Fields that looked green and healthy two weeks ago are taking on a pale look with brownish leaves ion spots right now. One factor, seedsmen say, is that since growing degree days are running so far ahead, the corn is simply reaching maturity.
That's one scenario. If the scenario is that disease or other problems cause the crop to die prematurely, how much will yield be affected? The answers, or at least a guide to the answers, may lie in the 2010 edition of the Purdue University Corn & Soybean field guide.
Based on apst research, tables inside the guide estimate how much yield loss you can expect if plants die prematurely at different stages.
If black layer ahs occurred, then the plant is finished. While yield may not be what you expected because the plant didn't produce and put more starch into the kernels near the end of the season, there shouldn't be any yield loss from pre-mature death of plants, per se. However if the milk line is only half-way down in the kernels, on average, and leaves die, the loss is estimated at 6%. So 200 bushels is 188 bushels per acre.
If the entire plant dies at that stage, past research says the yield loss is closer to 12%. So now that potential 200 bushels per acre becomes 176 bushels per acre. Grain moisture is typically 40% for plants killed at half-milk line stage. When plants reach black layer maturity on their own, the estimated moisture is around 32%.
It's when leaves and/or plants die earlier that severe losses develop. It's more typical to think of those situations in an early frost situation. But for whatever reason, if corn is full dent but the milk line hasn't dropped and the leaves die, you could back yields back by 27%. Now you're talking under 150 bushels per acre if the original potential was 200 bushels per acre. And in the worst case scenario, where the entire plant dies with corn at full dent, yield loss is estimated at 41%. Suddenly you're struggling to get 120 bushels per acre. Corn will also have a ways to dry down, starting at about 55% if leaves die with corn in full dent.
Bottom line is that corn isn't made until it's in the bin.