HPIPM:White Rust Spinach

Taxonomy

Domain	Eukarya
Kingdom	Chromista
Phylum	Oomycota
Class	Oomycetes
Subclass	Albuginomycetidae
Order	Albuginales
Family	Albuginaceae
Genus	Albugo

Scientific Name

Albugo occidentalis

Common Name

white rust

Author: Howard F. Schwartz and David H. Gent

Identification and Life Cycle

White rust is caused by the fungus-like organism Albugo occidentalis. This pathogen is more closely related to downy mildew-type pathogens than the true rust pathogens. The source of the white rust pathogen that initiates epidemics is not known, but the pathogen is known to survive in infested crop debris as dormant resting structures (oospores) and, in milder climates, as mycelia and sporangia. Oospores are thought to disseminated by splashing rain and irrigation water, and possibly by blowing soil. In warmer climates, sporangia produced on weeds can be deposited onto spinach by wind, whereupon they germinate and produce a mobile spore called a zoospore. Zoospores penetrate plants through natural openings, eventually germinate, and form mycelia in spinach tissues. Disease is favored by cool to moderate temperatures (50 to 68ºC) and abundant rainfall.

Diseased spinach plants produce windblown sporangia that serve as secondary inoculum, infecting other plants and beginning the disease cycle again. Oospores eventually form in diseased tissue and overwinter in infested crop debris and the soil.

Plant Response and Damage

White rust symptoms initially appear as white, blister-like pustules on the lower surface of leaves. Opposite these pustules on the upper surface of the leaf may be a yellowish spot. The disease can reduce spinach yield, quality, and marketability.

Biological Control

No biological control strategies have been developed for white rust of spinach.

Cultural Control

Practice a three-year or longer crop rotation to nonhosts with strict sanitation of weeds and volunteer spinach.

Chemical Control

Chemical control strategies are most effective when integrated with sound cultural practices.

Due to constantly changing labels, laws and regulations, the sponsors of this web site assume no liability for the suggested use of any chemicals noted in the management section. Contact your local pest management personnel for current information on labeled pesticides that can be used for the intended plant disease, insect pest or weed.