C.O.R.N. Newsletter: 2016-13
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PLANT PLANT PLANT!!!
The weather pattern has become favorable for planting. In the short-term planting is favorable but it could become less favorable in the next 1-2 week again so it is worth taking advantage of the window.As expected our weather pattern has changed to a much warmer one. This will persist for some time now. Temperatures for the rest of May will average +5F. This will allow May to go down as 0 to -1F for the month and it looks like the period of March to May will actually go down as +1 to +2F even with recent coolness.
Drying conditions will be excellent until Wedneday as relative humidity will be quite low until midweek. Humid conditions with dewpoints in the 60s will return Wednesday into the holiday weekend.
There will be a shift of the main rain focus to the western half of the corn and soybean belt over the next 2 weeks. Rainfall in the eastern sections will be close to normal. Normal is about an inch per week. Due to scattered thunderstorms starting Wednesday and on, rainfall will be quite variable. Rainfall through the rest of May will average 0.75 to 1.00 but will range from 0.25 to 2.00 inches. This is common in summer-time type patterns.
The outlook for June calls for temperatures +1 to +2F with rainfall 0 to +1 inches.
The outlook for July calls for temperatures 0 to +2F with rainfall -1 inch.
Outlook period Temperatures RainfallRest of May +5F 0.25-2.00 (averaged 0.75-1.00) inchesJune +1F to +2F 0 to +1 inchJuly 0 to +2F -1 inch -
Adjustments for Late Planted (or Replanted) Soybean
Wet weather has kept many farmers (and us) out of the field. According to the USDA National Agricultural Statistics Service, as of May 15, 10% of the soybean acres were planted. At the same time last year, 46% of soybean planting was complete. On average, in Ohio, the majority of soybean acres are planted mid to late May (Table 1). Although, it is not uncommon for soybean planting to creep into June. In general, we don’t recommend altering soybean management until planting in June. Below are some guidelines to consider if planting soybeans in June.
Row spacing. Regardless of planting date, we recommend planting soybean in narrow rows (7.5 to 15 inches). The goal is to have row widths narrow enough for soybean canopy closure by the time flowering occurs in late June/early July. This becomes even more important as soybean planting is delayed. The later in the growing season soybeans are planted, the greater the yield increase due to narrow rows.
Seeding rate. If planting soybean during the first half of June, a seeding rate of 200,000 to 225,000 seeds/acre is recommended. At a seeding rate of 200,000-225,000 seeds/acre, the final stand should be adequate to maximize yield (see Figure).
Relative maturity. Relative maturity has little effect on yield when planting during the first three weeks of May. During the first half of June, a four-day delay in planting delays physiological maturity about one day. As planting is delayed, yield potential goes down, and there is concern about whether late maturing varieties will mature before frost. When planting late, the rule of thumb is to plant the latest-maturing variety that will reach physiological maturity before the first killing frost. The reason for using late-maturing varieties for late planting is to allow the plants to grow vegetatively as long as possible to produce nodes where pods can form before vegetative growth is slowed due to flowering and pod formation. Table 5-4 from the Ohio Agronomy Guide gives the recommended soybean relative maturities for June and July planting dates. With these recommended relative maturities, soybeans should not get damaged by frost occurring at the normal time.
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Corn Replant Tips
Although most corn that’s been planted has yet to emerge or develop much beyond the VE or V1 stage, there are localized reports of growers replanting early planted corn. Some of these replant issues appear related to the consequence of recent frost injury combined with excess soil moisture or flooding.
Replant decisions in corn should be based on strong evidence that the returns to replanting will not only cover replant costs but also net enough to make it worth the effort. Don’t make a final assessment on the extent of damage and stand loss too quickly. The following are some guidelines to consider when making a replant decision.
If the crop damage assessment indicates that a replant decision is called for, some specific information will be needed, including:
Original target plant population/Intended plant stand
Plant stand after damage
Uniformity of plant stand after damage
Original planting date
Possible replanting date
Likely replanting pest control and seed costs
To estimate after‑damage plant population per acre, count the number of viable plants in a length of row that equals 1/1000 of an acre and multiply by 1000. Make several counts in different rows in different parts of the field. Six to eight counts per 20 acres should be sufficient. Table 1 below shows row lengths required to equal 1/1000 acre when corn is planted at various row widths.
