An Evaluation of Eight Basil Cultivars for Downy Mildew Resistance in Virginia

Production of fresh herbs is a trendy market that continues to grow in popularity in the United States. Basil (Ocimum baasilicum) is such an herb that is experiencing growth in popularity, especially sweet basil. In Virginia, sweet basil production is increasing and can occur both within the field and greenhouses. However, basil production faces certain challenges, with the most serious one being disease losses caused by downy mildew. With few effective control measures available it is important to find management practices that can assist in controlling this disease, particularly in organic systems. Thus, studies were performed examining eight different sweet basil cultivars during the summer growing season of 2019. The study took place at Adam’s Apples and Herbs, located in Shenandoah County in the Shenandoah Valley of Virginia and at Virginia Tech’s Eastern Shore Agricultural Research and Extension (ESAREC) in Painter. At harvest, basil was weighed, by leaf and by stem, and then an average of the weight was calculated as was the height of each cultivar. Disease incidence and severity for each basil cultivar was recorded throughout the course of the study. Little disease occurred during the course of the study in the Shenandoah Valley. However, significant differences in basil cultivar growth and appearance were noted. At the ESAREC, downy mildew did develop and resistant cultivars proved to be effective at suppressing disease.