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.

Top of page

Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright © 2017 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.

Agriculture and Natural Resources, University of California

Accessibility   /PMG/C441/m441hppests.html revised: June 19, 2017. Contact webmaster.