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NW Illinois | First field I was asked to look at 3rd week of August had exactly this. Affected field, Channel on bean stubble, drone applied Veltyma around brown silk. Then 2 feet of brome, woven wire fence, 2 more feet of brome. Neighbors field planted 2 weeks later, Dekalb, corn on corn, no fungicide (field too small with many obstacles for aerial app). Treated field 50% green tissue loss, Tar Spot top to bottom. Neighbors had maybe 5% the volume of spots of Channel field, but no tissue loss surrounding the spot at that point.
Second anomaly I'm trying to understand. I spray 6000 acres or so of high gallon nitrogen pre emerge every year. This is 175-195 units of N on bean stubble, 230 or so on corn on corn. Most all will have between 5 and 8 gpa of Thiosul. I spray with a Terragator with a double fence row nozzle design. Essentially it has 4 full flowing nozzles on the outer 8 feet or so. This was designed to help reduce the staggered corn height, in first couple rows, we saw on non fall AA applied fields, when the boom doesn't get enough to the field outer edges. So this is north of 300 units of UAN and north of 30 lbs of Sulfur. These plants are show 1/10th the damage from Tar Spot, as the plants 3 rows in or more. Same pattern as where I roll out of field corners spraying heavy, till I get up to speed. Toughest part of field to get fungicide to, but grass green.
Obviously I'm not suggesting everyone delay planting or spending a bunch of money over applying nitrogen and sulfur, but there is something other than the effects of fungicides at work going on here. I have researched online and haven't come up with anything really to help explain this.
As I said in another thread, I know nothing of Southern Rust, it's Tar Spot here. But every type of aerial application used this year didn't treat or suppress any noticeable pressure below roughly the ear. Not sure multiple apps is going to change anything there, unless you start when physical canopy is smaller to get lower penetration. May improve on the crappy coverage issues we have if they fly a different pattern or start on the other side of the field or something. | |
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Some real world fungicide results with pictures
