Corn+Soybean Digest
2016 Soybean outlook: Diseases and insects

2016 Soybean outlook: Diseases and insects

Think Different Talk with your agronomist to identify fields that contained diseases in 2015 and choose soybean varieties that will offer optimal control for the new season. Put offensive soybean varieties in areas you can keep clean and that have no history of disease. Be ready to start scouting in spring to see where diseases might be lurking, particularly in no-till fields. Know which varieties are susceptible to disease and those that respond best to fungicide application. Then be ready to apply fungicides and insecticides when needed. Consider all the angles before cutting back on insect or disease management. Cost per bushel produced drives profitability, not necessarily cost per acre.

The excessive rainfall events that occur with greater frequency in spring and summer should push farmers to scout more closely in 2016 for disease and insects to save every bushel.

Farmers saw few soybean insects during a cool and wet 2015 growing season. “But the wet season triggered development of soybean diseases,” says John Smith, WinField agronomist from Ashville, Ohio. “Root and stem diseases, including Phytophthora, sudden death syndrome (SDS) and white mold, caused damage in soybean fields across the state. Farmers who planned ahead for disease management, using variety selection and control measures, were able to reduce incidence and yield loss caused by those diseases.”

We asked WinField agronomists from seven Midwest states, as well as some university entomologists/plant pathologists, to give us their take on 2015 challenges, and an outlook for 2016.


Download the 2016 Soybean outlook: Diseases and insects in .PDF format.
This file type includes high resolution disease and insect images, as well as a scouting calendar.

Disease and insect challenges

2015 soybean diseases

Seedling diseases, such as Phytophthora, Rhizoctonia, Pythium and Fusarium, were mentioned as problems by agronomists in numerous states. Fortunately, many farmers are using seed treatments for proactive control of these diseases.

Kevin Sloane, regional technical seed manager from Viroqua, Wisc., recommends that farmers continue this practice. “Some farmers cut seed treatments to save on costs, but keeping them will give you a much greater return on investment and offer early protection.”

The other challenge when seedling diseases hit early is greater chance of sudden death syndrome (SDS) occuring later in the season, says Ryan Wolf, WinField agronomist from Sheldon, Iowa. He recommends Warden CX as a top seed treatment for Phytophthora, Pythium and Fusarium; and says Ilevo is a good alternative for SDS control.


Download the 2016 Soybean outlook: Diseases and insects in .PDF format.
This file type includes high resolution disease and insect images, as well as a scouting calendar.

Foliar diseases were a larger problem as summer rains created ideal conditions in areas of many Midwest states. Agronomists and plant pathologists in South Dakota, Minnesota, Wisconsin and Illinois highlighted white mold as a serious issue.

“Cool, wet weather combined with heavy morning fogs and low spots resulted in notoriously high infestations of soybean white mold from Decatur on north in 2015,” says Bob Beck, WinField agronomist, Chatham, Ill. Some fields with susceptible varieties saw pretty significant yield losses. However, warmer weather in southern Illinois prohibited the disease from taking as large a toll, he added.

Sloane says Wisconsin saw more pressure from white mold in 2015 than they have in the past four years. Trait selection is the most important factor to consider when managing white mold, he says.

“Planting management can also help, but most Wisconsin farmers already plant wider rows and reduced populations to allow more air circulation within the canopy to help avoid losses due to white mold. Other control options are available, but they add to input costs, and fungicide efficacy data is limited and inconsistent, he adds. “That makes genetic selection the best option for us.”

Other foliar diseases mentioned causing some issues in 2015 were frogeye leaf spot in Indiana and southern Ohio; and SDS, brown stem rot and charcoal rot in Illinois.

“Soybeans suffered from too much water early in the season,” says George Watters, WinField agronomy manager from Noblesville, Ind. “Rain events and heavy dews created an environment that was favorable to foliar diseases, including frogeye leaf spot, Cercospora leaf spot and Septoria brown spot.” Frogeye is a serious yield-limiting disease, but farmers who scouted and treated for it and other diseases as they developed had good yield response from plant health fungicide applications, he reports.

2015 insect challenges

Very few soybean insect issues occurred in 2015. Aphids did wreak some havoc in Minnesota, says Jon Zuk, WinField agronomist from Hayfield. “Farmers who had the greatest success controlling aphids were those who scouted diligently and acted quickly when increased populations constituted a yield threat.”

Stinkbugs in southern Indiana and bean leaf beetles in western Indiana became significant foliar and pod feeders as the summer progressed, according to Watters. “Farmers who added insecticides to their plant health treatments generally saw favorable responses.”

 

2016 outlook

Farmers should talk with their agronomists to identify fields that contained diseases in 2015 and choose soybean varieties that will offer optimal control for the new season, advises Beck. “Put offensive soybean varieties in areas you can keep clean and that have no history of disease,” he says. “Be ready to start scouting in spring to see where diseases might be lurking, particularly in no-till fields.”

He recommends knowing which varieties are susceptible to disease and those that respond best to fungicide application. “Then be ready to apply fungicides and insecticides as needed,” Beck says.

For fields with a history of SDS, Bayer Ilevo soybean seed treatment is a new product that shows promise. If conditions are favorable, frogeye leaf spot infection may be an even bigger issue for Ohio soybean growers in 2016, Smith adds.

Foliar fungicide use on soybeans showed an average return of 2.1 more bushels per acre in 2015 WinField Answer Plot trials across the Midwest. However, due to a large range of response seen – from minus 6 bushels to plus 8.2 extra bushels – agronomist Sloane emphasizes that planning on a field-by-field basis will be essential to optimize return on investment.


Download the 2016 Soybean outlook: Diseases and insects in .PDF format.
This file type includes high resolution disease and insect images, as well as a scouting calendar.

Aphids are expected to be the primary soybean pest in southeastern Minnesota again in 2016, Zuk predicts. Other insects to watch for include the bean leaf beetle, especially early in the season.

Diligent scouting can help discover insect and disease problems early, but fast action is critical. “Anybody can scout,” Ryan cautions, “but making the decision to pull the trigger to do something if you find a problem is probably the biggest factor in protecting yield potential.”

Watch cost-per-bushel economics

Watters encourages farmers to consider all the angles before cutting back on insect, disease or weed management. “Cost per bushel produced drives profitability, not necessarily cost per acre,” he says. “Work with your local agronomist to make the right input investments. Anyone can find places to cut, but make sure you cut the right things and keep those that will still benefit your operation.”

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