There may not be much corn growers can do to prevent the spread of ear molds and mycotoxins if weather conditions are right for development, as was the case in 2009. However, there are some production practices they can follow to help reduce the risk.
Ear molds, like Gibberella ear rot that significantly impacted Ohio's corn crop last year, have a nasty habit of sticking around on stalk residue, whether it's corn, soybeans or wheat, and can even reside on corn kernels and cobs left in a field.
"Short of complete tillage, shredding stalks and some light tillage after harvest will help promote residue decomposition and reduce disease inoculum, " says Peter Thomison, an Ohio State University Extension corn agronomist.
As corn growers prepare for this year's growing season, Thomison offers additional tips for reducing the risk of ear mold and mycotoxin development:
• Don't plant corn after corn or after wheat, especially in a no-till situation. Both crops are a host for the fungus and the grower is taking a chance of exposing the crop to spores that might have been present on old residue, potentially leading to disease development and mycotoxin problems.
• Planting after soybeans or other legumes is the best solution. However, it's not risk-free. "The fungus can hang around in corn residues in soybean fields. If a soybean field is near corn fields, that fungus can blow in from neighboring fields," said Thomison.
• Switching to full conventional tillage might work, but only if the neighbors are practicing it too. "If you switch to conventional tillage and your neighbors are in no-till, that's not going to stop the fungus from moving from one field to the next," says Thomison. "It has to be practiced sort of on a 'global' scale, which is not feasible." Moreover, before growers take this step, Thomison said they should remember that the advantages of reduced tillage usually outweigh its disadvantages (especially with regard to soil and energy conservation).
• Select hybrids of different maturities and silking dates to promote genetic diversity and spread possible risk. "Nevertheless, you could still end up with a susceptible hybrid," says Thomison. "Because of their relatively rare occurrence, ear molds are normally not diseases that are evaluated in performance trials. But perhaps that will change, given the problems growers experienced last year."
While ear molds are usually not major concerns of most corn growers when it comes to diseases in Ohio, technology and crop management might be creating more opportunities for disease development.
"We are pushing plant populations. Last year, over 30% of Ohio's corn had final stands exceeding 30,000 plants per acre. That higher plant population is creating more residue in the fields," says Thomison. "Also, stalk quality has improved. It's doing wonders keeping corn upright and harvestable, but it's making those stalks tougher and that may slow residue breakdown."
That's why, said Thomison, breaking down the residue is so important.
"The fungus is ubiquitous. There's no way to completely get rid of the disease, but there are steps growers can take to minimize that risk," he says.