Dorman E A, Webster B J, Hausbeck M K
former Graduate Assistant.
Research Assistant.
Plant Dis. 2009 Apr;93(4):402-407. doi: 10.1094/PDIS-93-4-0402.
Alternaria dauci and Cercospora carotae cause foliar blight on carrot, causing yield reductions in severely blighted fields. Currently, fungicides are used on either a 7-day schedule or according to the TOM-CAST disease forecasting system. Organic production prohibits applications of most fungicides for blight control but does allow select copper-based products. The objective of this study was to use the TOM-CAST weather forecasting system to (i) assess the efficacy of copper hydroxide treatments for organic operations and (ii) evaluate the efficacy of reduced-risk products in an alternating spray program. Chlorothalonil, azoxystrobin, and copper hydroxide were applied alone or in alternating programs in 2001 and 2002. Reapplications were made on a 7-day schedule or according to TOM-CAST using disease severity value (DSV) thresholds of 10, 15, and 20. Area under the disease progress curve (AUDPC) data revealed that all application intervals significantly limited disease incidence on the foliage and petioles, resulting in healthier petioles at harvest compared with the untreated. The 7-day and TOM-CAST 10 DSV programs had comparable rating values for all parameters assessed and were more effective than the TOM-CAST 15 and 20 DSV programs in limiting petiole disease and maintaining overall petiole health. Copper hydroxide treatments resulted in higher AUDPC values and significantly different petiole health ratings compared with other treatments, yet P values indicated significant disease control compared with the untreated. The TOM-CAST 15 DSV program reduced sprays up to 40% compared with a 7-day interval and produced mean savings of $127/ha in 2001 and $137/ha in 2002.
胡萝卜链格孢和胡萝卜尾孢菌会引发胡萝卜叶枯病，在病害严重的田块会导致产量下降。目前，杀菌剂按照7天的施药间隔使用，或者根据TOM-CAST病害预测系统进行施药。有机生产禁止使用大多数用于防治叶枯病的杀菌剂，但允许使用特定的铜基产品。本研究的目的是利用TOM-CAST天气预报系统：（i）评估氢氧化铜处理对有机生产的效果；（ii）在交替喷雾方案中评估低风险产品的效果。在2001年和2002年，单独或按照交替方案施用了百菌清、嘧菌酯和氢氧化铜。按照7天的施药间隔重新施药，或者根据TOM-CAST系统，使用病害严重度值（DSV）阈值10、15和20进行重新施药。病害进展曲线下面积（AUDPC）数据显示，所有施药间隔都显著限制了叶片和叶柄上的病害发生率，与未处理的相比，收获时叶柄更健康。7天施药间隔和TOM-CAST 10 DSV方案在所有评估参数上具有相当的评级值，并且在限制叶柄病害和维持整体叶柄健康方面比TOM-CAST 15和20 DSV方案更有效。与其他处理相比，氢氧化铜处理导致更高的AUDPC值和显著不同的叶柄健康评级，但P值表明与未处理相比病害得到了显著控制。与7天的施药间隔相比，TOM-CAST 15 DSV方案减少了高达40%的喷雾次数，在2001年平均每公顷节省成本127美元，在2002年平均每公顷节省成本137美元。
