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Corn Newsletter : 2019:16
Average Fall Freeze Dates for Corn Considerations
In last week’s C.O.R.N. newsletter, Peter Thomison provided useful information on tools available for switching corn hybrids (https://agcrops.osu.edu/newsletter/corn-newsletter/2019-15/more-switching-corn-hybrid-maturities). As Dr. Thomison points out, Dr. Bob Nielsen at Purdue University wrote an article describing the U2U Corn GDD Tool, available from the Midwest Regional Climate Center (https://mrcc.illinois.edu/U2U/gdd/), with caveats to keep in mind as one is making their decisions. Specifically, users are encouraged to modify their black layer GDDs within the tool in order to reflect a more accurate assessment of days to maturity.
To aid in these decisions, we have provided two maps below showing the average median date of the first fall freeze (based on 1981-2010 conditions) for selected sites across Ohio. Figure 1 shows the median date based on 32°F and Figure 2 shows the median date based on 28°F. Figure 1 shows that most of Ohio experience the first 32°F date between October 11 and October 20, with a freeze occurring prior to this period for some locations (dark green circles). The average first date for 28°F occurrence in the fall is between November 1 and November 10 (Figure 2; brown circles), with many sites across West Central, Northwest, and East Central Ohio indicating dates as early as October 21.
This and other important agricultural-related data may be found at the Midwest Regional Climate Center (https://mrcc.illinois.edu/cliwatch/special_topics/agriculture.html).
Using the Corn Growing Degree Day Decision Support Tool to select appropriate hybrid maturities for June
The Corn Growing Degree Day decision support tool allows one to choose any Corn Belt county, enter the planting date and hybrid maturity, and generate a graph that shows projected GDD accumulations through the season, including the date on which you can expect that hybrid, planted on that date in that county, to mature (achieve black layer). One important adjustment missing from this tool is the fact that planting corn late usually lowers the GDD needed to get a hybrid from planting to maturity. In an article on his website, Dr. Bob Nielsen at Purdue includes a calculator that adjusts the GDD requirement downward based on how late planting actually is. This is not a trivial adjustment: planting a hybrid on June 10 (vs. May 10) lowers the GDD requirement by more than 200 GDD. So a hybrid that needs 2,700 GDD to mature if planted on May 1 will require an estimated 2,428 GDD if planted on June 10 (Using Dr. Nielsen’s calculator). The revised GDD number can be manually entered into the GDD tool instead of days RM for the hybrid.
To get started on the tool, click where your farm is located in the county of interest (GDDs are calculated based on longitude and latitude) then select the graph tab. As an example, a 108-day RM hybrid (which the tool estimates will need 2,600 GDD from planting to maturity) planted on June 10 in Wood County, Ohio is projected to mature sometime after Dec 1 (the frost date is estimated at Oct. 29). However, if you manually change the expected layer GDD requirement from 2600 to 2328 (estimated using the calculator above) the GDD tool estimates that hybrid would achieve maturity by about Oct. 8 (nearly three weeks before the first average freeze).
If we change the planting location to Wayne County, OH using the same hybrid and planting date and make the appropriate input changes to the GDD tool regarding reduced GDD requirements for a delayed planting, the GDD tool estimates that the hybrid wouldn’t achieve maturity until November 7 (average frost date of Oct. 27). Changing to a 102-day hybrid there would move projected maturity to October 9.
For more information on late planting issues, check out the following:
Nafziger, E. 2019. Dealing with very late corn. The Bulletin – University of Illinois. URL: http://bulletin.ipm.illinois.edu/?p=4622
Nielsen, R.L. 2019. Some Points to Ponder as You Struggle With Decisions About Late-Planted Corn. Corny News Network. URL: http://www.kingcorn.org/news/Articles_19/LatePlantedCorn.html
Switching hybrid maturities for June planting dates
Farmers who still anticipate planting corn for grain production should review their hybrid maturities to minimize the risk of corn not maturing safely prior to a killing fall freeze. We would encourage the use of the Corn GDD Tool to select "safe" hybrid maturities for late planting (http://www.kingcorn.org/news/timeless/HybridMaturityDelayedPlant.html).
Although they are not planted as widely as our commonly grown maturities, hybrids with relative maturities of 100-104 day maturity are likely to achieve physiological maturity if planted by mid-June throughout most of the state. There is limited information on the agronomic performance of hybrids with maturities less than 100 days. Since these “ultra-early” hybrids were not developed to be planted in Ohio, they are regarded as less adapted to growing Ohio conditions and more susceptible to disease and stalk quality problems. Because of their questionable yield potential, ultra-earlies are typically not recommended in late planting situations.
In recent trials conducted at OSU in 2016-2017, ultra-early hybrids (90-100 day) were compared to more common CRM hybrids (104-109 day) for agronomic performance. Planting dates were May 23 and June 2 in Crawford County in 2016 and 2017, and May 23 in Wayne County in 2017. All hybrids were harvested on the same date within a site each year. Growing conditions were very favorable for corn production at these sites.
