Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI 48824.
Plant Dis. 2021 Jul;105(7):1880-1889. doi: 10.1094/PDIS-01-20-0023-RE. Epub 2021 Jul 13.
Hops have expanded as a niche crop in Michigan and other production areas in the eastern United States, but growers in these regions face annual downy mildew outbreaks incited by , exacerbated by frequent rainfall and high relative humidity. We evaluated the efficacy of foliar- and drench-applied fungicides against downy mildew and examined Michigan isolates for point mutations linked to carboxylic acid amide (CAA) resistance. Disease severity and density were assessed weekly in 2016 and 2017 in nontrellised research hop yards in Michigan. Area under the disease progress curve values for disease severity were significantly lower for plants treated with oxathiapiprolin, ametoctradin/dimethomorph, fluopicolide, cyazofamid, or mandipropamid (90.6 to 100% control) compared with those treated with fosetyl-Al (64.3 to 93.0% control) at both locations for both years. Drench treatments of fluopicolide and oxathiapiprolin/mefenoxam reduced disease density and severity at both locations but were only moderately effective (76.4 to 91.5% control). To assess CAA resistance, the cellulose synthase gene was aligned using reference downy mildew species and primers designed to amplify the 1105 and 1109 amino acids. Point mutations conferring CAA resistance were not detected at these loci for sporangia from 42 symptomatic shoots collected from 11 commercial hop yards. These efficacy results for hop downy mildew are needed to guide disease recommendations in this expanding Michigan industry. The absence of resistant genotypes indicates that Michigan growers can continue to utilize CAA-containing commercial fungicides as part of an overall downy mildew management program.
啤酒花已在美国东部的密歇根州和其他产区作为特色作物得到了扩展，但这些地区的种植者每年都面临由 引发的霜霉病爆发，频繁的降雨和高相对湿度加剧了这种情况。我们评估了叶面喷雾和灌根施用药剂防治霜霉病的效果，并检查了与羧酸酰胺（CAA）抗性相关的点突变的密歇根分离物。在 2016 年和 2017 年，我们在密歇根州的非蔓生研究啤酒花田每周评估一次疾病严重程度和密度。与使用乙膦铝（64.3 至 93.0%的防治效果）相比，使用唑噻菌胺、唑醚代森联、氟吡菌酰胺、氰霜唑或双炔酰菌胺处理的植物的病情严重程度的病害进展曲线下面积值显著更低（90.6 至 100%的防治效果），在这两个地点的两年中均如此。在这两个地点，氟吡菌酰胺和唑噻菌胺/肟菌酯的灌根处理均降低了病情密度和严重程度，但效果仅为中度（76.4 至 91.5%的防治效果）。为了评估 CAA 抗性，使用参考霜霉菌种和设计用于扩增 1105 和 1109 个氨基酸的引物对纤维素合酶基因进行了比对。在从 11 个商业啤酒花田的 42 个有症状的嫩枝上收集的孢子囊中，未在这些基因座检测到赋予 CAA 抗性的点突变。这些啤酒花霜霉病的功效结果可用于指导该州不断扩展的产业的疾病推荐。缺乏抗性基因型表明，密歇根州的种植者可以继续将含有 CAA 的商业杀菌剂作为综合霜霉病管理计划的一部分加以利用。
