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Green and growing
By Bruce Bosley Extension Agent/Cropping Systems Many farmers are reporting poor grainfill in areas of their dryland or irrigated fields this July. The fields I've been in have normally shown drought stress as the primary cause of the problem in these areas, but I've seen a few instances of dryland foot rot and one instance of Take-All in an irrigated wheat field. Knowing a little about diseases and what causes them helps to plan taking steps to avoid them. Take-All is a disease of autumn-seeded wheat. It is normally rare in Colorado but can occur with irrigation, especially center-pivot when the moisture is plentiful. Diseased stems are weakened at their base, causing them to lean and fall non-directionally. Take-All is most common where wheat is continuously cropped. Completely white heads on plants with a shiny black lower stem is indicative of take-all. Take-all is most active during the cooler spring soil temperatures. This pathogen becomes inactive during hot and dry conditions. Soil conditions that favor the pathogen include: neutral to alkaline soils, especially those deficient in nitrogen and/or phosphorus, poorly drained soils. Continuous cropping of wheat significantly favors the pathogen. The sudden development and appearance of whiteheads after a period of hot, dry weather gives the impression that the disease develops late in the season and that disease development is favored by hot, dry conditions. However, pathogen activity is actually favored by cooler temperatures earlier in the growing season, and later occurring hot, dry weather accelerates the water stress and premature ripening. No wheat or barley cultivars are resistant to infection by the Take-All fungus. Crop rotation is the best way to control Take-All; usually a one-year break from wheat and/or barley is sufficient to reduce soil borne inoculum to inconsequential levels. Tillage can be helpful in the management of the take all fungus by fragmenting and hastening the decomposition of the infested residue. However, there are reports that Take-All can be less severe in fields maintained as no-till, where wheat is direct seeded. Dryland foot rot (Fusarium Crown Rot) is a yield robbing disease that impacts winter wheat on the driest areas of dryland fields. Like Take-All, dryland foot rot is found in field patches causing white premature maturing heads with severely reduced grainfill. Dryland foot rot causes a browning of the wheat crowns and lower stems (not-black). Dryland foot rot is sometimes recognized when the wheat stems and heads turn yellow earlier in the spring resulting in spindly plants with small heads. Symptoms are usually more acute on south side-slopes and knobs, generally related to water stress. Dryland foot rot survives in wheat residues. Its incidence has been increasing with reduced tillage practices. However it is most prevalent on soils that are both loose and dry so managing for higher soil moisture as well as good plant growth are both beneficial. The first step in avoiding these diseases is to rotate. Broadleaf crops are best for dryland foot rot but oats, corn, millet, and broad-leafed crops are all suitable for Take-All. Providing good fertility management and proper planting conditions are the next best steps to take for both diseases. Seed treatments are effective in reducing dryland foot rot. Please contact me, Bruce Bosley about these or other cropping systems or natural resource topics at 522-3200, extension 285 in Sterling or 542-3540 in Fort Morgan. Date: 8/2/07
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