WOOSTER, Ohio -- Proline may be the most effective fungicide on the market to suppress head scab on wheat, but for the product to be the most effective, careful risk assessment, timing of application, and proper application techniques are critical.
Proline, from Bayer CropScience, is the newest fungicide available to farmers that controls a wide variety of crop diseases, including head scab. Head scab is a serious wheat disease that attacks the plant during flowering under moist conditions. The disease infects the wheat heads, causing shrunken, lightweight kernels, thereby reducing the quality and feeding value of the grain. The fungus that causes the disease also produces a chemical in the infected grain called vomitoxin that is toxic to livestock and humans.
"Proline is the best we've seen so far in terms of head scab control and vomitoxin reduction," said Pierce Paul, an Ohio State University plant pathologist with the Ohio Agricultural Research and Development Center. "That being said, it's not 100 percent effective, especially on susceptible varieties. Proline works best on resistant varieties exhibiting moderate disease levels. On average, between 35 percent and 50 percent scab reduction and between 30 percent and 45 percent vomitoxin reduction can be achieved if Proline is applied at the right time using the correct application technology."
To get the most out of Proline efficiently and economically, Paul offers the following management recommendations:
• Use the Wheat Fusarium Head Blight Prediction Center (http://www.wheatscab.psu.edu) as a guide to assess head scab risk and determine when to spray if warranted. "The trick to head scab control is knowing when head scab might be a threat, and your best guess is the risk assessment model," said Paul, who also holds an OSU Extension appointment. "Applications are made at flowering before any visual symptoms are seen on the plant. If the application timing is off, the fungicide will be less effective, and you're just wasting your money." Paul said that dried anthers hanging from the spikes on the plant head indicates that the flowering period has passed.
• Use the right application technology. One such technology is correct droplet size. Application should be made using fine to medium-sized droplets (300-350 microns) using a flat-fan nozzle. "You need to get the fungicide on the head, and research has shown that this is the best method for achieving that," said Paul. "It allows an even distribution of the product, while minimizing spray drift."
• Pay attention to nozzle orientation. "Normally a nozzle is pointed vertically, but when dealing with head scab control the nozzle should be angled 30-45 degrees down from horizontal," said Paul.
• Apply Proline at 10 to 20 gallons per acre for the most effective head scab control.
• Position the nozzle 8 to 10 inches above the heads of the plants.
Ohio's wheat crop is now beginning to flower, and is expected to continue across the state over the next few weeks. According to the Wheat Fusarium Head Blight forecasting model, the risk for head scab development is low. However, the prediction is based on cooler temperatures the state experienced several days ago. It has since become considerably warmer, and a forecast of rain over the Memorial Day holiday will increase the threat for head scab.
"Now is the time for growers to start keeping their eyes on the scab risk assessment tool for frequent updates," said Paul. "Head scab spores are being produced in the fields. All we need is the right conditions for the disease to develop."
For more information on the progress of the wheat crop, or for updates on head scab, log on to Ohio State University's Agronomic Crops Team Web site at http://agcrops.osu.edu.