AGRONOMIC UPDATE – July 9, 2021….Sex in the Corn Field….

I knew that title would generate some interest…..it’s not what you are thinking!

Fun fact: A single tassel produces approximately 5+ million pollen grains….

Topics:

– Growing Degree Day Update

– What’s going on in my fields?…..Corn Development, etc.

– Fungicide/Disease in Corn

– Insect Update

– Soybean Development

As of July 9^th, we have accumulated approximately the following for Growing Degree Days in 2020:

Planting Date GDD’s2021 Average GDD Departure from average

April 24 1294 1159 +135 (+3 days)

April 30 1240 1141 +98 (+2 days)

May 6 1161 1099 +67 (+2.5 days)

We have lost a couple of days compared to normal since the last update at the end of June. Other than over the 4th of July weekend, temperatures have not been as warm as predicted and humidity levels have been more like normal for this time of year. So far we have been lucky to dodge any storm damage….hopefully this trend will continue.

Based on the above numbers, when can we expect to silk? If we look at P1366 genetics we see that it takes approx. 1380 GDU’s to silk, this means that we would be looking at a potential silk date around July 12-15. Hybrids such as P0622 (1270 GDU’s to silk) are close to tasseling and should be pollinating next week. In other words, we can expect to see most all fields begin tasseling next week, with heavy pollination shed occurring mid-next week into the following week. This is slightly ahead of the average and of last year.

What’s going on in my field?….

Overall much of the corn crop looks very good! Very good color and uniformity for the most part. Much of the corn crop is in the V14-V16 leaf stage, with some tassels beginning to poke out along tree lines, etc., depending upon hybrid and planting date. This is slightly ahead of last year. From V10-VT, corn gains a new color every 50 GDU’s, or about every other day.
Kernels per row began around V12 and is continuing through and up to tassel stage
Nitrogen needs will continue to grow through tasseling and into early reproductive stages. Nitrogen uptake in corn – very rapid now through tassel (up to 4-8 lbs per day). Today’s hybrids use nitrogen later in the growing season and into the reproductive phases. You will want to keep that last shot of N available for after tasseling. This year so far, we haven’t experienced conditions that usually lead to N loss from leaching or denitrification….overall color looks great! Expectations are that more N is potentially available in the soil profile.
We are now into the rapid growth and accumulation of dry matter by the plant. The window for brittle snap is still open over the next 7-10 days.
Under field conditions, pollen shed usually occurs in the late morning and early evenings.
Pollen shed will extend for one to two weeks, but if field is uniform in plant emergence and height, pollen shed is 80% complete in 5-7 days from full tassel emergence.
At tassel, vegetative development is now complete; maximum plant height and root depth is achieved.
VT overlaps with R1 (silking stage) when visible silks appear before the tassel is fully emerged. By definition, growth stage R1 (Abendroth et al., 2011) for an individual ear is defined when a single silk strand is visible from the tip of the husk. An entire field is defined as being at growth stage R1 when silks are visible on at least 50 % of the plants. This whole field definition for growth stage R1 is synonymous with the term “mid-silk”.
A captured pollen grain takes about 24 hours to grow down the silk to the ovule for fertilization.
Peak pollen shed usually occurs in mid-morning. Some research indicates that pollen shed decreases after temperatures surpass 86F. A second “flush” of pollen often occurs in late afternoon or evening as temperatures cool. Pollen shed may occur throughout most of the day under relatively cool, cloudy conditions….. https://www.pioneer.com/us/agronomy/corn_pollination_success_cropfocus.html
Weather conditions influence pollen shed. If the anthers are wet, the pores will not open and pollen will not be released. Thus, on an average summer morning following a heavy evening dew, pollen shed will not begin until the dew dries and the anther pores open. Similarly, pollen is not shed during rainy conditions. Cool, humid temperatures delay pollen shed, while hot, dry conditions hasten pollen shed.
Generally 2-3 days are required for all silks on a single ear to be exposed and pollinated, with the silks on the butt of the ear emerging first. The silks will grow from 1-1.5 inches each day and will continue to elongate until fertilized. If not pollinated, silk elongation stops about 10 days after silk emergence due to senescence of the silk tissue. Unusually long silks can be a diagnostic symptom that the ear was not successfully pollinated.
Silk emergence and growth is dependent upon turgid pressure within the plant, in other words how much water is available in the plant to cover all of its needs. If this is limited, (ie. dryland, low-gallon wells, etc.) silk emergence will be slowed and delayed with potential to miss the pollen shed. Under severe water stress conditions pollen shed will still take place like normal, however, silks can be delayed, which means potential for poor pollination.
It takes approximately 55-60 days from silking to physiological maturity. So if a field is silking on July 15^th, it will need until September 15^th to reach maturity, given average weather. Current 6-10 and 8-14 day forecasts call for slightly above normal temperatures, which should give us a GDD accumulation of 26-27 GDU’s per day.
High nighttime temperatures (ie. any stress) begin to play a role in final yield during grain-fill as this causes the plant to work harder to maintain both yield and overall plant health.

