Survey of Powdery Mildew and Gray Mold Disease Management in Virginia and North Carolina Cut Flower Farms

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Virginia Tech


Powdery mildew and gray mold diseases have potential to cause significant economic losses to cut flower growers. Information is needed on the effects of these diseases on growers’ returns and the effectiveness of practices to control the diseases. A survey was conducted to examine powdery mildew and gray mold disease management practices on cut flower farms in North Carolina and Virginia. Twenty cut flower farmers completed an online survey and eight of those respondents also participated in an interview. The survey gathered information about the farms, such as its acreage and number of years growing cut flowers, flower genera affected by the diseases, fungicide use and efficiency, and cultural control use and efficiency. The survey and subsequent interviews provided several major findings. First, the floral genera most affected by powdery mildew in North Carolina and Virginia were Zinnia, followed by Dahlia. The genera most affected by gray mold were Ranunculus, followed by Anemone and Dahlia. Second, crop loss due to each disease was mostly at the 0 to 10% level, with one farm losing 91 to 100% of Phlox crops to powdery mildew and another losing 81 to 90% of Tulipa crops to gray mold. Third, 40% of respondents have not used any fungicides for disease management; and for those who have, neem oil was the product they used most frequently. Fourth, all respondents considered sustainability very important when making disease management decisions; this was supported by their extensive use of cultural practices for disease control, in addition to their preference of nonchemical approaches and biorational products over synthetic pesticides. The commonly used cultural controls included, crop rotation, proper watering, disease resistant cultivars, sanitation, proper spacing, and weeding. Findings from this survey will help cut flowers growers in the Mid-Atlantic region to better manage these two important diseases.