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Lettuce
> Year-Round IPM Program > Heading
to Harvest > Pest
Damage (Desert)
Lettuce
Pests and their Damage—Heading to Harvest (Desert)
On this page
- Big vein
- Botrytis crown rot
- Tip burn
- Gray mold
- Corky root
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- Downy mildew
- Bottom rot
- Powdery mildew
- Varnish spot
- Lettuce chlorosis
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- Western flower thrips
- Leafminers
- Potato aphids
- Green peach aphids
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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 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.
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Botrytis rot damage
Identification tip: Damaged heads show gray spores on
wilted, outermost leaves.
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Tip burn (warm weather)
Identification tip: Leaf tips turn brown.
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Gray mold (Botrytis cineria) damage
Identification tip: Infected foliage is covered with gray spores.
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Corky root damage
Identification tip: Roots show reduced feeder roots
and a rough, pitted taproot. |
Downy mildew damage
Identification tip: Light green to yellow angular spots
develop on the upper surface of the leaf.
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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.
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Bottom rot (Rhizoctonia diseases)
Identification tip: Brown sunken lesions form on
midribs in contact with soil. Lesions may expand to rot
lower leaves.
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Powdery mildew
Identification tip: Appears as a white, powdery growth
on both upper and lower sides of lettuce leaves.
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Powdery mildew
Identification tip: Severe powdery mildew infection.
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Varnish spot (Pseudomonas
cichorii) damaged head
Identification tip: Leaves exhibit dark brown spots
that are firm and shiny. |
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
Identification tip: Leaves have feeding punctures
and small, black, fecal deposits.
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Leafminers (Liriomyza spp.)
damage
Identification tip: A larva mines between upper
and lower leaf surfaces, creating winding tunnels that
widen as the larva grows.
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Potato aphids
Identification tip: Potato aphids can be green or
pink. |
Green peach aphids
Identification tip: Green peach aphids are dark
green to yellow and have no waxy covering. |
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