Spring 2016 field crop disease issues update for southwest Michigan
Common diseases in wheat, corn and soybean in southwest Michigan, how to manage them, and the likelihood of their prevalence this year.
Diseases of field crops are typically dependent on weather conditions at key stages in plant development, the presence of susceptible varieties/hybrids and the prevalence of pathogens either overwintering in the field or brought in from regions where they do overwinter – sometimes referred to as the disease triangle. Michigan State University plant pathologist Martin Chilvers addressed the significance of these factors in wheat this spring and discussed the possibilities of disease occurrence in corn and soybean at a St. Joseph County IPM (integrated pest management) breakfast meeting on June 7, 2016.
One of the major disease issues so far this spring has been the early and vigorous spread of stripe rust on wheat. This problem has been described in earlier MSU Extension articles: “Wheat stripe rust moving up the plant in southwest Michigan fields,” “Scout for stripe rust and other wheat leaf diseases now,” “New ratings of wheat varieties for stripe rust” and “Managing wheat leaf diseases and Fusarium head blight (head scab).” Stripe rust is favored by cool nights of less than 60 degrees Fahrenheit, which were prevalent throughout much of Michigan during mid-spring.
Farmers should assess whether a foliar fungicide prior to the more typical timing for head scab during wheat flowering is economically sound. The best timing for fungicide applications for head scab is four days after 50 percent of plants are flowering. The Fusarium Risk Assessment Tool is available to assess the potential for severe infestations, but Chilvers warned that farmers should use the tool as a guide but consider factors such as variety susceptibility and disease history in making a decision to spray. He stressed that the best management tools in a farmer’s tool belt are: choosing resistant varieties; timely applications of fungicide that are effective against the given pathogen; good rotation decisions (e.g., don’t go from wheat into wheat or corn); and avoid irrigating during flowering.
The common corn diseases in southern Michigan are typically northern corn leaf blight, gray leaf spot and common rust. Though it is early in the season, Chilvers again stressed the importance of scouting fields, particularly for hybrids or inbreds (parent lines) that are more susceptible. He also referred to recent observations of Goss’s wilt in northern Indiana and southern Michigan. This can be spread by seed (evident as patches in a field) or dispersed by wind (spreading from field margins downwind of infected fields). Symptoms include water-soaked patches on leaves with freckling around the margins of the lesions. He also mentioned that corn rust diseases have been problematic in southern regions of the U.S., and although most of these diseases are not common in Michigan, it would be worth keeping an eye out for rusts as the season progresses.
Two of the main diseases of soybean common in southwest Michigan are white mold and sudden death syndrome. Chilvers explained that white mold levels can be heightened when rain or irrigation occur during flowering, so watering less frequently with greater volumes is recommended if white mold has been a problem in a field. Further discussion and recommendations have been highlighted in the following MSU Extension articles: “White mold of soybeans and foliar fungicides,” “Managing white mold in soybeans in Great Lakes region” and “Begin managing white mold in soybeans this spring.” However, he noted that such practices may actually exacerbate sudden death syndrome occurrence, which favors saturated soils, so farmers will need to assess the risks of infestations of each of these diseases. For more information, see “Soybean sudden death syndrome confirmed in two new counties, Lapeer and Isabella” and “Soybean sudden death syndrome continues to spread across southwest Michigan” by MSU Extension.
The St. Joseph County IPM Breakfast Series is organized by the MSU Extension field crops team in southwest Michigan. The meetings run through the end of June and are held on Tuesdays at the Royal Café in Centreville, Michigan, beginning at 7 a.m. Each meeting includes an update of the major field crops grown in the region, including a crop and pest report, followed by a presentation from a guest speaker on a topic important to crop production. Participants can order breakfast and eat during the meeting.
The speaker for June 14 will be Tom Shibley with Midwest BioAg, who will address the topic, “Soil Health: Feeding the Soil.” The meeting will be sponsored by the Monsanto Company, and CEU and RUP credits will be available. Meetings are open to the public. For more information on this breakfast meeting series, contact Eric Anderson at the MSU Extension St. Joseph County office at 269-467-5511.