C.O.R.N. Newsletter: 2014-10
Temperatures are Still CoolAuthor(s): Anne Dorrance
Soil temperatures from around the state are highly variable still on the cool side. From the weather stations at the branches, these are the soil temperatures at 2.5 inches, from April 20 were:
county research branch temperature (f) Jackson Jackson 51.1 Noble Eastern 51.8 Piketon Piketon 49.3 Clark Western 50.6 Huron Muck Crops 45.5 Ashtabula Ashtabula 32.1 Sandusky North Central 47.0 Wood Northwest 40.8 Clark Western 50.6
Cool, wet soils promote the growth of one of the major seed and seedling pathogens of corn and soybean, Pythium. Some or the more than 25 different species of Pythium are particularly favored by these cooler temperatures. Since the soil is moist, oospores which overwinter, are germinating. When the soils become saturated, they will form a structure called a sporangium which forms the zoospores. What is unique about this group of pathogens compared to watermolds is that these spores will then swim to the roots, they are actually attracted to germinating seeds and growing roots. When seeds are planted into cool soils, and we have some low temperature nights, the seeds themselves can be injured. This then serves to attract more zoospores – quite a system all in favor of these cool, wet loving pathogens.
I think Peter Thomison said it best in last week’s article. Plant in as close to optimum conditions as possible. Don’t try to beat a major storm front – in Ohio that is a classic set up for replant conditions. Keep monitoring those soil temperatures to ensure the best jump start for this seed. If in doubt, go back and look at the receipt for that seed, this is a huge investment for the overall farming inputs. You only want to plant once.
Well drained soil, and seed treatments with one or more of the following: metalaxyl/mefenoxam, strobilurin, or the new fungicide ethaboxam will all protect young seeds/seedlings, but to a point. Too much cold, long periods below 50 F and extensive saturated soils can overwhelm the system. Resistance to Phytophthora sojae (warmer temperature oomycete) is well studies and well known for all of the varieties that you purchase. It is not known how resistant the varieties are to Pythium spp. There are just too many to test.
Adjusting Corn Management Practices for a Late Start
As of Sunday April 20, no appreciable acreage of corn had been planted in Ohio (http://www.nass.usda.gov/oh ). Although weather forecasts call for some warmer than average temperatures and relatively near-normal rain this week, the forecast for early May is mixed with the possibility of greater rain and lower temperatures than normal. As prospects for a timely start to spring planting diminish, growers need to reassess their planting strategies and consider adjustments. Since delayed planting reduces the yield potential of corn, the foremost attention should be given to management practices that will expedite crop establishment. The following are some suggestions and guidelines to consider in dealing with a late planting season.
Although the penalty for late planting is important, avoiding tillage and planting operations when soil is wet should be a higher priority. Yield reductions resulting from "mudding the seed in" are usually much greater than those resulting from a slight planting delay. Yields may be reduced somewhat this year due to delayed planting, but effects of soil compaction can reduce yield for years to come. (Keep in mind that we typically don’t see significant yield reductions due to late planting until mid-May or even later in some years).
If you originally planned to apply nitrogen pre-plant, consider alternatives so that planting is not further delayed when favorable planting conditions occur. Although application of anhydrous N is usually recommended prior to April 15 in order to minimize potential injury to emerging corn, anhydrous N may be applied as close as a week before planting (unless hot, dry weather is predicted). In late planting seasons associated with wet cool soil conditions, growers should consider side-dressing anhydrous N (or UAN liquid solutions) and applying a minimum of 30 lb/N broadcast or banded to stimulate early seedling growth. This latter approach will allow greater time for planting. Similarly, application of P and K is only necessary with the starter if a soil test reveals the soil is below the critical level.
Keep time expended on tillage passes and other preparatory operations to a minimum. The above work will provide minimal benefits if it results in further planting delays. No-till offers the best option for planting on time this year. Field seedbed preparation should be limited to leveling ruts that may have been left by the previous year’s harvest - disk or field cultivate very lightly to level. Most newer planters provide relatively good seed placement in "trashy" or crusted seedbeds.
Don't worry about switching hybrid maturities unless planting is delayed to late May. If planting is possible before May 20, plant full season hybrids first to allow them to exploit the growing season more fully. Research in Ohio and other Corn Belt states generally indicates that late plantings of earlier maturity hybrids are less susceptible to yield losses than late plantings of the later maturing, full season hybrids.
In delayed planting situations, use the optimal seeding rates for the yield potential of each field. Recommended seeding rates for early planting dates are often 10% higher than the desired harvest population because of the potential for greater seedling mortality. However, soil temperatures are usually warmer in late planted fields, and as a result germination and emergence should be more rapid and uniform. So, as planting is delayed, seeding rates may be lowered (decreased to 3 to 5% higher than the desired harvest population) in anticipation of a higher percentage of seedlings emerging.
