How to Manage Pests

UC Pest Management Guidelines

Lettuce

Beet Western Yellows

Pathogen: Beet western yellows virus

(Reviewed 4/17, updated 4/17)

In this Guideline:


Symptoms AND SIGNS

On lettuce, symptoms of beet western yellows rarely develop until plants reach rosette stage. At this point in crop development, the older leaves begin to turn yellow. This yellowing continues until all the oldest, lower leaves are bright yellow, or (less frequently) almost white, with the main leaf veins remaining green. Yellowed leaves often have a thick, brittle texture. Yellowing can progress until the wrapper leaves adjacent to the head also turn yellow, and head color may be unacceptably light green. In most lettuce varieties, significant stunting or reduction in plant size does not occur. Overall symptoms of this yellows disease may resemble nutrient deficiencies, such as iron chlorosis. This distinctive yellowing of older leaves sets this disease apart from other lettuce virus diseases.

Comments on the Disease

The disease is caused by Beet western yellows virus, which has an extensive host range, including over 150 documented plant species (see list below). Isolates or strains of this virus vary in their ability to infect different plant species; thus, not all strains of Beet western yellows virus may be able to infect all plant species, greatly complicating the study of this disease.

Beet western yellows virus is vectored by several aphid vectors, especially the green peach aphid. The virus is transmitted in a persistent manner by the aphid, meaning that once the aphid has acquired the virus by feeding on infected plants, that aphid can essentially continue to transmit the virus for the rest of its life. Unlike Lettuce mosaic virus, Beet western yellows virus is not seedborne in lettuce.

Partial List of Potential Host Reservoirs for Beet western yellows virus.
Host Agronomic Plants
Common Name Scientific Name
beet, sugarbeet Beta vulgaris
bell pepper Capsicum annuum
black mustard Brassica nigra
broccoli Brassica oleracea ssp. botrytis
cabbage Brassica oleracea ssp. capitata
cauliflower Brassica oleracea ssp. botrytis
chickpea/garbanzo bean Cicer arietinum
endive Cichorium endivia
escarole Cichorium endivia
fava bean Vicia faba
lettuce Lactuca sativa
mustard/rape Brassica napus
pea Pisum sativum
phlox, annual Phlox drummondii
radish Raphanus sativus
spinach Spinacia oleracea
spinach, New Zealand Tetragonia expansa
subterranean clover Trifolium subterraneum
sunflower Helianthus annuus
tomato Lycopersicon esculentum
turnip Brassica rapa
zinnia Zinnia elegans
 
Host Weeds
Common Name Scientific Name
blite, strawberry Chenopodium capitatum
chickweed, common Stellaria media
groundsel, common Senecio vulgaris
lettuce, prickly Lactuca serriola
mallow, little (Cheeseweed) Malva parviflora
saltbush, Australian Atriplex semibaccata
shepherd's-purse Capsella bursa-pastoris
sowthistles (Prickly Or Spiny) Sonchus asper

Management

In California this virus only occasionally causes significant economic damage. General virus disease management steps, such as those for Lettuce mosaic virus, apply to Beet western yellows virus as well.

Cultural Control

Control aphids, although insecticide programs will not prevent transmission of this virus and disease occurrence.

  • Eliminate or reduce virus reservoirs (weeds, volunteer lettuce, and old lettuce fields) with herbicide applications and cultural practices.
  • Consider resistant or tolerant varieties (currently, only few lettuce cultivars are reported to be resistant or tolerant to this virus).
Organically Acceptable Methods

Use cultural controls in an organically certified crop.

Chemical Control

There are no chemical controls for plant viruses.

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Lettuce
UC ANR Publication 3450

Diseases

S. T. Koike, UC Cooperative Extension, Monterey County
T. Turini, UC Cooperative Extension, Fresno County

Acknowledgment for contributions to Diseases:
R. M. Davis, Plant Pathology, UC Davis

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