We are starting to see a few more tassels around the area. Once we see those tassels the plant will no longer grow up (with new leaves) or down (by increasing root mass). We have the entire structure built, now it will concentrate all resources into the ear and producing seed. The leaf at the ear is the critical leaf on the entire plant now. We protect it by watching for nutrient deficiency coming up from the bottom of the plant in nitrogen or potash, and we protect it from disease coming down from the top (usually). I saw a study showing yield loss when removing all the leaves above the ear, all the leaves below the ear, and removing just the ear leaf. The removal of just the ear leaf had the greatest yield loss. We are going to try this and we will let you know what we find.
Growth up and down will end soon, this also means we have all the root mass we are going to get. A dry soil should allow plenty of root penetration, however, roots need soil contact, air, and water. We saw this earlier in the season with some rootless corn due to lack of moisture. Our roots can only take up the nutrients immediately near the root. A lack of moisture means not only less root growth, but also, a lack of nutrients moving in the soil solution to be diffused into the plant. A few good rains would definitely help push the potential as we get into grain fill. The charts are not new, but from the U of IL showing we still have a lot of nutrient uptake to go, and it all goes toward grain once we reach R1.
Sunlight is critical now. As these plants prepare to pollinate and through pollination, we need the “factory” running at 100%. That means photosynthesis helping produce sugars within the plant to help regulate temperature, keep nutrients flowing, and kernels pollinating. Full, bright sunny days and moderate temps will help get all those kernels pollinated. We can’t change the number around (we are finding a lot of 16-18 and even some 20’s), and we can’t change potential length. BUT we still need to pollinate every silk. Any stresses during pollination will cause the plant to “tip-back” and about the end kernels. Our best yields come from filling those ears all the way out. Some hybrids genetically will form a nose or tip-back, but getting them 45 long instead of 34 long is the first big step coming up.
Corn diseases – We were able to find a few leaves today walking fields with the first stages of disease starting. What we saw were the first signs of rust, some eyespot, and what appears to be gray leaf spot. The free water in the form of dew every morning now is going to increase the chance for not only fungal diseases, but also bacterial diseases such as Goss’ Wilt and bacterial leaf blight. A fungicide will not protect from the bacterial diseases. The fungicide will help protect from northern corn leaf blight, gray leaf spot, eyespot, rust, and tarspot (we haven’t talked about the last one much yet). Last year pressure was low and we always try to compare to the last year, but each year will be different. Looking back at notes, we’ve had seasons with no signs of any disease near tassel time and then the pattern changes, we get spores blowing in from the south and heavy dew in the morning and disease can advance quickly. Don’t start to cut back now, our last chance to put the top end on this crop is coming up soon. We are still taking names for the fungicide application list – we still have plenty of product. Veltyma seems to be the most common choice. Give us a call with any questions and how we can help you reach the top end yet.
Another point to consider – different hybrids have different responses as we’ve shown before. Some products need more protection during that pollination phase because they will abort the end kernels easier. Others need protection later because their yield comes from kernel depth. Timing your application to protect that plant as long as possible in the absence of current stress usually pays the best.