Schillinger W F, Paulitz T C
Department of Crop and Soil Sciences, Washington State University, Dryland Research Station, Lind 99341.
Root Disease and Biological Control Unit, United States Department of Agriculture-Agricultural Research Service, Pullman, WA 99164.
Plant Dis. 2014 Mar;98(3):389-394. doi: 10.1094/PDIS-04-13-0420-RE.
The soilborne fungus Rhizoctonia solani AG-8 is a major concern for farmers who practice no-till in the inland Pacific Northwest of the United States. Bare patches caused by Rhizoctonia spp. first appeared in 1999 during year 3 of a 15-year no-till cropping systems experiment near Ritzville, WA (269 mm of annual precipitation). The extent and pattern of patches were mapped each year from 1999 to 2012 at the 8-ha study site with a backpack-mounted global positioning system equipped with mapping software. Bare patches appeared in winter and spring wheat (SW; Triticum aestivum), spring barley (SB; Hordeum vulgare), yellow mustard (Brassica hirta), and safflower (Carthamus tinctorius). At its peak in years 5 to 7, bare patches occupied as much as 18% of total plot area in continuous annual monoculture SW. The area of bare patches began to decline in year 8 and reached near zero levels by year 11. No measurable patches were present in years 12 to 15. Patch area was significantly greater in continuous SW compared with SW grown in a 2-year rotation with SB. Additionally, the 15-year average grain yield for SW in rotation with SB was significantly greater than for continuous SW. Russian thistle (Salsola tragus), a troublesome broadleaf weed with a fast-growing tap root, was the only plant that grew within patches. This article reports the first direct evidence of natural suppression of Rhizoctonia bare patch with long-term no-till in North America. This suppression also developed in a rotation that contained broadleaf crops (yellow mustard and safflower) in all but 5 years of the study, and the suppression was maintained when safflower was added back to the rotation.
土壤传播的真菌立枯丝核菌AG-8是美国太平洋西北部内陆地区采用免耕法的农民主要关注的问题。立枯丝核菌属造成的光秃斑块于1999年首次出现，当时是在华盛顿州里茨维尔附近进行的一项为期15年的免耕种植系统试验的第3年（年降水量269毫米）。1999年至2012年期间，每年在这个8公顷的研究地点，使用配备绘图软件的背负式全球定位系统绘制斑块的范围和分布模式。光秃斑块出现在冬小麦（SW；普通小麦）、春大麦（SB；大麦）、黄芥（芥菜）和红花（红花）中。在第5至7年达到峰值时，连续单作冬小麦中光秃斑块占据了总试验区面积的18%。光秃斑块的面积在第8年开始下降，到第11年接近零水平。在第12至15年没有可测量的斑块。与与春大麦轮作两年种植的冬小麦相比，连续种植冬小麦时的斑块面积显著更大。此外，与春大麦轮作的冬小麦15年平均谷物产量显著高于连续种植的冬小麦。刺沙蓬（刺沙蓬）是一种麻烦的阔叶杂草，主根生长迅速，是唯一在斑块内生长的植物。本文报告了北美首次通过长期免耕对立枯丝核菌光秃斑块进行自然抑制的直接证据。这种抑制作用也在一个轮作体系中出现，该轮作体系除了研究的5年外，其他年份都包含阔叶作物（黄芥和红花），并且当红花重新加入轮作时，这种抑制作用得以维持。
