WSU Whatcom County Extension

Integrated Pest Management for Blueberries

Pre-Harvest

Decision Making Matrices

 

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

 

Aphids

Winged and wingless aphids will be seen at this time.  Populations may be increasing quickly at this time of year.

Deformation of leaves; reduction of photosynthetic area.
May cause honeydew formation and sooty mold on fruit.
May transmit viruses; Scorch virus is especially problematic.

Check 5 leaves at each plant for adults and nymphs.  Record # of leaves with over 5 aphids per leaf.

Consider  treatment if:
When not in a scorch area: if 50% of leaves sampled have more than 5 aphids per leaf
When in a scorch area: if 10% of leaves sampled have more than 5 aphids per leaf.

Reduce excessive nitrogen use.  Aphids (and other piercing/ sucking insects) are attracted to high nitrogen tissues.

Chemical control.

Continue scouting for winged and wingless populations.

If chemical control was applied, scout 5 days following treatment to determine treatment efficacy.

Wintermoth and Spanworm

Maturing larvae feed on emerging foliage and developing fruit.

Larvae can defoliate new growth and flower buds causing a reduction in yield.

Inspect 5 fruit clusters per plant.  Look for webbing and frass in the fruit cluster

Consider treatment if 5-10% of plants have infested buds.

Chemical.
Be cautious of applying pesticides that may disrupt pollinators.

Treated fields should be scouted soon after treatment to determine efficacy.

Gall Midge

Eggs are laid in May and June in the new terminal growth.  Hatching larvae then feed in the terminals.

Can cause shoot tips to deform and curl and may result in excessive branching.

Inspect 5 shoot tips per plant at each site.
Look for blackened tips of developing shoots.  If seen, open up tips and use hand lens to identify maggots.

New Plantings: When more than 4 tips per plant with distortion. Pest is not an economic issue on established plantings.

No pesticides are labeled for Gall midge.

Main peaks of infestation are before and after harvest, when shoot tips are actively growing.  Scout during this stage and again post-harvest.

Leafrollers (OBLR)

Leaves may be rolled, chewed and tied together with silk and may be attached to fruit clusters.

Larvae can feed directly on fruit to reduce yield.  They can also act as a contaminant pest.  In general, they cause little damage on established plantings.

Inspect 5 leaves per plant.
Pull apart rolled leaves to confirm the presence of caterpillars.  Record number of larvae or damaged leaves found.

None established

Microbial insecticide B.t. with spreader sticker on cloudy day.

Chemical. 

Continue scouting for larvae at each site.

Root Weevils

Rough strawberry weevil adults emerge in June and July to lay eggs in summer.  Other species of root weevils may be present as adults, eggs, or larvae in the soil. 

Adult weevils can cause notching damage to leaves and new stems.
Larvae feed on and damage roots.

Examine 20 plants per site for adult feeding damage seen as notching on leaves and stems sometimes followed by flagging of stem sections.

Consider treatment if plants show signs of low vigor and weevils (adults or larvae) have been found. Thresholds depend on age of plant and variety grown. Young plants have a threshold of 1-3 larvae per plant.

Chemical.

Manage weeds in the infested area to eliminate alternate food sources for adults and larvae.

Continue scouting for adult and larval stages of weevils.

Spotted Wing Drosophila
(SWD)

Adults are small flies (less than 1/8 inch) with red eyes and a pale brown thorax and abdomen with black stripes on the abdomen. Adult males have a black spot towards the tip of each wing. Adult females have a large, saw-like ovipositor for inserting eggs into fruit.

This fly damages ripe and ripening fruit. Females lay 1-3 eggs per fruit by inserting their ovipositor into the fruit causing small scars, 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.

As soon as fruit begins to ripen place traps in fields using a 16oz plastic cup containing about ½” apple cider vinegar. Monitor traps twice per week and record number of adults found.

Also, monitor for small puncture (oviposition scar) wounds on fruit and soft fruit.

No threshold or tolerance level available.

In most cases detection is the advised threshold.

This is a new pest to the Pacific Northwest; therefore, thresholds and management are not well established.

Continue to monitor traps and check fruit for small scars and presence of larvae.

DISEASES

 

Mummyberry

Fruit will start to show symptoms; infected fruit will show white growth in the interior of the fruit and may fall to the ground prematurely.