While yield and return were greatest for the 104-109 day hybrids, the return per acre was similar to the 96-100 day hybrids statistically (as indicated by the asterisks) due mainly to discounts on the 104-109 day hybrids from low test weights and high harvest moisture. The performance of the 90-95 day lines was consistently below the other groups tested but still produced substantial yield. In 2018, when planting dates were mid-May at each location, the yield and return were greater with the 104-109 day hybrids compared to the ultra-early hybrids. When considering changes to relative maturity for late planting, this may help in the decision-making process. Earlier maturity hybrids may incur less drying costs and have higher test weights, but may have a slight yield disadvantage compared to the 104-109 day hybrids. However, these results and observations are based on limited test data that may not apply across a wider range of production environments, especially those outside northcentral/northeastern Ohio.
* Greatest (or statistically equivalent to the greatest) value.
We would strongly encourage those producers to consult with their seed company agronomist before changing to hybrids with a relative maturity less than 100 days. Check hybrid disease ratings for foliar diseases (esp. gray leaf spot and northern corn leaf blight), stalk rots and ear rots as well as dry-down characteristics.
Cereal Leaf Beetles in Wheat
Populations of cereal leaf beetle are increasing in Ohio. Although adults can feed on wheat, the larvae do most of the damage. These larvae are small, gray and moist, and are covered with a substance resembling bird droppings. Damaged wheat appears “frosted” as the cereal leaf beetle feeds and strips away leaf material. Wheat fields are best inspected using a sweep net or by walking the field. Infestations exceeding 2 larvae per stem may require an insecticide treatment to prevent further loss.
Insecticidal Seed Treatments in Late-Planted Crops
Many producers are planting late this year due to continued wet weather and may be wondering how insecticidal seed treatments should factor into their planting decisions. While individual situations vary, here are some rules of thumb to consider.
The most commonly available class of insecticidal seed treatments are neonicotinoids such as thiamethoxam, clothianidin, and imidacloprid. The conventional wisdom is that late-planted crops stand to benefit less from these products than early-planted crops. Warmer soil and air temperatures get the plant get off to a faster start and faster growth, allowing it to outpace insect pests. Another important factor to keep in mind about insecticidal seed treatments is their window of activity. The insecticide applied to the seed coat is taken up by the germinating plant and translocated through the plant in the growing tissue. The amount of product that goes on to the seed is finite – when it runs out, it runs out. Studies have shown that on average, new plant tissue added 3 weeks after planting does not contain the insecticide product. This means that pests that affect plants after the 3-week planting window will not be managed by the insecticide. Thus we do not recommend these products for use against anything but the earliest season pests (usually soil pests). We generally do not recommend insecticide seed treatments as a prophylactic against early-season bean leaf beetles. Feeding on early V soybeans is rarely economic, only cosmetic. In the rare cases where feeding may be economic (considerable stem clipping or over 40% defoliation on most plants) a foliar insecticide can be applied.
Fungicide for Scab Control: Late Application and Rain-fastnessAuthor(s): Pierce Paul
Most of the wheat fields in the northern half of the state reached anthesis last week. The remaining fields will reach this critical growth stage during this week. According to the scab forecasting system (www.wheatscab.psu.edu), the risk for Fusarium head blight (FHB; commonly referred to as head scab) has been moderate-to-high over the last 5-7 days on susceptible varieties planted in the northwest corner of the state. However, persistent rainfall, soggy fields, and difficulties scheduling an aerial application, prevented some fields from being sprayed to control scab and vomitoxin at the anthesis/flowering growth stage. But although anthesis is the recommended growth stage for head scab fungicide application, missing this window does not necessarily mean that you have lost the opportunity to use an effective fungicide to suppress head scab and vomitoxin.
If the risk for scab was high a few days ago when your field reached anthesis, but you were unable to apply a recommended fungicide, you can still make an application up to 6 days after anthesis and see good results in terms of scab and vomitoxin control. This is true for Prosaro, Caramba, and Miravis Ace. For instance, if your field of FHB susceptible wheat reached anthesis last Friday, May 31, when conditions were highly favorable for scab, but rain prevented you from applying a fungicide on Friday, you still have until the middle of this week to treat that field and achieve scab and vomitoxin control comparable to what you would expect had the field been treated on Friday. Applications made 4-6 days after anthesis are effective against vomitoxin and are particularly useful when the weather following anthesis is consistently favorable for scab. In fact, even if the scab risk had decreased from Friday to now, a late application would still be warranted, given that conditions were favorable for scab during the week leading up to anthesis.
Based on our research, both Prosaro and Caramba are very rainfast, and I suspect that Miravis Ace may be as well (based on the fact that propiconazole, one of the active ingredients in Miravis Ace, is very rainfast). Regardless of which of the three fungicides you choose to use to manage scab and vomitoxin, just make sure that they are applied at least an hour before it starts to rain, use a nonionic surfactant, and follow the labels.
Agronomic Field Day June 20Author(s): Alan Sundermeier, CCA
The Northwest Ag Research Station will be hosting a field day on June 20 at 9 am emphasizing “Lake Friendly Farming Research”. Topics include Soil Drainage research, precision fertilizer placement, ultra-early corn, manure nutrient balancing, and soil health. Management of prevented planting fields will also be discussed. RSVP for lunch, no cost to attend. See the flyer or www.wood.osu.edu for information.
About the C.O.R.N. Newsletter
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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