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Morning Sun
  • STITES: Controlling fungal diseases in wheat

  • Wheat is a dry-weather crop and has a pretty minimal need for water to produce well compared to most other crops raised in this area.  Unfortunately, wheat is not a good wet-weather crop, and does poorly when excessively wet conditions prevail.  Another unfortunate thing is that southeast Kansas is a wet-weather region, so producing good, high-quality, high-yielding wheat in our area is very difficult.

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  • Wheat is a dry-weather crop and has a pretty minimal need for water to produce well compared to most other crops raised in this area.  Unfortunately, wheat is not a good wet-weather crop, and does poorly when excessively wet conditions prevail.  Another unfortunate thing is that southeast Kansas is a wet-weather region, so producing good, high-quality, high-yielding wheat in our area is very difficult.
    As we know, our wheat gets bombarded with fungal diseases every year.  Those diseases that cause problems include leaf rust, speckled leaf blotch, glume blotch, powdery mildew, scab and stripe rust.  There are others that occur on an infrequent basis, as well. When you put all of these problems together, it can add up to severe yield losses.
     It has been proven that a fungicide can increase yields significantly in certain years on susceptible varieties. Remember, there is a large variation in disease resistance in wheat varieties.  Whether wheat responds favorably to a fungicide is mostly a result of the wheat variety and weather patterns during the spring.  If it is cool and wet between April 15 and May 15, then it is likely that we will have a disease problem and a fungicide would be likely to improve the yield significantly. On the other hand, if the weather is dry and warm, disease pressure is likely to be low and a fungicide probably would not result in a significant increase.  It should be noted that none of the fungicides will have any affect on barley yellow dwarf because this disease is caused by a virus rather than a fungus.
    There are two main types of fungicides available and several mixed products containing both of these classes of fungicide.  The triozole fungicides include Alto, Caramba, Tilt, Proline, Folicur and Prosaro.  The strobilurin fungicides include Quadris, Evito and Headline.  The package mixed materials containing both of these classes of materials include TwinLine, Quilt, Quilt Xcel, Stratego and Absolute. Both of these do have some systemic action but are not really translocated from one leaf to another.  The triazoles do have some curative ability but that is somewhat limited.  Some of the products labeled may also be available in  generic brands that should be less expensive so it would pay to shop a little to find those chemicals at a cheaper price.
    Most of these chemicals will work on the most troublesome fungal pathogens we are faced with in this area.  The top three problems probably should include leaf rust, stripe rust and scab.  Scab is probably the hardest to control. Of course, there are other troublesome diseases ,as well, which would usually be controlled with an application of one of these chemicals.
    For foliar diseases, the product label on most of these materials states that the optimum time for application is between 50 percent and full emergence of the flag leaf.  However, this may not be the best timing because disease pressure may not have developed by this time.
    Page 2 of 3 - Most of these products will remain in the plant for several weeks, but will not remain effective through the whole filling and maturation phase of the wheat.  Therefore, it is extremely important to apply the fungicide at the proper time rather than too early.  
    It should be noted that it can also be applied too late, which could result in reduced control or a violation of the harvest restriction on the treated wheat. If there is a lack of disease pressure, spraying should be delayed and the wheat could be sprayed later when disease pressure becomes evident.  When you decide to spray, be sure to use a chemical that is labeled for that stage of wheat development.  Remember that all of these products have a post harvest interval that must be observed in order to avoid residue problems.
    The rate of material applied is going to vary from product to product.  If there is a range of rates, it would probably be best to use the highest recommended rate considering the amount of disease pressure that wheat is subjected to in our area.  Be sure to read and understand the application directions in order to get the best disease control and also to avoid having illegal residue levels at harvest time.
    One disease that does not appear on most of the fungicide labels is fusarium head blight, which is more commonly known as head scab.  This is something we deal with almost every year. This disease is caused by a fusarium fungus.  Infection occurs after heading when the head begins to flower.  The spores are unable to germinate unless there is free moisture on the head, so scab is likely to be a problem when there are continued wet conditions during wheat flowering.  That’s every year in southeast Kansas. The chemical must be applied before the spores have a chance to land and germinate.  This means spraying after the head emerges and during the early flowering stage.  There are no chemicals that claim more than just suppression of this disease. Correct timing of application is extremely critical.
    There are seveal chemicals  labeled for suppression scab.  Efficacy ratings done by Erick DeWolfe, K-State wheat disease specialist, indicates that Metconazole (Caramba) and Prothioconazole (Proline)have worked the best in scab control. There is also a package mix of two chemicals including Prothioconazole (Proline) and Tebuconazole (Folicur) that is being marketed as Prosaro. Erick’s work indicates that this also does a good job. Once again, the label on all scab labeled products says suppression rather than control.
    The Caramba label states that it should be sprayed at the beginning of flowering.  The Proline label states that it should be applied when no less than 75 percent of the heads are emerged but no later than 50 percent bloom.
    The Prosaro label states that it should be applied at early flowering.  Whatever the case, the need to read the label before use cannot be overstated.
    Page 3 of 3 - So in closing, all of the chemicals listed will control the main diseases including leaf rust, stripe rust, speckled leaf blotch, tan spot, and powdery mildew.  There is a pretty wide spread of prices so that this could be one of the factors in deciding which material to use.
    If you have specific questions about any of the fungicides and their use in controlling wheat diseases, give me a call at the Extension office at 724-8233.

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