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Lettuce

Pests and their Damage—Heading to Harvest (Desert)

On this page
  • Big vein
  • Botrytis crown rot
  • Tip burn
  • Gray mold
  • Corky root
  • Downy mildew
  • Bottom rot
  • Powdery mildew
  • Varnish spot
  • Lettuce chlorosis
  • Western flower thrips
  • Leafminers
  • Potato aphids
  • Green peach aphids

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

Click on photos to enlarge

Big vein
Big vein damage
Identification tip: Veins in leaves become enlarged and clear; easily seen if leaf is examined with the light source behind it. Enlarged veins cause the rest of the leaf to be ruffled and malformed.

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

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

Tip burn damage
Gray mold (Botrytis cineria) damage
Identification tip: Infected foliage is covered with gray spores.

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

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.

Downy mildew
Bottom rot (Rhizoctonia diseases)
Identification tip: Brown sunken lesions form on midribs in contact with soil. Lesions may expand to rot lower leaves.

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.

Varnish spot damage
Varnish spot (Pseudomonas cichorii) damaged head
Identification tip: Leaves exhibit dark brown spots that are firm and shiny.
Lettuce chlorosis virus
Lettuce chlorosis
Identification tip: Symptoms of lettuce chlorosis and lettuce infectious yellows are virtually identical. Leaves exhibit severe yellowing, rolling, brittleness, and vein-clearing.
Western flower thrips damage
Western flower thrips damage
Identification tip: Leaves have feeding punctures and small, black, fecal deposits.
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
Potato aphids
Identification tip: Potato aphids can be green or pink.
Potato aphid damage
Green peach aphids
Identification tip: Green peach aphids are dark green to yellow and have no waxy covering.
 

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