Cause Albugo occidentalis, a fungus that is not uncommon on spinach but usually of minor importance. It also infects weedy species of Chenopodium. Warm days followed by cool, dew-forming nights favor disease.
Symptoms White pustules will develop on the lower, sometimes upper surface of infected leaves as well as on petioles, and the upper leaf surface will be yellowish.
Cultural control
- Bury infected host residue by deep-plowing.
- Do not plant spinach in consecutive years. Three-year rotations may be necessary.
- Control susceptible weeds.
Chemical control
- Actigard 50WG (Group P1) at 0.5 to 0.75 oz/A every 7- to 10-days controls disease by inducing host-resistance pathways. Do not apply within 7 days of harvest. 12-hr reentry.
- Copper formulations (Group M1) offer limited control.
- Badge SC at 1 to 2.25 pints/A on 7- to 10-day intervals. Preharvest interval is 0 days. 24-hr reentry for greenhouse use; 48-hr reentry for all other applications.
- Bonide Liquid Copper is available for home gardens. H
- Cueva at 0.5 to 2 gal/100 gal water on 7- to 10-day intervals. May be applied on the day of harvest. Poor control as a stand-alone product. 4-hr reentry. O
- Previsto at 0.75 to 2 quarts/A on 7- to 10-day intervals. 48-hr reentry. O
- Presidio (Group 43) at 3 to 4 fl oz/A on 10-day intervals in combination with another fungicide that has a different mode of action. Preharvest interval is 2 days. 12-hr reentry.
- Ridomil Gold Copper (Group 4 + M1) at 2 lb/A as 1 or 2 applications on a 14-day interval. Preharvest interval is 3 days. 48-hr reentry.
- Strobilurin formulations (Group 11) are labeled for use. Do not apply more than one (1) foliar application of any Group 11 fungicide before alternating to a labeled fungicide with a different mode of action.
- Arius 250 at 6 to 15.5 fl oz/A on 10- to 14-day intervals starting prior to disease onset. Preharvest interval is 0 days. 4-hr reentry.
- A-Zox 25 SC at 6 to 15.5 fl oz/A on 7- to 14-day intervals starting prior to disease onset. Preharvest interval is 0 days. 4-hr reentry.
- Azoxystar at 6 to 15.5 fl oz/A on 7- to 14-day intervals starting prior to disease onset. Preharvest interval is 0 days. 4-hr reentry.
- Azoxyzone at 6 to 15.5 fl oz/A on 7- to 14-day intervals starting prior to disease onset. Preharvest interval is 0 days. 4-hr reentry.
- Azteroid FC 3.3 at 3.9 to 9.7 fl oz/A on 7- to 14-day intervals starting prior to disease onset. Preharvest interval is 0 days. 4-hr reentry.
- Cadera at 6 to 15.5 fl oz/A on 7- to 14-day intervals starting prior to disease onset. Preharvest interval is 0 days. 4-hr reentry.
- Reason 500 SC at 5.5 to 8.2 fl oz/A on no shorter than 5-day intervals. Preharvest interval is 2 days. 12-hr reentry.
- Tigris Azoxy 2 SC at 6 to 15.5 fl oz/A on 7- to 14-day intervals starting prior to disease onset. Preharvest interval is 0 days. 4-hr reentry.
- Trevo at 6 to 15.5 fl oz/A on 7- to 14-day intervals starting prior to disease onset. Preharvest interval is 0 days. 4-hr reentry.