小谷病: Management of Those More Common and Severe in Dry Years

2017年默瑟县的干旱. 摄影:NDSU

Managing 小麦 Streak Mosaic, Common Root Rot and Fusarium Crown Rot during drought.

2017年7月

安德鲁Friskop，谷物推广病理学家

在北达科他州干燥的土壤条件下，小谷物病害更为严重，包括小麦条纹花叶病和根腐病.  These two diseases add stress to the small grain plant, which is already under stress from lack of moisture and too much heat.  麦条花叶 is a viral disease primarily attacking wheat crops, 由小麦卷曲螨传播.  在北达科他州的小颗粒中最常见的两种根腐病是普通根腐病和镰刀菌冠和根腐病. 这些根腐病是由土壤传播的真菌引起的，这些真菌可以攻击小颗粒的根和冠.

麦条花叶: 麦条花叶 virus is carried from plant to plant by wheat curl mites.  小麦 curl mites are very tiny (1/100 inch in length).  Their population generally increases rapidly under extended warm dry weather, 而且螨虫数量也很高, the chance of infection of susceptible crops becomes higher.  螨虫在取食过程中传播病毒，病毒感染会导致叶子出现黄色条纹, 植物发育不良, 减少产量.  螨虫需要绿色的桥梁来生存，经常越冬在冬小麦或多年生草类杂草上, 然后在春季或初夏从这些植物转移到邻近的春季谷物.

螨虫在高温和干旱胁迫下更频繁地移动，寻找绿色、健康的植物组织. 它们移动到叶子的外缘，在那里它们的位置很容易在风中移动.  风把它们吹到邻近的植物或田地里，在那里螨虫再次传播病毒.  在干旱胁迫下，病毒病的严重程度更大，因为植物缺乏营养和水资源来补偿病毒感染.

麦条花叶管理: 麦条花叶 is managed by two cultural practices: elimination of wheat volunteer plants and 长满草的杂草 with herbicides (or tillage) at least two weeks prior to planting a new crop; and use of appropriate planting dates (see below).  Each practice helps to break the green bridge needed for mite survival.

消除志愿者和杂草: Glyphosate and paraquat may be used to destroy hosts of the mites and virus.  这应该在种植新作物到那片田地或邻近的田地前两周完成.  如果被感染的志愿者, 长满草的杂草, 甚至被感染的田地也没有被破坏, 它们可能是严重的感染源.   Glyphosate acts slower than paraquat in terminating grassy hosts, 这些植物上的螨虫在除草剂处理后的10天内会从受感染的志愿者体内移出.

种植日期: 冬小麦应该在9月中旬播种，北达科他州南部的郡县则更晚.  这减少了暴露于8月和9月初从受感染植物上分散的高螨种群的风险.  Green corn also may be an important reservoir for the mite and virus, 在玉米旁边种植冬小麦会增加螨虫从玉米转移到冬小麦的风险.  另一方面, 春小麦应尽早种植，以免在夏季螨虫积聚之前感染. Severe damage is most likely if the crop is infected at a young growth stage.

有关小麦条纹花叶病的更多信息，请参阅NDSU扩展通告PP-646小麦条纹花叶病。.

Common root rot and Fusarium crown and root rot management: Common root rot is caused by a soil-borne fungus, Bipolaris sorokiniana. 常见的根腐病真菌广泛存在于北达科他州的土壤中，造成小麦和大麦的根腐病.  Common root rot is characterized by a dark-brown discoloration of the roots, sub-crown节间, 通常是王冠.  The disease interferes with water uptake and subsequently affects grain fill.  潮湿的土壤和凉爽的温度通常允许小麦和大麦植物补偿受感染的根, and yield losses may not be noticed in a cool growing season.  然而, 如果植物随后暴露在高温和干燥的土壤中，根系的早期感染会导致严重的产量损失.  患病的根系不能吸收足够的水分

冠腐病和根腐病: 由镰刀菌属的几种真菌引起的根腐病可能与非常干燥的土壤或年降水量少的地区有关.  Fusarium root rot on wheat often is called dryland foot rot.  镰刀菌根腐病的特点是根和冠呈棕色到红棕色变色.  Affected plants may be in patches, appearing as prematurely ripened plants.  和普通根腐病一样, 感染镰刀菌根腐病的植株不能吸收足够的水分使植株通过灌浆.在这些压力条件下给植物浇水.

Management of common root rot and Fusarium crown and root rot防治小粒根腐病一般采用两种策略:轮作和种子处理.

轮作: 轮作是减少小麦小根腐烂风险的最有效方法.  非寄主作物包括阔叶作物，如大豆、油菜籽、干豆、亚麻和向日葵. If a small grain crop must be grown, oats tend to be less sensitive to root rot. Increasing the time between re-cropping wheat or barley also is effective; each additional year break from these two crops reduces the level of the fungus in the soil.

种子处理: 一些广谱注册的种子处理杀菌剂对小麦和大麦常见的根腐病真菌有抑制作用.  The most likely conditions where seed treatments would be beneficial are: under continuous wheat or barley production; short rotational cycles between wheat or barley; or in soils or areas where moisture stress is likely. Fungicide seed treatments will provide early-season protection from root rots. 然而, their residual should be viewed in terms of weeks, not months. 有关小麦和大麦种子处理的更多信息，请参阅NDSU推广通告PP-622 ND大田作物杀菌剂指南.