Crop Updates: Weed control has been a challenge in these hail-damaged fields. If needing a harvest aid for corn, 2,4-D or Aim can be used after beginning dent. Glyphosate and Gramoxone can’t be used till black layer. All need to be applied at least 7 days prior to corn harvest. For soybean, don’t go too early. Sharpen is the most commonly used with a 3 day pre-harvest interval and we say to apply at the combination of these things: 65% of pods are brown, there’s more than 70% leaf drop, and seed moisture is less than 30%.
For a few weeks many have observed corn plants rapidly dying in the area, both in irrigated and non-irrigated fields. There has been some Goss’s wilt (leaf version) out there, but I’ve seen more instances of dying leaves being called Goss’s when it’s not. And, that’s an important diagnosis as you think about hybrids for the future. For Goss, look for a shiny, almost varnished appearance on the lesions. In the very edges where the lesion is more ‘water-soaked’ and light-green in color, you should often see the presence of black specks that look like pepper. Some lesions being confused with Goss’ are actually northern corn leaf blight, but it doesn’t have a shiny varnished appearance and will have cigar-shaped lesions usually between the midrib and leaf edge. These lesions can eventually blight entire leaves and may be what’s occurring in some hybrids.
I have seen some anthracnose top die-back in some fields (look for top leaves flagging bright yellow and senescing from top towards middle of plant). I’ve also seen a lot of crown rot in fields…since early this growing season. At that time, it wasn’t something we considered for replant because it doesn’t usually kill plants then. It does hinder water and nutrient uptake at this point in the season, and I think that’s the greater issue combined with higher soil temperatures (up to 8F higher than normal) and water stress. There’s nothing we can do about any of these problems, but you can take note of hybrid differences right now. If you want to see if crown rot is playing a role, dig up a plant with leaves that are rapidly dying and slice the stalk open. For crown rot, you will notice a browning in the crown area and sometimes even up higher on the internodes. Fields that received hail damage and weren’t replanted are also showing greater rot into the stalks where you can see the original hail stone damage that penetrated.
Irrigation: I know you’re weary of irrigating. The blessing of this slow fill period is packing on weight with deeper kernels. We’ve known for some time that we will most likely be irrigating replant crops while harvesting. Some need this replant crop to fill contracts while others are trying to get by without many additional inputs. For several weeks I’ve thought about ‘how much yield do we give up if we stop irrigating at X’. Was thinking about this for those who get tired and are ready to shut off early and for the replant corn if shutting off early can move it along/get it to dry down faster. Wasn’t sure how relevant this thinking was till two farmers asked me. So, the following is combined from ISU’s ‘How a Corn Plant Develops’, ‘Last irrigation of the season’ NebGuide, and info. from some plant breeders if it can be helpful for your decision making going forward. The caveat is that hybrids differ, thus the range, so perhaps also talk with your seed dealer. For corn:
- Beginning dent needs 5.0” water, around 24 days to maturity, 25-55% yield loss potential.
- ¼ milk needs 3.75” water, about 19 days to maturity, 15-35% yield loss potential.
- ½ milk needs 2.25” water, about 13 days to maturity, 5-10% yield loss potential.
- ¾ milk needs 1.0” water, about 7 days to maturity, around 3% yield loss potential.
I don’t have the same numbers for soybean, but in much of the soybean replant, I’m seeing beans that either caught up to the old stand development stage or are up to 3 stages behind it. The biggest thing I’ve seen in replant soybean in the past is having beans at a variety of development stages at harvest…from lima beans to dry bbs, particularly when later maturity groups were planted as replant compared to the original maturity group. Regarding all who ask me if this replant corn crop will make it, for now, let’s just leave it that I genuinely hope and pray it does! Each day is one more day closer!
Crown Rot: Was seeing this early on in the growing season in the below-ground nodes (left triangle area) and seeing quite a bit now as well (right). Regardless of the specific pathogen causing this, what we observe this time of year is leaves rapidly dying and rotted crowns on plants such as what you see in the plant on the right. This plant is actually rotted to the vascular bundles in the crown area with rot progressing up the plant into subsequent internodes and nodes.