Scouting fields for plant diseases is a simple way to maximize profits and yields over time. Scouting allows growers to assess stand losses early and replant as needed, determine what diseases are active and their potential to damage the crop at key growth stages, obtain historical data on common disease issues in fields, determine if fields require an early harvest, make timely fungicide applications or avoid applying fungicides unnecessarily. The following are some techniques to scout small grains for diseases and some common diseases that you may see in your fields.
To scout small grains first estimate the size of your field. A good rule of thumb I use is to scout 1-2 sites per acre of field. Ensure that each site you choose in a field is chosen AT RANDOM, that is, without bias. A protocol for randomly choosing sites in a field can be found by following this link: http://www2.ca.uky.edu/entomology/entfacts/entfactpdf/ef113.pdf. At each site you will scout a circular area 10-15 feet in diameter. Within each circular area note any issues with stand, health, etc. Select 25-50 plants at each site and assess for disease. A 10x hand lens is often required to visualize signs (the pathogen, its parts, or products) of most plant disease causing agents. The entire plant should be assessed. Fields should be scouted approximately every 2 weeks until harvest and perhaps more if the weather is wet and humid.
Diseases that may start to develop or show symptoms early (jointing and later) include viruses, powdery mildew, leaf blotches, and root rots.
Diseases that tend to show up around flag leaf include rusts and the occasional smut
Diseases that tend to occur around flowering include Fusarium head blight, Stagonospora glume blotch, and eyespot.
Keep in mind that many plant diseases cannot be positively identified without the help of a plant diagnostic lab. Improperly diagnosed diseases can result in severe crop losses or unnecessary pesticide applications. If you have diseased plants and need help with disease identification send samples (placed in plastic bags with a piece of moist paper towel) to the University of Delaware Plant Diagnostic Clinic located at Townsend hall in Newark, Delaware. Your local county agent can assist you in submitting samples to the clinic.
Scouting takes time and effort, as well as attention to detail. However, this effort pays in the long run with increased yields and profit.