Evaluation location: New York, United States
2024 Germplasm Evaluation of diverse hemp germplasm in an outdoor field in Geneva NY for Septoria leaf spot and powdery mildew, see USDA-ARS PN 8060-21000-034-031-A [https://www.ars.usda.gov/research/project/?accnNo=445656]. One hundred and five accessions were selected for evaluation during the summer of 2024. Seeds were sown indoors on May 15th, 2024, and seedlings were transplanted to the McCarthy 001 field on May 28th of 2024, using a randomized complete block design with three blocks and a target number of five plants per block. Transplants were spaced three feet apart on raised beds, and landscape fabric was laid between rows to reduce weed pressure. Drip irrigation was used for watering when needed. An initial inoculation with a spore suspension of Golovinomyces ambrosiae spores was conducted on June 27th, 2024. The first powdery mildew colonies were observed on leaves in mid-July, and differential levels of disease were quantifiable by the end of that month. Disease was assessed visually as percent disease on a scale from 0-100% of a whole plant leaf area. Individual plants were rated on August 1st, 7th, 12th, 20th and 28th. Flowering time and sex were evaluated on a weekly basis. For plants that hadn't flowered by October 5th, one or two weeks in the future were estimated based on visual floral development. Although many plants of Chinese origin are among the least susceptible ones as of the last rating, many showed signs of disease as they approached flowering”