Table 1. Length of row required for 1/1000 acre at various row widths1
Row width (in.) Length of row for 1/1000 A
15 34 ft., 8 in.
20 26 ft., 2 in.
28 18 ft., 8 in.
30 17 ft., 5 in.
36 14 ft., 6 in.
38 13 ft., 9 in.
40 13 ft., 1 in.
42 12 ft., 5 in.
1Example: For 30” rows, count the number of kernels dropped or the number of plants in 17 ft., 5 in. and multiply by 1000. If there are 21 in the 17 ft., 5 in. row, the population is 21,000 per acre.
A major consideration in making a replant decision is the potential yield at the new planting date and possibly different planting rate; this can vary depending on the hybrid used, soil fertility and moisture availability. Table 2 is adapted from a chart developed by Dr. Emerson Nafziger at the University of Illinois that shows effects of planting date and plant population on final grain yield for the central Corn Belt. Dr. Bob Nielsen at Purdue University modified this table to provide estimates of potential yield losses for planting dates in early June (on-line at http://www.agry.purdue.edu/ext/corn/news/articles.08/delayedpltupdate-0523.html)
Grain yields for varying dates and populations in both tables are expressed as a percentage of the yield obtained at the optimum planting date and population.
Here’s how these Table 2 might be used to arrive at a replant decision. Let’s assume that a farmer planted on May 9 at a seeding rate sufficient to attain a harvest population of 30,000 plants per acre. The farmer determined on May 28 that his stand was reduced to 15,000 plants per acre as a result of saturated soil conditions and ponding. According to Table 2, the expected yield for the existing stand would be 79% of the optimum. If the corn crop was planted the next day on May 29 and produced a full stand of 30,000 plants per acre, the expected yield would be 81% of the optimum. The difference expected from replanting is 81 minus 79, or 2 percentage points. At a yield level of 175 bushels per acre, this increase would amount to a gain of about 3.5 bu per acre.
It’s also important to note plant distribution within the row. Remember that values in replant charts like Table 2 are based on a uniform distribution of plants within the row. Add a 5% yield loss penalty if the field assessment reveals several gaps of 4‑6 feet within rows and a 2% penalty for gaps of 1‑3 feet. Yield loss due to stand reduction results not only from the outright loss of plants but also from an uneven distribution of the remaining ones. The more numerous and longer the gaps between plants within the row, the greater the yield reduction. It’s also important to consider the condition of the existing corn.
When making the replant decision, seed and pest control costs must not be overlooked. Depending on the seed company and the cause of stand loss, expense for seed can range from none to full cost. As for the correct hybrid maturity to use in a late planting situation, continue to use adapted hybrids switching to early/mid maturities, if necessary, depending on your location in Ohio.
You also need to review herbicide and insecticide programs under late‑planting conditions. For instance, it may be necessary to reapply herbicides, especially if deep tillage is used. However, try to avoid such tillage depending instead on postemergence chemicals or cultivation for weed control. Concerning insect control, if soil insecticides were applied in the row at initial planting, check insecticide label restrictions before re‑application. Also remember that later May and June planting dates generally increase the possibility of damage from European corn borer (ECB) so planting ECB Bt hybrids is often beneficial.
The cost of replanting will differ depending on the need for tillage and chemical application. The cost and availability of acceptable seed will also be considerations. These factors must be weighed against expected replanting yield gains. If after considering all the factors, there is still doubt as to whether or not a field should be replanted, you will perhaps be correct more often if the field is left as is.
