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Making corn fungicide decisions

The 2011 crop season got off to a slow start for many farmers, and with delayed planting came concerns about reduced yields. Growers are encouraged to protect yield potential by taking advantage of every opportunity to produce the highest-quality grain and crops. One way to achieve a greater profit is by improving the standability of corn plants and preventing lodging at harvest.

Losing corn due to poor standability is frustrating. It can be a nightmare getting a combine through broken stalks and lodged plants. While stalk damage from strong wind and hail is sometimes unavoidable, there are ways to ensure stronger stalks to withstand severe weather.

“Standability is important so the corn stands as long as possible until you can get in to harvest it,” says Alison Robertson, an Iowa State University Extension plant pathologist. “If you don’t have good standability, and you get a strong wind or a strong storm coming through, that’ll knock a lot of corn to the ground. You have to reduce your harvesting speed so you can get in and pick up as much of the corn that’s lying on the ground as possible.”

Key Points

Improving corn standability, harvestability is a goal growers strive to achieve.

Leaf diseases contribute to stalk rot issues; managing diseases is important.

Ask the seed company if it thinks a hybrid should be treated with foliar fungicide.


In addition to reducing harvest efficiency, harvesting lodged corn with a combine can prove to be a fruitless task. “When corn lodges, oftentimes the ears are in close contact with the ground and that can lead to ear rot,” says Robertson. “If the growers even manage to get the ears off the ground with the combine, they still may have a problem with poor-quality grain because of the ear rot developing in that downed corn.”

The potential yield loss from decreased standability can put a strain on both a grower’s combine and wallet. Annual yield losses due to stalk lodging in the U.S. are estimated between 5% and 25%. In addition to outright yield losses, grain quality may also decline as a result of stalk lodging.

The remaining lodged corn may also provide seed for the following year’s volunteer corn in rotated fields. But all hope is not lost. Instead of leaving the harvestability of the corn crop to chance, Robertson has some recommendations about getting the most from what is planted.

Manage corn leaf diseases

“Growers should talk with their seed dealer and try and get hybrids that have better standability scores,” says Robertson. “The other thing we know is there’s a very strong relationship between leaf diseases and stalk rots, and therefore decreased standability, so managing leaf diseases in the field is also important.”

Research shows strobilurin fungicides offer disease control and physiological benefits, such as stronger stalks and improved standability leading to an easier harvest. Strobilurin fungicides are designed to provide corn with effective control against a wide array of yield-robbing diseases that can cause stalk rot and decreased stands.

“We’ve seen excellent field performance from strobilurin fungicides, such as Quilt Xcel,” says Eric Tedford, fungicide technical brand manager for Syngenta.

“We’ve researched the physiological benefits of strobilurin fungicides since their development in 1992, and results have shown the enhanced plant performance produces thicker, stronger stalks, less lodging and greater harvest efficiencies. This translates into greater return on investment.”

Should you apply fungicide?

Should you apply a foliar fungicide on your corn? Or should you apply a fungicide on some acres and not others?

Purists who go strictly by the rules of Integrated Pest Management will tell you to only spray if signs of disease warrant it. Those on the other end of the spectrum look at using a fungicide as a type of insurance, especially in corn-after-corn fields, and may spray every acre whether they see a disease lesion or not.

If you sprayed this year, how do you know if you are getting a return on your investment? How will you make the spray-or-not-spray decision next year?

One way to help you make that decision is to consult with your seed representative. Most companies are finding out whether it pays or not is typically a hybrid-by-hybrid answer. The seed company, which knows the genetics, can tell you if they think a hybrid should be treated with a foliar fungicide. For example, Golden Harvest has a two-page summary of all its hybrids, and makes it clear which are likely to see a response and which aren’t if little disease is present. With disease present, an application is more likely to pay on any hybrid.

Consult your seed sales rep

The table in Syngenta’s summary shows what happened when Quilt Xcel fungicide was applied. Hybrids were divided into four classes. For the two classes where Golden Harvest plant breeders expected a response, there was a response in 83% and 80% of all comparisons, respectively. The application produced an economic return 77% and 60% of the time, respectively.

But for the two categories where breeders predicted a response was less likely under low to moderate disease levels, the yield response was 74% and 52% of the time, respectively, but there was economic payback only 43% and 17%. If you were planting the hybrid that responded 83% vs. 42% of the time, wouldn’t you want to know? Your seed representative may have similar information for the hybrids he or she sells.

This article published in the August, 2011 edition of WALLACES FARMER.

All rights reserved. Copyright Farm Progress Cos. 2011.