For corn that survives significant flooding, there could be a season of challenges ahead.
“Even if the ponding doesn’t kill plants outright, it may have a long-term negative impact on crop performance. Growers need to watch their fields closely for root and stalk rot, which can lead to lodging problems later in the season and could have negative impact on yields,” said Peter Thomison, Ohio State University Extension corn specialist. “The muddy, saturated fields have prevented producers from being able to spray and fertilize causing concerns over disease, growing pest presence, and increasing weed pressure. Fields washed out from prior rain events have yet to be replanted due to continued rain, and there is speculation it will be too late to replant. Yellowing of field crops and areas of sudden death are popping up around the state.”
Thomison said that moving forward, the success of flooded corn is dependent on three factors: what growth stage the crops were in at the time of the flooding event; how long the plants experienced ponding; and the air and soil temperatures during the event.
“Plants past the V6 growth stage should survive pretty well,” he said. “Prior to the 6-leaf collar stage, as measured by visible leaf collars, or when the growing point is at or below the soil surface, corn can usually survive only two to four days of flooded conditions.
“Plants prior to the V6 growth stage are more vulnerable to damage from ponding and saturated soil conditions. The oxygen supply in the soil is depleted after about 48 hours in flooded soil. Without oxygen, the plant cannot perform critical life-sustaining functions. If temperatures are warm during ponding — greater than 77 degrees F — plants may not survive 24 hours.”
Corn that does survive flooding might face a nitrogen deficiency later, Thomison said.
“Excess moisture during the early vegetative stages retards corn root development. As a result, plants may be subject to greater injury during a dry summer because root systems are not sufficiently developed to access available subsoil water,” he said. “Many Ohio fields are pockmarked with spots where the corn plants are stunted, which is exacerbated by the nitrogen-loss issue.”
Shaun Casteel, a Purdue University soybean specialist, said that although conditions for planting were marginal to begin with, the positive development is that there has been enough moisture to allow root systems to grow through compacted soil. Nitrogen loss has gone well beyond normal, though, so soybean plants may need “a shot in the arm” with additional nitrogen when conditions warrant
The wet conditions have set the stage for soybean diseases that could plague the surviving crops for weeks to come. OSU Extension plant pathologist Anne Dorrance pointed out the importance of scouting for foliar diseases to try and salvage profitability from flooded soybeans stands.
“Foliar pathogens have the most impact on soybeans at the later growth stages (R3 to R6) by reducing the photosynthetic area of the leaves that contribute to pod development and seed growth,” she said in a recent CORN Newsletter. “Soybeans also have an uncanny ability to compensate for missing neighbors. The profitability measure for the 2015 season will be to scout for the occurrence of diseases after flowering R3 and choose the best fungicide if necessary.”
Dorrance compiled a list of key diseases to scout for:
1. Septoria brown spot
This is a lower canopy disease, which surprisingly, we have not been getting too many reports of this year. Where we are, it is from fields that are planted into continuous soybean and have heavy residue. Even in these situations, the yield loss for this is still on average two to three bushels per acre.
2. Frogeye leaf spot
This disease we are monitoring, not only because there are a few highly susceptible varieties but also because there are reports from Illinois, Indiana, and up and down the Mississippi of populations that are no longer managed by the strobilurin class of fungicides. If you see it, please send this to the lab immediately, so we can run some tests. We have seen yield differences with low levels of disease (5% to 12% leaf area affected) of five to 10 bushels per acre. This is the one to keep an eye out for and the timing for sprays is between R3 and early R4.
3. Sclerotinia stem rot or white mold
For those fields with a long history of this disease, this can cause problems when we have cool nights (no air conditioning turned on in your house) and heavy dews. We have started our scouting for this pathogen as fields begin to get closer to flowering. However, for those historic areas where white mold is always present and a susceptible to moderately susceptible variety was planted, a fungicide may be necessary this year. The key is the timing, and coverage of the fungicide in the field. The target area is the lower part of the stem. Some cautions: we have not been able to reduce white mold with a fungicide nor with a herbicide if the field is planted to a highly susceptible variety and the crop is in full flower and infections have already occurred. These materials mainly work as protectants and have to be on the plant at those lower nodes to protect it prior to the arrival of the pathogen.
In terms of possible materials to use for controlling white mold Dorrance pointed out the following in a recent CORN Newsletter.
Approach: we have measured significant reductions in white mold when we applied this fungicide at Western branch right before flowering followed by a second application 10 days later.
Endura: we have measured significant reductions in white mold with this fungicide with one application timed at R1 when a few plants are beginning to flower in the field.
Phoenix and Cadet Herbicides: both have reduced the incidence of white mold in trials in northeast Ohio. If you are also going after weed escapes, this may also be a tool to consider.
Topsin M: this has been the standby white mold fungicide, but for the past three years, we have not been able to measure reductions in disease.
“For foliar pathogens there is time to let the plants recover and take a look later in the growing season to determine if the pathogens are present,” Dorrance said. “This is the year to focus those scouting efforts on highly susceptible varieties. For historic white mold areas, this will be another year to implement measures on those highly to moderately susceptible varieties.”
Just as it was approaching harvest in late June, the northwest Ohio wheat crop was pummeled by another round of heavy rains, creating quality and harvest delay concerns.
“Late harvest coupled with excessive rainfall mean more time for late-season mold growth, mycotoxin accumulation, test weight reduction, and sprouting, all of which collectively could result in poor overall grain quality,” wrote Pierce Paul and Laura Lindsey with OSU Extension in a recent CORN Newsletter.
Low test weights and resprouting can be significant problems if the mature grain is rewetted. Mold is another concern with wet weather and harvest delays.
“To fungi, mature wheat heads are nothing more than dead plant tissue ready to be colonized. Under warm, wet conditions, saprophytic fungi (and even fungi known to cause diseases such as wheat scab) readily colonize wheat heads, resulting in a dark moldy cast being formed over the heads and straw. This problem is particularly severe on lodged wheat,” they wrote. “In general, the growth of blackish saprophytic molds on the surface of the grain usually does not affect the grain. However, the growth of pathogens, usually whitish or pinkish mold, could result in low test weights and poor overall grain quality. In particular, in those fields with head scab, vomitoxin may build-up to higher levels in the grain, leading to further grain quality reduction and dockage. While vomitoxin contamination is generally higher in fields with high levels of wheat scab, it is not uncommon to find above two parts per million vomitoxin in late-harvested fields that have been exposed to excessive moisture. Even in the absence of visual scab symptoms, the fungi that produce vomitoxin may still colonize grain and produce toxins if harvest is delayed.”
To maintain quality, the wheat should be dried below 15% moisture before storage.
Of course the wet conditions in many parts of Ohio have made it very challenging for hay growers. While it can be extremely frustrating to watch hay quality deteriorate in the field, OSU Extension forage specialist Mark Sulc has been emphasizing the need for patience.
“They know that forage quality is declining with each day that goes by,” Sulc said. “However, I want to urge hay producers to change their focus and be patient, to make sure their hayfields are dry enough to support their equipment before they try to get out on them once the sun starts to shine again.
“The loss of quality in one cutting, even the complete loss of the value of one cutting, is less than ruining a forage stand for the remainder of its productive life by running equipment on ground that is still too soft, especially if it is a younger stand. So do what is really easy for me to say, but super hard to practice right now — just be patient. Take the long look and wait until the field is dry enough to support the equipment without damaging the forage stand.”
Sulc also said that these more overgrown fields of hay are much more tolerant to flooding damage than newly harvested hay fields.