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Time to Scout for Black Cutworm in Corn
We have started to see cutworm damage in Ohio corn. Black cutworm (BCW) is the prime offender, though other species exist. Adult BCW (moths) are migrants from the south that start moving into Ohio in April, and lay eggs that hatch into the cutworm caterpillars. Although there are some hotspots for egg laying, these predictions are far from exact. Moths tend to seek out fields with a lot of weeds, especially winter annuals such as chickweed, to lay their eggs. The eggs are laid in the weeds and the tiny larvae feed on the weeds until the weeds are killed by herbicide or tillage at which time the larvae will move onto the corn planted in the fields. An additional concern related to corn is that most of the crop is being planted relatively late this spring. Corn will be rather small when larvae of these pests begin their heavier feeding. Thus, the potential for plant injury and subsequent economic losses will be much higher than normal because of the size of the corn. Black cutworms go through seven instars, with only the last four producing the greatest amount of injury.
Insecticidal seed treatments do not offer much protection. Some Bt corn train packages provide BCW protection and some do not (http://msuent.com/assets/pdf/28BtTraitTable2016.pdf). Early detection of cutworm infestations and timely application of rescue treatments are the keys to
achieving effective stand protection. Start scouting for BCW as soon as the corn begins emerge. Rescue treatments can then be applied if necessary. If cutting is above ground, cut plants will likely recover if a timely rescue treatment is applied. In contrast, below ground feeding is generally characterized by by wilting plants that have been cut below the growing point, or plants cut off before emergence, and is harder to recover from. Soil moisture conditions can sometimes dictate where you might expect to find cutting with above ground cutting occurring under moist soil conditions and below ground cutting occurring under dry soil conditions. Treatment is warranted when visible cutworm injury is observed on 3% to 5% or more of a stand. If a significant cutworm infestation is detected too late, cutting has occurred below ground and below the growing point, then a rescue treatment may achieve only marginal results.More information about cutworm biology, scouting, and management can be found at http://ohioline.osu.edu/factsheet/ENT-35
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Impact of Frost on Soybean and Corn Survival
Soybean: Last Monday, May 16, air temperatures dropped to high 20s/low 30s causing some freeze injury to soybeans. Soybeans in low areas of the field are most likely to be affected. Plants should be assessed for damage at least five days after suspected injury to inspect for regrowth. If damage occurred above the cotyledons, the plant will likely recover. If damaged occurred below the cotyledons, the plant will not recover. Look for a discolored hypocotyl (the “crook” of the soybean that first emerges from the ground) which indicates that damage occurred below the cotyledons. The soybean plant pictured will not recover. If soybeans were not yet emerged at the time of the freeze, they should be fine.
If widespread freeze damage occurred, it is not too late to re-plant (see the Late-Planted Soybean article in this issue of the CORN newsletter).
Corn
Although early planted corn has been severely damaged by recent frosts in some areas, the effects of the low temperatures on corn survival will probably be
negligible for the most part. In past years, we have observed that corn that was in the process of germinating or as far along as the V1 stage (one leaf collar visible) survived freezing soil temperatures in April with little impact on crop performance or plant stand. Agronomists generally downplay the impact of low temperature injury in corn because the growing point is at or below the soil surface until V6 (six leaf collars visible), and thereby relatively safe from freezing air temperatures. Moreover, the cell contents of corn plants can sometimes act as an "antifreeze" to allow temperatures to drop below 32 degrees F before tissue freezes, but injury to corn is often fatal when temperatures drop to 28 degrees F or lower for even a few minutes.
Effects of low temperatures on germination are far more serious when combined with snow and freezing rain. When dry corn seed absorbs cold water as a result of a cold rain or melting snow, “imbibitional chilling injury” may result. However these conditions were largely absent following the recent frosts.Several studies have indicated that cool conditions following frost could lead to continued plant mortality as a result of bacterial stalk rot diseases. In Ohio, we’ve observed extensive stand loss in early corn subjected to heavy rains shortly after hail damage and defoliation. The increased plant mortality was associated with what appeared to be bacterial soft rot.
To assess the impact of freezing temperatures on emerged corn, check plants about 5 days after the freezing injury occurred (and preferably when growing conditions conducive for regrowth have occurred). New leaf tissue should be emerging from the whorl. You can also observe the condition of the growing point (usually located ½ in to 3/4 in below the soil surface) by splitting seedlings lengthwise. If the growing point appears white to light yellow and firm several days after the frost, prognosis for recovery is good.
