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Western Flower Thrips

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Hosts:  apple, nectarine


Biology:
  Overwinter as adults in protected areas on the ground and emerge in spring and feed on and lay eggs within, flower parts.   Adults sometimes also feed on young fruit, but are not generally a pest on apples after bloom.  They may feed on older nectarine fruit, causing russeting.


Symptoms/Damage:

  • Nectarine:  scarring, russeting, deformation
  • Apple:  “pansy spot” most visible on light-skinned cultivars.


Monitoring:
  Shake flower clusters vigorously into a cup or jar.  Test 5 clusters on 5 trees per 10 acres.


Treatment Threshold:
  In light-skinned apple varieties, treat if there is more than 2 adults per cluster.  In nectarine, treat if there is more than 1 adult per cluster.


Degree Day Model:
  None


Management Considerations:
  Minute pirate bugs and lacewings are important predators late in the season to help reduce populations the following spring. 

Treat at petal fall for best control, after bees have been removed from the orchard.