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Net Gains: Balancing CM control with Secondary Pests

Problem

Drape nets do a great job excluding codling moth – but they can also exclude natural enemies, leading to aphid outbreaks.

Project Goal

Use timing and degree of net deployment, plus releases of insectary natural enemies to solve the aphid problem, but still control CM.

Treatments

  1. Net fully closed at PF through harvest
  2. Net fully closed before CM gen. 2
  3. Net partly closed at PF
  4. Net full closed + predator releases (x3)
  5. Check – no net
  6. Check – no net + predator releases (x3)

Points to consider:

  • Nets installed/closed ca. 2 weeks late
  • Block had high CM pressure going into the test (high carryover)
  • Block had NO SPRAYS in the 2025 season
  • Next year we anticipate lower pressure in the netted plots (less carryover)

Results

Bar chart with treatments on the x-axis and wooly apple aphid colonies per 2 min count on the y-axis. Treatment 4, Net PF Full Predators, had the most woolly apple aphid colonies.
Figure 1. Wooly Apple Aphid

 

Bar chart with treatments on the x-axis and percent codling moth damage (stings and entries) on the y-axis. Treatment 2 Net G2 Full, 5 No Net No Preds, and 6 No Net Preds had the most insect damage.
Figure 2. Codling Moth Damage

 

  • Rosy apple aphid appeared early, and attracted large numbers of lady beetles. RAA were unaffected by nets.

Lady beetle larvae on an immature apple fruit,

  • Woolly apple aphid began building in late May, and were higher in one of the fully netted plots (trt. 4)

Image of woolly apple aphid white fuzzy wax secretions on a branch

  • Codling damage was lowest in the fully netted plots, even though they were closed about 2 weeks late

Image of apples with codling moth damage

Thanks to funders

Warmest thanks to the Washington Tree Fruit Research Commission for grant funding and DrapeNet for donation of nets, bullhorns and extenders.

Contact

Elizabeth H. Beers, Rebecca Schmidt-Jeffris, Adrian Marshall
WSU-TFREC/USDA-ARS Wapato
ebeers@wsu.edu

Image Gallery

 

Tree row with a net over the trees
Image 1. Net fully closed at PF (see disclaimer) through harvest

 

Image of tree row with net hung over trees, but not yet installed around the tree.
Image 2. Net fully closed before CM gen. 2

 

Tree row with a net over the trees
Image 3. Net partly closed at PF
Scientist inside of tree row netting releasing predators from a vial.
Image 4. Net fully closed + predator releases (x3)

 

Tree row with no net
Image 5. No net

 

Three images: first, of a tree row with no netting, second of a ladybird beetle on a leaf, third of a vial full of predatory insects.
Image 6. No net + predators

Pests and Natural Enemies: Sampled every other week
Codling moth fruit damage: 1x per generation

 

Fuzzy while colony on a branch
Image 7. Woolly Apple Aphid Colonies

 

New growth on a shoot with warped leaves
Image 8. Rosy Apple Aphid Colonies

 

Image of carboard rolled into a tube and tied to a tree - this is a common earwig trap.
Image 9. Earwigs

 

Image of a yellow sticky trap hanging in a tree.
Image 10. Lacewings, A. mali, etc.

 

Image of an orange tent trap for codling moth adults
Image 11. Codling Moth Adult Trap

 

Image of apples with codling moth damage
Image 12. Codling Moth Fruit Damage

 

Washington State University