Woodward J E, Brenneman T B, Mullinix B G
Extension Plant Pathologist, Texas AgriLife Extension Service, Lubbock, TX 79403-6603 and Associate Professor, Department of Plant and Soil Science, Texas Tech University, Lubbock 79409-2122.
Professor, Department of Plant Pathology.
Plant Dis. 2012 Dec;96(12):1785-1790. doi: 10.1094/PDIS-01-12-0042-RE.
Fungicides not reaching target organisms result in decreased disease control. In the southeastern United States, foliar-applied fungicides are routinely used to manage peanut (Arachis hypogaea) diseases. Irrigation is often applied to wash fungicides from treated foliage to obtain maximum control of diseases caused by soilborne pathogens. Administering irrigation before fungicide residues have dried may adversely impact foliar disease control. A microplot study was conducted in 2003, 2004, and 2005 to evaluate the redistribution of azoxystrobin, tebuconazole, and flutolanil plus chlorothalonil following different irrigation timings. Standard fungicide regimes were subjected to 1.3-cm of irrigation 0, 6, 12, 24, 48, or 96 h after application, and a nonirrigated control was included. Microplots not receiving irrigation were covered while irrigation treatments were administered. Irrigation timing was significant for the number of early leaf spot (Cercospora arachidicola) lesions per leaf. Leaf spot was more severe when irrigation was administered immediately following fungicide applications, and was significantly reduced with a 6- and 12-h delay prior to an irrigation event, whereas maximum control was obtained when irrigation was delayed for 24 h or later. To further quantify fungicide residue distribution, Sclerotium rolfsii was used to bioassay foliage and pods. Lesion development on leaflets, which was greater for earlier irrigation timings, did not differ for the 12-h and later timings and was generally similar to the nonirrigated controls. Pod colonization for all fungicides increased according to a quadratic function of irrigation timing, with the least colonization occurring at the 0-h timing. Colonization of pods treated with azoxystrobin was similar for all irrigation timings; whereas, suppression was greatest for tebuconazole at earlier irrigation timings. This study demonstrates that irrigation can be used to redistribute fungicides applied to peanut foliage to improve control of soilborne pathogens but administering irrigation within 24 h may decrease leaf spot control.
未到达目标生物的杀菌剂会导致病害防治效果降低。在美国东南部，叶面喷施杀菌剂常用于防治花生（落花生）病害。经常进行灌溉以冲洗施药叶片上的杀菌剂，从而最大程度地防治由土传病原菌引起的病害。在杀菌剂残留干燥之前进行灌溉可能会对叶面病害防治产生不利影响。2003年、2004年和2005年开展了一项小区试验，以评估不同灌溉时间后嘧菌酯、戊唑醇以及氟酰胺加百菌清的再分布情况。标准杀菌剂处理方案在施药后0、6、12、24、48或96小时接受1.3厘米的灌溉，并设置了不灌溉的对照。在进行灌溉处理时，未接受灌溉的小区进行覆盖。灌溉时间对每片叶子上早期叶斑病（花生尾孢菌）病斑数量有显著影响。在杀菌剂施药后立即进行灌溉时叶斑病更严重，在灌溉前延迟6小时和12小时叶斑病显著减少，而在灌溉延迟24小时或更晚时可获得最大防治效果。为了进一步量化杀菌剂残留分布，使用齐整小核菌对叶片和荚果进行生物测定。早期灌溉时间的小叶上病斑发展更严重，12小时及之后的时间病斑发展无差异，且总体上与未灌溉对照相似。所有杀菌剂处理的荚果定殖情况根据灌溉时间的二次函数增加，在0小时定殖最少。嘧菌酯处理的荚果在所有灌溉时间的定殖情况相似；而在早期灌溉时间，戊唑醇的抑制作用最大。本研究表明，灌溉可用于重新分布施用于花生叶片的杀菌剂，以改善对土传病原菌的防治，但在24小时内进行灌溉可能会降低叶斑病防治效果。
