“Root health" is a term that plant pathologists have used for many years to describe a plant root that has very little disease. Most of the time these studies have focused on specific diseases, such as Pythium or Fusarium root rot. But, in the field there is always a combination of diseases, and they are affected by the environment. There have been numerous rating systems, but it has been difficult to correlate root ratings to yield. Environment makes a major impact on which diseases are limiting yield. For example, in cool, wet soils, Pythium may be the major problem, while in dry, sandy soils, other pathogens are most important.
Years ago I started classifying pathogens into two main groups, killers and nibblers. The killers can kill the plant before or shortly after it emerges, thereby affecting harvest population. The nibblers, both fungi and nematodes, reduce the number of small fibrous roots that affect water and nutrient uptake. There may not be any visible symptoms from the nibblers, except a reduction in yield. These are the “hidden" diseases.
When available, genetic resistance is the main choice for disease control. However, for many soilborne diseases there aren’t any sources of resistance. A second control strategy is crop rotation, but many pathogens have wide host ranges and affect wheat, corn, soybean and many other crops. One of the most exciting areas for control of soilborne diseases is the new systemic seed treatments. While they do not provide season-long control, they allow the plant to establish a healthy root system.
As the prices of commodities have increased, growers are trying to increase yields. We know the genetic potential of wheat varieties is never achieved, so researchers are trying to determine what is limiting yield. Our research over the past several years has demonstrated that improved root health and less damage by the root nibblers are major factors in limiting crop yields.
For more information visit www.farmassist.com or call the Syngenta Customer Center at 866-SYNGENTA (866-796-4368).
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