The first question to ask someone who says that fungicides boosted their yields in corn or soybeans is whether or not they left a check strip that didn't get a fungicide application. That's the first question Dave Nanda asks when someone wants to give him a report on how fungicides performed this year.
It was a hot, fast-paced year with lots of humidity, and certain diseases flourished. At the top of the list are gray leaf spot and northern corn leaf blight. First thought to be limited more to northern Indiana, northern corn leaf blight has been reported as a major thorn in the side of farmers much farther south within the state.
Still, if you don't have a check strip, you don't know for sure whether the fungicide helped, and if so, how much it helped, says Nanda, a crops consultant, and newly named director of research for Seed Consultants, Washington Court House, Ohio. The problem is that if you're using aerial applicators, it's very tough to leave check strips.
Nanda has worked with farmers who used ground equipment to apply fungicide. At harvest he noted that there was disease on the lower leaves, but it did not progress to the top leaves above the ear. The fungicide applied did its job. In cases with check strips, differences of 20 bushels per acre have been recorded.
The second part of the equation is whether the hybrid is susceptible to these leaf diseases he says. Most of his observations have come on popular hybrids in the industry that are susceptible to one or more leaf diseases.
The other factor is ground vs. aerial application. In most ground application instances, applicators apply up to 20 gallons per acre of volume to get good coverage. The typical aerial application rate is 3 gallons per acre. Weather that plays into results is not proven by data as far as anyone knows.
Preparing for next year, play more attention to which hybrids are susceptible and which are not, Nanda says. Also, if you're going with corn after corn, expect a higher risk of diseases pressure. If a high-yielding hybrid is susceptible but you want to plant it anyway, then be prepared.
However, that doesn't mean it's a lock you should spray, at least not in his mind, Nanda notes. The third leg of the stool is the right conditions for the diseases. If conditions are not favorable next year, and they were not favorable for the most part in 2009, then you may not need to spray, even if the hybrid is susceptible. Nanda successfully advised a farmer with a very susceptible hybrid in 2009 to wait to see what the disease did after they saw lesions in waist high corn. The weather changed and the lesions did not progress. The farmer did not spray. Yields were good, although he did not have a check strip.