Environmental Conditions in Soybean Diseases

— Written By and last updated by Nancie Mandeville
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close up image of cercospora leaf blight on soybean leaf

Today I would like to talk to you about a continuing conducive environment for diseases in soybeans and prevalent soybean seedling diseases. Early planting conditions were cool and wet and this has led to numerous reports of stands lost to dampening off pathogens.

Farmers have not yet planted soybeans should be mindful of the impacts of seedling diseases. Current conditions are warm and extremely wet and a lot of the regions of our County and these conditions favor pathogens like pythium, Phytophthora, and Rhizoctonia as well as fusarium. There are several options for reducing seedling disease which may include the use of seed treatments.

Choosing a chemical management strategies reliant on a good diagnosis and to make sure that the seed treatment includes active ingredients that are effective on the prevalent pathogen populations. For an accurate diagnosis of seedling disease pathogens please contact your local County agent here at the Union County Ag Center. Now disease considerations moving forward and as the growing season continues to be challenging with continued rainy conditions in most of the state or weather continues to be warmer and with these excessive wet conditions, we may be faced with several foliar diseases that could be yield-limiting.

Cercospora, frog eyed leaf spot, and Target spot maybe potentially yield-limiting if plants are affected between growth stages R3 and R5. Fungicides may be needed for susceptible varieties during that period of time. The further potential concern is soybean rust in late-planted soybean should weather patterns favor its movement and development. Currently, the closest report of soybean rust is in Hampton County, South Carolina. When a report of soybean rust is within a hundred miles of North Carolina soybean production announcements will be made to the NC State soybean portal and through the N.C. Cooperative Extension of Union County website. So scouting for foliar diseases especially during R3 and R5 growth stages may be particularly important this year to make foliar disease management decisions.

Root rot diseases like those caused by Fusarium and phytophthora may also be more severe given extended periods of saturated conditions. Make sure you scout regularly especially in areas with low lying fields in areas with high yield potential. Fungicides may be necessary as part of the disease management program this year due to weather conditions. Fungicide efficiency and efficacy are re-evaluated each year across the state and a joint fungicide efficacy table has been generated through the crop protection network. Again regular scouting will help to determine fungicide needs. So for more information on diseases of soybeans, there are several resources available is always don’t hesitate to contact your local Extension agent for any assistance.