Spring Insect Concerns Already?Author(s): Andy Michel
It is difficult to even think about insects when many producers have not even had a chance to work the fields, let alone plant. However, two items of note to think about over the next week or two. First, we are actually approaching the required number of growing degree days needed for peak activity of alfalfa weevil in our southern counties.
The main damaging stage is the larvae, which feed and injure the plant through defoliation. As a reminder, alfalfa weevil scouting is accomplished by collecting a series of three 10-stem samples randomly selected from various locations in a field. Place the stem tip down in a bucket. After 10 stems have been collected, the stems should be vigorously shaken in the bucket and the number of larvae in the bucket counted. The shaking will dislodge the late 3rd and 4th instar larvae which cause most of the foliar injury. Close inspection of the stem tips may be needed to detect the early 1st and 2nd instar larvae. The height of the alfalfa should also be recorded at this time.
Economic threshold is based on the number of larvae per stem, the size of the larvae and the height of the alfalfa. The detection of one or more large larvae per stem on alfalfa that is 12 inches or less in height indicates a need for rescue treatment. Where alfalfa is between 12 and 16 inches in height, the action threshold should be increased to 2 to 4 larvae per stem depending on the vigor of alfalfa growth. When alfalfa is 16 inches in height and there are more than 4 larvae per stem, early harvest is recommended. See the OSU alfalfa weevil Fact Sheet athttp://ohioline.osu.edu/ent-fact/pdf/0032.pdf for more information on the insect. For insecticides that are labeled for alfalfa weevil, see http://entomology.osu.edu/ag/images/Alfalfa_Weevil%281%29.pdf . As the temperature warms, alfalfa fields in the more northern part of the state will need to be scouted.
Secondly, a silver lining to the cold weather may be a decrease in bean leaf beetle populations early in the season. BLBs overwinter as adults, and typically do not do well in extreme cold winters. Like many other states, we are predicting a relatively low BLB populations; however this may change depending on planting conditions and timing. BLB is becoming one of our more serious pests on soybean so early planted fields will still be susceptible and will need scouting.
This Week's Weather
The week of April 21-26 will feature temperatures a few degrees above normal with below normal rainfall. Normal highs are in the 60s and normal lows in the 40s for the most part. Normal rainfall is about 0.75 inches. We are also entering the period where we see our last freeze this week in any given year. However, as we talked about in March, we expect a late last freeze into early May this year based on years similar to this one. Much of the area will see lows on Wednesday this week near freezing.
The week of April 27- May 3 will be much cooler than normal and wetter than normal. However, confidence is low to moderate in this period with significant weather uncertainty. There is more confidence of being chilly than wet. Temperatures will likely be 5-10 degrees below normal at least in this period. More freezes are expected from April 27-29 across the state of Ohio. A wetter weather system is possible by the middle to end of the week about April 30-May1. There is a low chance of some mixed wet snow on the northwest side of the storm later next week but again confidence is low on that but there is a low risk of that occurring.
All of this means soil temperatures will remain somewhat below normal into early May.
Going forward, May appears to be cooler than normal for the start of the month but will end warmer than normal. Rainfall after the first few days appears below normal for several weeks of the month until possibly the end of the month.
Summer still looks uncertain with the tendency toward near normal temperatures and near or slightly drier than normal weather.
Finally, indications are an El Nino may be in the process of forming. Research by OHRFC and Ohio State University indicates negative impacts on crops yields during El Nino year particularly corn. However, since this El Nino was not going in early spring already and the lag to atmospheric response, impacts may be rather marginal this year.
Have You Evaluated Your Forage Stands?Author(s): Mark Sulc,
Two weeks ago Rory Lewandowski wrote an article describing how to evaluate forage stands for winter injury. So our question is, “Have you walked out into your forage stands yet this spring?” If not, you may be in for a rude surprise.
The hard freeze this past week was cause enough for concern for us to check a few fields. There is some frost dieback of the top leaves, particularly in orchardgrass (see photo http://ohioforages.blogspot.com/). But this is not the biggest problem we found.
The more serious problem we observed was severe heaving damage in alfalfa, particularly in the Wayne country area. Some fields showing heaving of 70% of the stand.
Heaving is usually more severe in areas with less than ideal internal and surface soil drainage and on soils with high shrink/swell potential. It is more likely where a mid to late fall harvest was taken. Fall harvesting can weaken plants and it reduces the plant residue that serves to moderate soil temperature fluctuations and catch snow that also insulates against wild temperature swings during the winter.
Plants with crowns heaved up 2 or more inches are probably already dead or in the process of desiccating and will soon die. Plants that are heaved 1 to 1.5 inches above the soil surface or less may on casual inspection appear normal and be greening up. But closer inspection will reveal crowns above the soil surface, which will likely limit the productive life of the plant. Such plants will desiccate more quickly, be injured by wheel traffic, and crowns may break or be cut off at the first harvest. Some of those plants may survive through the first harvest, but their yield potential is compromised and they will likely disappear from the stand at some point during the growing season.
