WSU Extension

Hortsense

Lettuce
 
Disease
Anthracnose 
Aster yellows 
Beet western yellows virus 
Bottom rot 
Damping-off 
Downy mildew 
Lettuce big vein virus 
Insect
Aphids 
Slugs 



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Caption: Aphid colony
Photo by: A.L. Antonelli
  
Lettuce : Aphids
(revision date: 3/10/2017)


Biology
Aphids are small, soft-bodied, pear-shaped insects. They may vary in color from yellow to green to dark. Aphids typically feed in colonies on the leaves, often preferring the newer growth. Infested leaves turn yellow and may wilt or show other signs of water stress. Feeding aphids often produce large amounts of honeydew, a sweet, sticky material which may attract ants or become covered with a dark growth of sooty mold. The ants may protect aphid colonies from predators.
Management Options


Non-Chemical Management
  • Encourage natural enemies including ladybird beetles, lacewings, syrphid (hover) fly larvae, and parasitic wasps. Avoid use of broad-spectrum insecticides which kill beneficial insects.
  • Hand-wipe to help control small, localized infestations.
  • Wash aphids from plants with a strong stream of water. This may be ineffective on the low, dense foliage of lettuce.
  • Control honeydew-feeding ants.
  • Provide proper nutrition. High levels of nitrogen in the foliage encourage aphid reproduction. Switch to a slow-release or low-nitrogen fertilizer when practical.
  • Wash lettuce before eating.
Select non-chemical management options as your first choice!

Chemical Management

Follow label directions. Apply when aphids first appear.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
    Active ingredient: azadirachtin  |  EPA reg no: 70051-6-42697
  • Safer Brand Insect Killing Soap with Seaweed Extract II [Organic]
    Active ingredient: potassium laurate  |  EPA reg no: 42697-59
  • Surround At Home Crop Protectant
    Active ingredient: kaolin clay  |  EPA reg no: 61842-18-56872
  • This list may not include all products registered for this use.
Images

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Caption: Aphid colony
Photo by: A.L. Antonelli
Caption: Aphid cast skins
Photo by: R.S. Byther
Caption: Aphids on kale
Photo by: C.A. Miles