How to Manage Pests

UC Pest Management Guidelines

SYMPTOMS

Symptoms of lettuce chlorosis and lettuce infectious yellows are virtually identical. Leaves exhibit severe yellowing, rolling, brittleness, and vein-clearing. Plants infected early are stunted.

COMMENTS ON THE DISEASES

These diseases occur in lettuce grown in the southern deserts of California. Both viruses have wide host ranges with one significant difference: Lettuce infectious yellows virus infects cucurbits while Lettuce chlorosis virus does not. This is important in the epidemiology of these diseases because fall-planted cucurbits, which were a major crop in the past and an important reservoir of Lettuce infectious yellows virus, are now a minor crop. Both viruses are transmitted by whiteflies. However, Lettuce chlorosis virus is transmitted by Bemisia tabaci and B. argentifolii with about the same efficiency while Lettuce infectious yellows virus is transmitted very inefficiently by B. argentifolii. Because B. argentifolii is the dominant whitefly species in the desert growing areas and fall-planted cucurbits have become minor crops, lettuce infectious yellows disease is now a minor problem. Weed hosts are apparently the major source of lettuce chlorosis and barring any major change in cropping patterns in the desert, the incident of these viruses should remain low.

MANAGEMENT

A reduction of whitefly populations and removing weed sources may reduce these diseases; however, specific controls are not generally practiced.

PUBLICATION

UC IPM Pest Management Guidelines: Lettuce
UC ANR Publication 3450
Diseases
S. T. Koike, UC Cooperative Extension, Monterey Co.
R. M. Davis, Plant Pathology, UC Davis

Top of page