Corn and soybean farmers were no strangers to white mold and ear rots during the 2009 growing season; but according to one Purdue University expert, there are measures growers can take to reduce the chances of a repeat in 2010.
“This year, with corn, the big story was ear rot at the end of the season,” says Kiersten Wise, Purdue Extension plant pathologist. “The most prevalent were Gibberella, Diplodia and Fusarium ear rots. Some of these ear rots cause major issues with grain quality because the fungi that cause them produce mycotoxins, or compounds toxic to livestock.
“In soybeans, the biggest issue was white mold, which was a problem during the growing season. This year, it caused significant yield losses in certain areas of Indiana."
Because the fungi that cause ear rots and white mold can survive on crop residue or in the soil from year to year, Wise said now is the time to start considering prevention methods for the 2010 growing season.
“The No. 1 thing growers can do to prevent ear rots or white mold is to select either a hybrid or a variety with some level of resistance to the disease,” she says. “Growers will want to take note of the disease problems they had this year and which hybrids or varieties they used, and maybe select a different hybrid with disease resistance to go into the field next time.
“In areas where white mold was a severe problem, soybean growers may consider using wider row spacing, such as 30-inch rows. Avoiding high plant populations and planting at recommended seeding rates also could help reduce the impact of white mold. The goal is to increase airflow and reduce high humidity within the canopy, which favors disease development.”
For corn growers looking for additional methods beyond corn hybrid selection, Wise suggests crop rotation and tillage practices. Since tillage will not be acceptable to no-tillers, rotating out of corn is likely the best option.
“Growers trying to manage ear rots in corn should rotate out of corn and break up residue with tillage if possible,” she says. “The fungi that cause ear rots survive in residue. Practices that encourage residue decomposition will reduce the risk of ear rots in the next corn crop.”
In addition to ear rots and white mold, many corn growers also experienced issues with gray leaf spot and northern corn leaf blight, and soybean producers again saw quite a bit of sudden death syndrome.
“Our best tactic to manage any disease would be choosing a resistant or more tolerant hybrid or variety,” Wise says. “With a few foliar diseases of corn and soybeans, there are other management options available, such as fungicide application. However, the decision to apply a fungicide should be made during the growing season.”
When farmers make their seed selections for the coming season, Wise says they should consider the history of each field to decide which resistant hybrids might best suit their needs.
“Choose hybrids based on field history,” she says. “If there are fields with a history of certain diseases, we recommend choosing hybrids or varieties with resistance to those diseases.
"Also, take into account production practices. If a grower is in a no-till or reduced-tillage, continuous-corn system, there is an increased risk of disease development, since many corn diseases survive from year to year in crop residue. We might recommend choosing a more defensive hybrid for those acres.”