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Lettuce

Pests and their Damage—Heading to Harvest (Central Coast)

On this page
  • Botrytis crown rot
  • Corky root
  • Tip burn
  • Downy mildew
  • Lettuce dieback
  • Powdery mildew
  • Lettuce chlorosis
  • Tomato spotted wilt
  • Varnish spot
  • Leafminer
  • Green peach aphids
  • Lettuce aphid
  • Loopers
  • Thrips

See also, pests of other regions: Central Valley and Desert. Names link to more information on identification and management.

Click on photos to enlarge

Crown damaged by Botrytis rot
Botrytis rot damage
Identification tip: Damaged heads show gray spores on wilted, outermost leaves.

Corky root
Corky root damage
Identification tip: Roots show reduced feeder roots and a rough, pitted taproot.

Tip burn damage
Tip burn (warm weather)
Identification tip: Leaf tips turn brown.

Downy mildew
Downy mildew damage
Identification tip: Light green to yellow angular spots develop on the upper surface of the leaf.
Downy mildew
Downy mildew damage
Identification tip: Underneath the leaf, immediately below these angular spots, white fluffy fungal masses grow. With time lesions turn brown and dry up.
Powdery mildew
Powdery mildew
Identification tip: Appears as a white, powdery growth on both upper and lower sides of lettuce leaves.

Powdery mildew
Powdery mildew
Identification tip: Severe powdery mildew infection.

Lettuce dieback
Lettuce dieback
Identification tip: Outermost leaves are extensively yellowed. The younger, inner leaves often remain dark green in color, but can be rough and leathery in texture.

Lettuce chlorosis
Lettuce chlorosis
Identification tip: Symptoms of lettuce chlorosis and lettuce infectious yellows are virtually identical. Leaves exhibit severe yellowing, rolling, brittleness, and vein-clearing.

Tomato spotted wilt virus
Tomato spotted wilt
Identification tip: Iceberg lettuce develops necrotic lesions on leaves.
Varnish spot damage
Varnish spot (Pseudomonas cichorii) damaged head
Identification tip: Leaves exhibit dark brown spots that are firm and shiny.
Leafminer damage
Leafminers (Liriomyza spp.) damage
Identification tip: A larva mines between upper and lower leaf surfaces, creating winding tunnels that widen as the larva grows.

Potato aphid damage
Green peach aphids
Identification tip: Green peach aphids are dark green to yellow and have no waxy covering.

Looper damage to lettuce
Lettuce aphid
Identification tip: The adult has black markings on leg joints and antennae. They may have dark bands across their abdomen.
Looper damage to lettuce
Looper damage
Identification tip: Larvae feed primarily on the undersides of lower leaves, skeletonizing them and contaminating them with frass.
Western flower thrips damage
Western flower thrips damage
Identification tip: Leaves have feeding punctures and small, black, fecal deposits.
 

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