Follow Up
INSECTS

 

Aphids

Several species ranging from less than 1/16 inch to ¼ inch in length.  Color can range from light green or yellow to dark green or black.

Can cause deformation of developing leaves.
Can produce honeydew, which may cause sooty molds on foliage and fruit.
Acts as a vector for viruses, such as the Blueberry Scorch Virus.

Inspect 5 leaves at each plant.  Examine the undersides of leaves and inside the curled leaves of terminal shoot growth.

Aphid counts in low numbers will not cause economic damage; beneficial insects will keep population in check. Pre-Bloom treatment recommended in areas with scorch present.

Aphid populations respond to high nitrogen content in plant tissues.  Avoid over fertilization and excessive nitrogen levels.

Chemical

Revisit areas with aphid populations to determine whether the numbers are increasing or are being held in check by beneficial insects.

Wintermoth and Bruce Spanworm

Larvae are pale green with three white stripes developing on each side.
Head capsules of wintermoth are pale green.
Bruce spanworm have dark head capsules which can lighten to pale green.

Larvae feed on flower buds, flowers, and foliage.
Can contaminate harvested fruit.

Inspect 5 shoot tips per plant.
Look for silk, frass, discolored buds, and chewed entrance holes in buds.

Consider treatment if 5-10% of bushes have infested buds.
Insecticide treatment should be scheduled to target the hatching larvae.

Bacillus thuringiensis

Chemical

Continue scouting for larvae

DISEASES

 

Mummyberry

Mummified berries and mushroom-like spore cups may be seen on the soil surface under the plants. Floral and vegetative shoots are wilted and necrotic with a blackening in the center of the leaf.

Spores from ground will infect leaves and flowers.  This will cause infection on developing fruit resulting in non-saleable product.

Look for fallen berries, open, and inspect for developing spore cup. Search soil for mushroom-like spore cups.  Record level of incidence (low, medium, high).  Inspect 5 developing shoot tips per plant for infection.  Record % of tips with infection.

Detection is threshold for treatment.

Disrupt soil surface by raking  or cultivating around plants to destroy spore cups. 

Cover mummies with soil or mulch at least 2 inches deep.

Scout for leaf and flower infection during the next stage.

Godronia Canker

Cankers are seen as small reddish brown blemishes in early spring

If cankers get too large, they can girdle the stem.

Inspect several stems per plant for incidence of lesions. 

No tolerance established

Prune out infected wood.
Choose resistant varieties.

Educate farm workers on identification of cankers.

Botrytis

Infected tissue may appear blighted or be covered in a gray fuzzy mold.

Can cause leaf and stem death.  Can cause fruit rot after harvest.

Examine 5 branch tips at each plant.  Look for branch tips that are gray and brittle or dried up. Record # of plants with symptoms.

Consider traetment when infected twigs are found.

Remove infected plant material.
Avoid excessive use of nitrogen fertilizer in the spring.
Chemical treatment during bloom and fruit ripening.

Continue scouting for infection as new leaves and blossoms emerge. 

Bacterial Blight

Previous season’s canes are affected.  New tissue will appear black and older foliage will turn orange.  Foliage and flowers wilt.

Reduction in plant growth. 
Infection on blossoms to reduce yield.

Look for blighted tips on 20 bushes per site.  Symptoms are similar to Scorch Virus and Botrytis mold.  Test samples if unsure.

Threshold depends on market, weather, and variety grown. In mature planting, consider treatment when more than 10% of plants are infected.

Prune out diseased wood as soon as possible.

Continue monitoring for symptoms.  Tag plants showing symptoms to make sure Scorch or Botrytis are not present.

Shock Virus

Flowers and new leaves are unexpectedly dying.  Could be on one branch or whole plant.

Will cause a decrease in yield, often for only one year.  Symptoms are similar to that of Scorch virus which is much more problematic.

Visit 20 bushes at each site.  Record the number of plants exhibiting symptoms at each site.  Tag these plants and send samples to OSU to be tested.

Tolerances have not been established.  Testing plants is crucial to determine Scorch Virus is not present.

Plants will recover after one year of reduced yield.  No management options are available.

Continue monitoring plants throughout field and testing to eliminate the possibility of Scorch Virus.

VERTEBRATE PESTS

 

Voles

Small rodents tunnel through soil causing air pockets in the root zone.  They will also feed on roots

Can eat roots and girdle crowns.

Set up a monitoring station using PVC pipe and apple wedge.  Check for feeding damage on the apple wedge.

20-40% of monitoring stations are positive for feeding damage

Habitat reduction.
Rodenticide baits at bait stations.

Monitor again 2-3 weeks following treatment to evaluate efficacy.

 

Secondary content using h2 tag. Column 2

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

Heading using the h3tag

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

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