For more information on frost effects on early planted corn, check out the following:
McMechan, J. and R. Elmore. 2016. Risk of Freeze Damage in Early Planted Corn. Cropwatch. University of Nebraska – Lincoln. http://cropwatch.unl.edu/2016/risk-freeze-damage-early-planted-corn (verified May 20, 2016)
Nielsen, RL (Bob). 2001. Symptoms of Low Temperature Injury to Corn and Soybean. Corny News Network, Purdue Univ. online at http://www.kingcorn.org/news/articles.01/Frost_Corn_Soy-0418_Gallery.html (verified May 20, 2016)
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Cressleaf Groundsel in Wheat and Hay
It’s definitely a big year for cressleaf groundsel (Senecio glabellus), that yellow-flowered weed that can be seen about everywhere right now. While it is most often found in no-till corn and soybean fields that have not yet been treated with burndown herbicides, there seems to be an above-average number of wheat and hayfields and pastures with substantial populations. Cressleaf groundsel can be identified by its hollow and grooved stem with a purplish color, and yellow sunflower-type flowers. It is a winter annual that emerges in late summer into fall, and can infest late-summer seedings of forages and hay, and fall seedings of wheat. It can be controlled with herbicides in most crops, ideally in the fall or early spring when plants are small and most susceptible to herbicides.
At this time of the year, plants are flowering and going to seed, thus ending their life cycle. Applying herbicides to hay fields at this time probably won’t do much to reduce the risk of toxicity to animals (and it’s too late to apply any herbicides to wheat). Plants that have flowered are more difficult to control, and will still be there even if killed by herbicides. Major management goals at this time are mowing infestations soon enough to prevent seed production, and deciding what the risk of toxicity in hay or straw is based on the level of infestation. Cressleaf groundsel should not be present in hay fields following the first cutting. However, it is advisable to scout fields in late fall for the presence of newly emerged plants, and treat with herbicides if necessary.
Cressleaf groundsel is poisonous to cattle, horses, goats, sheep, and humans due to the presence of pyrrolizidine alkaloids (PAs). Symptoms include weight loss, unthriftiness, poor hair coat, anorexia, behavioral changes, sunscald, aimless walking, diarrhea, jaundice, liver damage, and possibly death. All parts of the plant are toxic. Drying or ensiling the plants during the hay or straw making process does not reduce the toxicity of cressleaf groundsel. Historically, no confirmed cases of poisoning by S. glabellus have been reported by the Ohio Department of Agriculture’s Animal Disease Diagnostic Laboratory, although liver lesions suggestive of PA poisoning have been observed on rare occasions. Although the presence of the occasional plant in a hay or wheat field is probably not cause for concern, producers are advised to avoid harvesting areas of the field that have high concentrations of the plants. Or bale and discard hay or straw from those areas of the field, if this is more desirable than leaving the plant residue in the field.
This is not a new problem, and we have a fact sheet available on cressleaf groundsel at the OSU Weed Management website – http://u.osu.edu/osuweeds. Hover over “weeds”, and then click on “other” to get to it.
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Wheat Scab Update: Late-May 2016
Wheat is now flowering in parts of central Ohio and will continue to flower in more northern counties later this week and into next week. According to the FHB forecasting system (http://www.wheatscab.psu.edu/), the risk for scab is low in central and northern Ohio for fields flowering at this time (May 23). Although it has rained fairly consistently over the last 7-14 days, conditions were relatively cool last week, which likely reduced the risk of the scab fungus infecting the wheat spikes. Scab develops best under moderate to warm temperatures and humid conditions. Continue to keep your eyes on the weather and the forecasting system over the next week or so as there is rain in the forecast and warmer temperatures for later this week. Fields flowering at the end of this week or early next week (May 25-30) may still be at risk for scab. Prosaro and Caramba are the two fungicides recommended for head scab control. Stay away from the strobilurins when the risk for scab is high as they have been linked to higher grain contamination with vomitoxin. Click on the links below to see updated factsheet # PLPATH-CER-06 for more on head scab of wheat and barley and factsheet # PLPATH-CER-03 for guidelines on how to use and interpret the scab forecasting system.
Crop Observation and Recommendation Network
C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.
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