HPIPM:Downy Mildew Spinach

Taxonomy

Domain	Eukarya
Kingdom	Chromista
Phylum	Oomycota
Class	Oomycetes
Order	Peronosporales
Family	Peronosporaceae
Genus	Peronospora

Scientific Name

Peronospora farinosa

Scientific Name Synonyms

Peronospora effusa

Common Name

downy mildew

Author: Howard F. Schwartz and David H. Gent

Identification and Life Cycle

Downy mildew of spinach is caused by the fungus-like organism Peronospora farinosa f. sp. spinaciae (syn.= P. effusa). Downy mildew is a very common and often destructive disease of spinach in the High Plains during cool, wet conditions. The pathogen is disseminated within and among fields by wind and splashing water droplets. At least four races of the downy mildew pathogen have been identified, but all races of the pathogen are not present in the High Plains spinach production regions. The pathogen survives between spinach crops in and on dead spinach plants, crop residues, volunteer spinach and some weeds, and in infested seed.

Plant Response and Damage

Downy mildew symptoms first appear as pale yellowish spots with a gray to purple downy growth on leaf undersurfaces. This downy growth is most apparent during wet weather. Infections may be scattered or numerous, but individual lesions often coalesce. Severely infected plants are stunted or die. Downy mildew can reduce both spinach yield and quality, and can be quite damaging to susceptible cultivars during cool, wet weather.

Biological Control

Biological control strategies have not been developed for downy mildew.

Cultural Control

Several resistant varieties have been developed and should be planted if suitable for your production and marketing needs. Varieties need to be selected carefully to match the prevalent pathogenic races in your specific production region. Practice a three-year or longer crop rotation to nonhosts such as small grains and corn. Reduce prolonged periods of leaf wetness by increasing row spacing, orientating rows parallel to the prevailing wind direction, and avoiding overhead irrigation. If possible, time irrigation to end before dusk to avoid extended periods of leaf wetness. Promptly and thoroughly incorporate crop residues and volunteer spinach to reduce pathogen survival and overwintering.

Chemical Control

Chemical controls are most effective when integrated with sound cultural control practices. Copper-based fungicides may leave unattractive residues on leaves and make them unmarketable.

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.