Potential use of fresh mulch to curb potato late blight epidemics in Brazil

ABSTRACT Field experiments were conducted during spring 2014 and fall and spring 2015 to determine the effect of fresh mulch on the development of Phytophthora infestans epidemics, in Lapa Municipality, Parana State, southern Brazil. The used cultivars were ‘Agata’, susceptible, and ‘BRS Ana’, moderately susceptible. The main treatment consisted in manually applying a 10cm-thick layer of fresh mulch when potato sprouts were emerging. Fresh mulch was prepared with plants available at that time of the year. For the spring experiments, fresh mulch was a mixture of oats, rye grass and wild radish (60 t/ha) and for the fall experiment, semi-ripe elephant grass (90 t/ha). Plots consisted of six 10m-long rows, spaced at 0.8m, containing 28 plants per row. Experimental design was in completely randomized blocks with four replicates. Natural inoculum was adopted. Percentage of leaf area was weekly estimated until the end of the plant cycle and the area under the disease progress curve (AUDPC) was calculated. Application of fresh mulch significantly reduced AUDPC by 32.1%, 12.4% and 23.1%, compared to control in all seasons, for ‘BRS Ana’ and by 26.1%, 2.8% and 12.0% for ‘Agata’. Application of fresh mulch showed to be a promising practice for the integrated management of late blight and for the protection of yields, especially in periods more favorable to the development of the disease. More detailed studies should be conducted on the plant type and amount of fresh mulch to be used, as well as on the possibility of reducing concentrations or increasing intervals between fungicide sprays.

摘要 本研究于巴西南部巴拉那州拉帕市，2014年春季及2015年春秋两季开展田间试验，旨在明确新鲜覆盖物对致病疫霉（Phytophthora infestans）引发的马铃薯晚疫病流行的影响。供试品种包括易感品种‘Agata’与中感品种‘BRS Ana’。核心处理措施为在马铃薯出苗阶段，人工铺设厚度为10厘米的新鲜覆盖物，覆盖物原料采用试验当季可获取的植物：其中春季试验所用覆盖物为燕麦、黑麦草与野萝卜的混合物，施用量为60 t/ha；秋季试验则采用半成熟象草，施用量为90 t/ha。试验小区设置为6行长10米、行距0.8米的种植带，每行长种植28株马铃薯。试验采用完全随机区组设计，设置4次重复，采用自然菌源，未进行人工接种。每周估算叶片病斑面积占比，直至作物生育期结束，并计算病情进展曲线下面积（Area Under the Disease Progress Curve, AUDPC）。结果表明，相较于对照组，所有试验季候下施用新鲜覆盖物均可显著降低AUDPC：其中‘BRS Ana’的降幅分别为32.1%、12.4%与23.1%，‘Agata’的降幅分别为26.1%、2.8%与12.0%。研究显示，施用新鲜覆盖物是马铃薯晚疫病综合防控与产量保障的极具应用前景的措施，尤其在病害更易发生的时期。后续需针对覆盖物种类、施用量，以及降低杀菌剂施用浓度或增加施药间隔的可行性开展更为细致的研究。