Loss of yield due to infected fruit.

Inspect 5 fruit clusters at each plant.  Look for “early ripening of fruit” where infected fruit are turning a reddish color.  Cut open several fruit per cluster to look for whitish growth.

Treatment is not effective at this stage.  Monitoring is done to determine the disease pressure for the following year.

None at this stage

Watch for fallen berries during harvest.

Godronia Canker

Cankers are evident as reddish brown lesions on the stem.

Stem girdling when cankers get large.

Inspect 20 plants per site for infections on stems at wounded areas and leaf scars.

No tolerance established

Prune out infected wood.
Choose resistant varieties.

Educate farm workers on identification of cankers and pruning out methods.

Bacterial Blight

Only previous season’s growth is affected.  Disease enters through wounds in stem.

Stem girdling when cankers get large.  Buds in infected area will die.

Inspect plants for blighted tips and cankered twigs. 

No tolerance established

Prune out infected wood immediately to avoid spread.

Continue monitoring.
Educate farm workers on identification.

Botrytis

Gray fuzzy mold may be seen on developing berries at this time.

Fruit may become infected with gray fuzzy mold resulting in a reduced yield.

Inspect 5 fruit clusters per plant, especially during wet weather.  Look for gray fuzzy mold.

No established tolerance

Keep an open canopy to allow for good air circulation.
Time overhead irrigation so that foliage is not wet for prolonged periods.

Chemical

Continue scouting for botrytis infection of flowers and fruit.  Scout for infected fruit during harvest.

Shock Virus

Infected plants may start to show new growth at this time.

Decrease in yield for at least one season.  Plants usually recover after one season with symptoms.

Symptoms for Shock Virus are very similar to that of Scorch Virus.  Plants with Scorch Virus will not recover.  Proper identification is crucial.

Monitor plants tagged earlier as identified with symptoms.  These plants should be recovering at this time.  If they are not, make sure to have the tissue tested for other virus or disease problems.

No established tolerance; plants usually fully recover.

Plants should be recovering at this stage

Educate farm workers on identification of symptoms and how to mark plants for identification.  Identification should be done throughout the field.

Scorch Virus

Plants infected with Scorch Virus will not be recovering at this time as are those with Shock Virus.

Plant and field death.
This virus can be spread quickly through a field and between fields.  Vectors include aphids and people and tools moving between plants and fields.

Scouting for infected plants should be done through the entire field.  Plants suspected for Scorch (or Shock) Virus should be tested immediately.

Zero tolerance. 

No treatment available for this disease.
Plants must be removed from the field as soon as identified.

Continue monitoring and testing for virus in field.

Anthracnose

Fruit will begin to show symptoms of caving in on one side as they mature. Orange spore masses may also be seen.

Infected ripe fruit can cause a great reduction in yield.

Later in maturity, inspect 5 fruit clusters per plant.  Look for sunken shriveled berries sometimes with orange spores.  Rate the infection level (low, medium, high)

Consider treatment if levels of infection are medium to high, especially if weather is warm and wet. Threshold varies according to end product usage and processor.

Apply overhead irrigation so that plants do not stay wet for prolonged periods.

Prune plants to ensure good air circulation.

Chemical

Continue scouting up to and into harvest period.

Alternaria Fruit-Rot

Ripening fruit may show symptoms of caving in on one side with dark gray-green spore growth.

Infected ripe fruit is often not saleable.  Infection can greatly reduce yield.

Inspect 5 fruit clusters per plant.  Look for caving-in on one side as well as a dullish gray spore mass.  Rate the infection level (low, medium, high).

Consider treatment if levels of infection are medium to high. Threshold depends on end product usage and processor.

Avoid overripening by harvesting in a timely fashion.  Cool fruit immediately after harvest, and avoid wounding fruit during harvest.

Continue scouting up to and into harvest period.

VERTEBRATE PESTS

 

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.

Scout for birds in the early morning or just before dusk. Identify type of birds present, number present, and change in population size.

Consider treatment if problematic birds are present. Cater management plan to type and number of birds present.

Several types of management options are available. A management plan should be developed that is appropriate to farm site and surrounding properties.

Continue to scout for birds in the field and adapt management plan accordingly.

 

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