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Tips for dealing with wheat root rotBy Miles Dabovich Texas AgriLife Extension agent, agriculture, Wichita County Texas Recently, I attended some wheat field days. One thing I thought I would share from that is that we have had some root rot--primarily dry land root rot. When it comes to managing root rot, you're limited in your choices, primarily to cultural practices. Wheat root rots are caused by several different fungi that invade and colonize the roots and crown tissue of wheat seedlings and plants. In affected plants, the crown and root tissues have been destroyed and water and nutrient uptake has ceased. This is more apparent in years when high temperatures and drought occur around heading. Diseased plants prematurely appear as white headed areas long before expected normal times for maturation. An early indication of root rot infection is the observation of patches of light green or yellow plants during the spring. As the season progresses and wheat is exposed to drought and temperature stress, plants infected with root rot produce white heads that are either sterile or filled with shriveled grain. Key points: 1) Early planting of wheat (generally meaning before Oct. 15) favors a higher incidence of root rot and lower grain yields. This occurs because the early planting date provides a longer time for the root rot fungi to invade and colonize root and crown tissue. 2) A late planting date decreases the incidence of root rots because the root rot fungi have less time to invade and colonize root tissue. Fungi that cause wheat root rots infect many host plants and can survive on any plant residue in the soil. Hence, residue destruction helps control wheat root rots, but does not offer absolute control. Take-all of wheat, which is also a root rot, survives over the summer only on infected wheat residue. Hence, any practice that effectively eliminates infected residue also controls take-all. There are four basic types of root rot: --Pythium Root Rot: Characterized by patches of dead wheat seedlings that die either before or shortly after emergence. --Common Root Rot: Characterized by discoloration of the sub-crown intemode (two seedlings on the right), which is the tissue that connects the seed and seedling roots to the wheat seedling. --Sharp Eyespot: Also called Rhizonctonia root rot. Characterized by eyespots shaped lesions at the base of the tillers (stems). --Dryland Root Rot: Also called Fusarium root rot. Characterized by brownish discoloration of the roots and reddish-purple discoloration of sheaths. Wheat root rot management --Plant wheat late. Shortens the time root rot pathogens have to invade and colonize host plants. Destroy residue. Helps reduce inoculum level of root rot pathogens and is most effective with take-all. Maintain soil pH between 5.0 to 6.0. Mostly helpful in controlling take-all. --Rotate crops. Since root rot fungi survive on any residue, crop rotation has a minimal effect; again, most effective with controlling take-all. --Seed treatments. Although seed treatments provide excellent control of loose smut and common bunt, their value in controlling root rots is less clear. Seed treatments generally facilitate emergence and stand establishment; however, no compound controls all of the root rots. Harvesters will soon begin harvesting wheat in the area and, other than a little root rot, it has been a great year for diseases and insects. The biggest problem was the dry fall during planting season, causing some of our crops to be a little thin. But, with timely rains we had in February, it's a lot better than it could of been. If I had to make a guess at the average yield in the county, I would say somewhere between 25 to 30 bushels which is about an average crop, at best. Whatever it is, let's all pray for a good harvest so that we can get it out of the fields and to the elevators. 5/26/08 Date: 5/22/08
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