Crop Scene Investigation - 59 Solved: The white mould mystery in Mike's soybean field

Tuesday, February 9, 2016

White mould infested the burned portion of Mike's soybean field because the fire removed corn residue. The lack of residue led to warmer soil which, in turn, created earlier emergence and faster nodulation. This caused the soybeans to grow rapidly and produced perfect conditions for the disease to prosper.

When DuPont Pioneer agronomist Scott Fife saw a picture of Mike's soybean field from 300 feet above, it confirmed his suspicions. The photo from an unmanned aerial vehicle (UAV) showed the white mould in Mike's field was confined to the area where a spring fire had removed the corn residue.

"Basically, Mike planted into two separate environments in the same field," explains Fife. "The residue-covered portion was your typical no-till field where the soil warms up more slowly and you don't get that quick start early in the spring."

Mike ran into trouble in the burned portion of the field because, with the residue removed, the soybean plants grew much faster, producing a taller, lusher plant with a much denser canopy that closed quickly. This combined with hot, humid weather to produce ideal white mould conditions.

"In the photo you can see that the crop in the burned area is changing colour on Sept. 1. It's obviously more mature and that early growth set the stage for Mike's trouble," explains Fife. The best looking soybean fields often get white mould."

Fife says UAVs are a welcome addition to the agronomist's toolbox. "You still have to get your boots dirty, but the ability to fly over the field really helps.

"One of the biggest things we can see from above is the nitrogen status of corn," says Fife. "Just a slight change in colour from green to yellow can indicate nitrogen deficiency. You may not see it walking through a field, but it's really visible from the air."

Congratulations to: Bryan Cook, a CCA from Spencerville in eastern Ont., for his correct answer. Bryan notes white mould has been especially noticeable in his part of the province for the past two years. BF