The 2011 planting season has not gone smoothly for many Indiana producers, with only 25 percent of the intended soybean acreage in the ground as of Friday, June 3 (USDA NASS). This puts the Indiana soybean crop about 2-3 weeks behind the average development schedule, and there are questions about if this year’s soybean crop is at greater risk for soybean rust due to the late planting. June planted soybeans will be at a younger growth stage and possibly at risk for yield loss from soybean rust should spores of the fungus that causes soybean rust (Phakopsora pachyrhizi) reach Indiana in August or September. However, the likelihood that disease will establish and cause yield loss in Indiana in 2011 depends on many factors, including weather patterns and the level of disease that develops throughout the year in the southern U.S.
Soybean rust has been slow to develop in the U.S. in 2011 due to drought conditions in most southern states (Figure 1). This means that there is currently a low amount of diseased kudzu that can serve as source of spores for soybean infection and the northward movement of the disease. Weather conditions will dictate how quickly the disease progresses in southern states, and sentinel plots are established in these areas to monitor the movement of the disease. Indiana also has soybean plots that can be observed for soybean rust should the disease move north at a critical point in the growing season. Since soybean rust was first discovered in the U.S. in 2004, Indiana and much of the Midwest have been spared from soybean rust outbreaks that could result in yield loss due to the late northward movement and development of the disease. However, producers that are concerned about soybean rust have several options to stay informed of the risk of soybean rust in Indiana:
1. Soybean rust development can be tracked using the ipmPIPE Web site. Observations of soybean diseases and fungicide spray advisories specific to Indiana can be accessed by selecting the outline of the state of Indiana on the national map.
2. Indiana soybean producers can subscribe to the Indiana soybean disease update list serve. This email alert service will provide convenient and timely updates on soybean disease monitoring in Indiana, and also provide information on fungicide spray applications if soybean rust reaches Indiana at a critical time during the growing season.
3. Purdue University will continue to maintain a toll-free soybean disease hotline, which is updated weekly beginning in late June. The phone number is 866-458-RUST (7878).
4. Updated commentary on the risk of soybean rust and other soybean diseases will be released in the Pest and Crop newsletter as the season develops.