We also observed severe winter injury in some perennial ryegrass varieties and even in some white clover varieties in our trials. Time will tell how much they will recover, but the winter damage was quite substantial in some varieties, including an older perennial ryegrass check variety we use in our trials.
A careful inspection of all alfalfa and other forage stands at this point in time is very important. A “windshield inspection” is inadequate to accurately assess the health of alfalfa stands this year. Walk your fields and get a broad view to determine whether spring growth appears uniform. If growth is spotty or nonexistent, it is very likely that plants have suffered some injury or heaving.
Visually estimate the ground cover of desirable forage plants as the stand develops 4 to 6 inches of new growth. Stands with more than 80% ground cover and good vigor should produce excellent yields assuming good growing conditions, stands with 60-80% ground cover should produce fair yields, stands with 40 to 60% ground cover will probably produce yields in the 60% range of normal, and stands of 20-40% ground cover will yield less than half their normal potential. Weeds will become a real problem in the thinner stands, and over seeding with Italian ryegrass or with oats will boost first harvest yields. Destroying the stand and rotating out to another crop should also be considered where substantial damage has occurred.
Be Mindful of Bees during Delayed Planting this SeasonAuthor(s): Andy Michel
(Editor's note: Reed Johnson is the lead author on this article) Beekeepers in Ohio suffered substantial losses of colonies over the exceptionally long and cold winter of 2013-2014. Here in Wooster we lost more than half of our colonies and beekeepers around the state are reporting levels of winter kill in the 30-80% range. While the frigid temperatures played a substantial contributing role, losses were undoubtedly made worse by all of the problems facing bees today: parasites, diseases, pesticides, breeding problems, and a general lack of summer and fall forage.
Spring is the only reliably good season for bees in Ohio. Colonies that survived the winter and new colonies brought up from the Gulf Coast are in the process of harvesting nectar and pollen from spring-blooming trees and weeds -- but little honey will be made. This spring bounty will be eaten by the bees themselves as they multiply and grow into large productive colonies that will be able to make a honey crop off of clovers, black locust, alfalfa and possibly soybean in the coming months. Additionally, robust colonies are needed to pollinate the fruit trees soon and pumpkins, squash and cucumbers later in the summer.
This spring build-up of honey bee colonies can be directly threatened by corn planting. Insecticide seed treatments used on corn seed produce an insecticidal dust when they are planted. Depending on conditions, this insecticidal dust can settle on the flowering trees and weeds that bees are visiting. Insecticidal dusts are terrible for honey bees because they do not immediately kill the bees visiting flowers. Rather than causing immediate death, the dust is packed up with the pollen and brought back to the colony where it is can poison young and developing bees inside the colony.
In spring 2013 we sampled pollen from three bee yards in Madison, Union and Clark Counties. During corn planting all colonies were bringing back pollen containing corn seed treatment insecticides, sometimes at levels that would be expected to cause bee death. While no obvious bee-kills were observed in our colonies in 2013, we believe that different conditions during planting could have led to a different outcome. In 2013 corn planting in central Ohio coincided with the start of bloom for fruit trees and hawthorns – extremely attractive flowers for bees – which likely drew bees away from the riskier and somewhat less attractive dandelions, mustards and purple deadnettle growing in corn fields and on field margins. In some years planting may happen before or after fruit tree bloom when bees are intensely interested in weeds growing in and near fields. This may have been the case in Ohio in 2012 when planting started early and a number of bee-kill incidents were reported.
Winterkill of Italian Ryegrass StandsAuthor(s): Mark Sulc
(Editor's note: John McCormick was also an author on this article) Last week we observed the worst winter injury in Italian and annual ryegrass stands since 2004 when we first began testing this species on an annual basis. We have received several reports of cover crop stands of annual ryegrass that did not survive the winter at all. Do continue to monitor those stands for recovery, as a burndown herbicide may still be needed if there are some surviving tillers.
We planted 32 different varieties of annual and Italian ryegrass on 16 September 2013 at the Western Agricultural Research Center near South Charleston. Of the 32 varieties, only four showed somewhat acceptable spring vigor and stand density, and even those sustained some damage along the west side of the plots (see accompanying images).
The four varieties that had significantly lower winter injury ratings than the rest were Winterhawk (marketed by Oregon seeds), Marshall (marketed by Wax Seed Co.), an experimental variety not on the market, and Fria (marketed by Allied Seed Co). Five to six other varieties had significant damage but may recover some, while 21 varieties appeared to be dead or mostly dead at this point in time. Marshall, which has been our check variety, has greater cold tolerance than most varieties on the market.
All 32 varieties had 100% ground cover going into the winter and we harvested them for forage yield last November (see results athttp://oardc.osu.edu/forage2013/table10.asp).
On Monday the 21st of April, the only real change in the appearance of the plots was that winter annual weeds are becoming more obvious. We observed no substantial differences in recovery of the varieties from 10 days ago when the pictures were taken. We will report results from this trial in this newsletter at the conclusion of the trial and in the 2014 Forage Performance Trials Report.
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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