Submitted to: Progressive Crop Consultant
Publication Type: Popular Publication
Publication Acceptance Date: 5/20/2016
Publication Date: 5/31/2016
Citation: Klosterman, S.J. 2016. Spinach downy mildew – Threat, prevention and control. Progressive Crop Consultant. 1:12-15.
Technical Abstract: Downy mildew disease is a widespread and destructive disease of spinach in California and elsewhere where spinach is grown, and is caused by Peronospora effusa, an obligate, plant pathogenic oomycete. As in the case with most other crops damaged by downy mildews, spinach downy mildew culminates in the field with yellow spots on the leaves (chlorosis) that renders the fresh leafy product unmarketable. There is currently a lack of plant resistance to all the pathogenic variants of P. effusa and therefore there is a continual threat posed by the disease, especially to organic spinach production, where fungicides are not available for control. Organic spinach production has steadily increased in the United States over the past two decades, and spinach downy mildew outbreaks represent a serious threat to the sustainable production of this crop. Short term studies on pathogen detection in field leaf samples and as airborne samples can be useful for disease forecasting and in decision making on whether to harvest a field early in the case of organically grown crops. For conventionally grown crops, these studies can be useful for judicious application of fungicides. Ongoing efforts are aimed at determining levels of inoculum load of the pathogen associated with local disease outbreaks and various weather parameters to further aid in disease forecasting.