Corn harvest is underway in Iowa. There are a lot of reports from farmers that yields of corn and soybeans are better than anticipated. Does that mean the crop is turning out better than earlier thought or are farmers harvesting the good fields first?
"It depends on what you anticipated for yields," notes Roger Elmore, Iowa State University Extension corn agronomist. "With such a hot July we were very concerned about poor pollination. Then the high temperatures speeded up crop development to where it was pushing development during those growth stages faster than we would have liked. But it probably could have been worse."
What is Elmore hearing now at harvest regarding corn yields around the state? "Some farmers are harvesting badly lodged corn, the fields that were blown down from the strong winds and they're getting quite a bit less yield than they would have had if the corn had not gone down. But other than that, I'm hearing yields across the board from lower than expected to higher than expected."
Tremendous yield variation across Iowa in corn and beans
There is a wide variation in yields across Iowa on corn as well as soybeans this fall. "We're hearing a lot of good reports and some disappointing yields as well," says Elmore. Southeast Iowa, for example, pretty much had a drought year in 2011. Actually, all of Iowa experienced some very dry weather this growing season, notes Elmore, and southeast Iowa suffered the most from lack of rain.
There are a lot of regional differences this year in both corn and soybean yields. Northwest will likely look better than southeast Iowa when the final yield results are tallied up for the crop reporting districts. It depends where you are and what kind of growing season weather you had.
Is there anything farmers should take away from their 2011 corn growing experience? What can farmers learn from this year and do differently for next year that will help them?
What did you learn from 2011 corn growing experience?
"There are always things to learn, I'm always on the learning curve," says Elmore. "We need to keep thinking, comparing and learning year-to-year. This year with the extremely high heat in July, I'm not sure we could have avoided a yield reduction, even with good hybrid selection.
You should plant a diverse selection of corn hybrids so your crop silks at different times, so fields aren't silking at the same time, he advises. That way you can avoid the consequences of a week or several days perhaps of stress occurring during the pollination period.
"But when we have three or four weeks of extremely hot weather like we did in July this year, there's not much you can do to avoid that," says Elmore. "I would always plant a diversity of corn hybrids, in order to spread out the silking dates and maturity dates."
Should you select hybrids for Goss's wilt resistance?
Another thing many Iowa farmers saw in 2011 is Goss's wilt, a foliar disease, which hammered some fields pretty hard and it was fairly hybrid-specific. You need to pay attention to corn hybrid selection for next year if you had a problem with this disease this year, says Elmore. Hybrids vary in their resistance to Goss's wilt.
Is Goss's Wilt a disease Iowa farmers can anticipate having a problem with next year? As mentioned, it is hybrid specific to a certain degree. That is, some hybrids have a higher degree of resistance to Goss's Wilt than other hybrids. Iowa farmers saw a little bit of Goss's Wilt in Iowa last year and more this year. Can they expect the same next year?
Elmore thinks Iowa farmers should expect that, based on what Alison Robertson, ISU Extension plant pathologist, has observed. "The pathogen that causes Goss's wilt survives in crop residue and it is also borne by the air, which means wind can spread it from field-to-field. If you had this disease in 2011 and you plant a susceptible hybrid in 2012, you are likely to have Goss's wilt again. So it's a consideration, especially for continuous corn."
What caused corn rootworm control failures in fields?
There were reports in northeast Iowa in 2011 that corn rootworm control was a problem in some corn hybrids, even Bt hybrids that contain the trait that supposedly makes the corn resistant to rootworm.
"There are always incidents of corn lodging and poor rootworm control that we hear about every year," says Elmore. "It depends on the pressure of the rootworm population, which can vary from area to area and field to field each year. Sometimes the transgenic gene in the corn plant fails to express itself. Other times the rootworm pressure is overwhelming. Shallow rooting of corn plants is another factor that can make a difference—especially in a wet spring like we experienced in 2011. So it could be a combination of factors that causes corn to lodge and poor rootworm control to result."
Combination of factors can cause poor rootworm control
Early in the 2011 growing season most of Iowa had pretty good soil moisture and rainfall, and as a result corn roots were fairly shallow this year. Then strong wind storms struck various areas later on at different times in the growing season. That also caused the corn plants which had shallower than normal root systems to lodge more easily.
"It may be rootworms, it may be shallow roots and it may be poor rooting characteristics of specific corn hybrids, or a failure of a genetic event to provide control, or a combination of all these factors, that caused corn to lodge this year," sums up Elmore.
Some farmers are reporting positive response to foliar fungicide
More farmers tried a foliar fungicide application on their corn this year. They applied one, and in some cases two, applications of fungicide on corn during the growing season. Some farmers say the fungicide increased their yields. Is that something you can expect year-in-and-year-out, or is corn response to fungicide going to be weather-specific?
"Not only weather specific, but it takes the disease pathogen to be there to get a positive yield response from fungicide application," says Elmore. "With weather conditions that favor development of the disease and the pathogen being there in the field, you could expect to get some degree of control with the foliar fungicide if it is applied at the right time."
Of course, it has to be a fungal disease that is present, says Elmore. Goss's wilt, for example, is caused by a bacteria, so there's no way a foliar fungicide will control Goss's wilt.