Time to Get Serious About Scouting for Disease

You should know where disease could become an issue.

Published on: Jul 6, 2009

Two years ago this week, we sprayed demonstration strips in the high-yield plots of the Corn Illustrated project on the Facemire Farms near Edinburgh, Ind. While we're no longer doing those plots, lessons learned there still apply today.

 

There wasn't a lot of disease present that year at the time, notes Dave Nanda, who served as consultant for the plots. Nanda is currently president of Bird Hybrids, Tiffin, Ohio. However, since the idea was to see what might produce top yield, we agreed to spray strips anyway. The application was made over the top with ground equipment. Pollination was complete or nearly complete. That season was the hot, dry one - timing ran ahead of schedule. The field where the fungicide was applied was irrigated.

 

At harvest, the yield boost wasn't huge, but it was enough to pay for the application and then some, Nanda recalls. So the following year, in 2008, we decided to include it as part of the regimen for the high yield plot where we were shooting for 300 bushels per acre. Unfortunately, we didn't leave test strips last year. Although there was again little sign of disease when the application was made, this time there appeared to be some minor damage on many ears. The smoking gun pointed to the fungicide application, although ti was never conclusively proven. What was discovered was that the application was made before pollination was complete.

 

Nanda and the person advising the applicator mis-communicated. The difference between tasseling and pollination being complete got lost in the interpretation process, and could explain why there was minimal damage, Nanda notes. The corn still made 200 bushels per acre, planted in late May, under irrigation, on average soils at best. However, the year before, a much hotter summer, but planed in early May, the top yield reached 245 bushels per acre.

 

What all this means for this year is that now is the time to scout fields. You ay already be on a list to have fungicide applied. But if there are no disease symptoms showing on leaves in the field when it's time for the application, Nanda believes it likely won't pay to apply the fungicide. A check of head high corn in southern Indiana just days ago showed virtually no signs of leaf disease, even after a week of hot, humid weather.

 

Various pathogens like different conditions. Some like it cool and dry, other hot and muggy. The variety is certainly there so far this year. Whether Mother Nature is doling it out in doses long enough to get infestations started remains to be seen.

 

Just noting one field isn't a bell weather for the entire state, either, by any means. Some hybrids are naturally resistant to many leaf diseases. Others are more susceptible. It's the susceptible ones where fungicides are likely to pay the biggest return, Nanda says. The only way to know the best course of action is to know the characteristics of the hybrids you have planted in each field, and then to scout those fields where corn could be susceptible often and without fail. As disease symptoms become more prevalent on leaves and especially on leaves closer to the ear leaf, it should be easier to justify a fungicide treatment.