Corn Leaf Disease/Fungicide

The next four to six weeks will be critical for disease infestations and fungicide applications.
Begin scouting now and through the next few weeks for disease infestations. So far, leaf disease load in area cornfields is very low, mainly bacterial leaf streak (see attachment below). Bacterial Leaf Streak incidence is the lowest we have seen over the past few years. However, overall temps and humidity levels the past couple of weeks have been conducive for an increased development of leaf diseases.
If you are planning on only one fungicide application, the best timing for this application is after pollination as the crop is working the hardest and has the highest demand for energy at this time. We want to protect as much of the leaf surface as possible in this time frame, which is from pollination and the two weeks after. Corn on corn acres are always a good place to start with fungicide applications.
While any hybrid can have a response to foliar fungicides, hybrids such as P0589, P0950, P1138, P1244, P1185, P1138 & P1366, are hybrids to focus on first for higher probability of response from foliar fungicides, especially if gray leaf spot infestations are high…..Fungicide response probabililty….This attachment is a list of Pioneer hybrids and their potential response to a fungicide application for Gray Leaf Spot and Norther Corn Leaf Blight. The chart also shows staygreen and stalk strength ratings for each hybrid. This chart can help with fungicide management decisions.
See attachments on disease and fungicide management – https://www.pioneer.com/us/agronomy/maximizing_foliar_fungicides_corn.html and https://www.pioneer.com/us/agronomy/bacterial-leaf-streak.html
https://crop-protection-network.s3.amazonaws.com/publications/fungicide-efficacy-for-control-of-corn-diseases-filename-2021-03-09-163332.pdf. This attachment shows efficacy by active ingredient for different leaf diseases, for the current fungicides on the market

Water Management

Below are some key water management tips to keep in mind:

The greatest yield loss from moisture stress occurs in the period two weeks prior to two weeks after pollination. For the next two weeks, the corn crop will be at its peak water usage, with ET rates of .30+ inches per day – higher when temps are in the mid-90’s and higher yet when combined low humidity.
ET rates over the past week or so have been normal to slightly above normal. Thankfully we have received some timely rainfall in this period. However, we are now fast approaching peak water use in corn, and with the potential higher temps forecasted for the next couple of weeks, it will be important to stay on top of overall water needs by the crop.
At present, we are seeing fairly good root depth according to the soil moisture probes….sandier soils are 16-28” (better than average) and heavy soils are 20-32+” (somewhat below average) depending upon plant date, conditions and soil type. Remember that maximum plant height and root depth are achieved once the plant tassels.

Insect Update

Western Bean Cutworm egg masses can be found in area, sandy fields. Keep these tips in mind over the next few weeks:

To scout for this insect, check the sandier fields first and look on the upper side of the leaf for a white, or purple, egg mass. These will be found on the upper 1/3 of the plant.
We will again have the pheromone moth traps located west of Elgin. We caught our first moths at end of this week. Check back on this website, under Grower resources, for updated moth flight counts.
Treat when the fields are 95% tasseled. Use high rates of a Capture-like product to give you 3-4 weeks of residual control.
WBC are attracted to those fields that are closest to tasseling.
Once a field has been tasseled, any egg masses that hatch will see the larvae head straight to the ear tip, so treatment soon after tasseling is critical.
AML versions of Pioneer hybrids offer control of WBC/Corn earworm. No need to treat these hybrids for WBC – these include P0622AML, P1138AML, P1366AML, P1563AML, P2042AML and P2089AML.

Corn Rootworm pressure appears to be higher this year versus the past few years. Adult beetle emergence is occurring right now, and will continue over the next few weeks. Monitor your continuous corn acres for adult beetle populations to:

prevent high numbers interfering with pollination through silk-clipping. There is a higher potential for this to occur this year than past years due to timing emergence of the adults and potential for high overall numbers of beetles.
help with rootworm control in your continuous corn acres. Strongly recommended to use Steward insecticide (by FMC) for control of adult beetle populations to help with next year’s control of rootworm. This product has shown excellent results for both kill and residual, upwards of 30 days.

Grasshoppers….seeing light feeding in both corn and soybeans from small grasshoppers. Keep monitoring for this insect if conditions stay dry.

So far we are not seeing much insect activity in soybeans. Gall Midge in Soybeans – There is a continued increase of reports of Gall Midge in the counties to the east of us. I would assume that we have this insect somewhere in our area in very light numbers. Keep an eye out for plants dying on the edges of your field, or in the end rows, as this insect is most common on field borders. See attachment for more info. https://www.pioneer.com/us/agronomy/Gall-Midge-New-Pest-In-Soybeans.html

Soybean Development

Most of the soybeans in our area are at late R1 (Beg flower) to mostly R2 (Full flower). I would not be surprised to see early R3 (pod set) on some fields next week. Most fields are finally coming around and growing….some fields are still showing leaf cupping…..crop growth is also uneven in some fields in those areas with high crop residue.
Soybeans should be nodulating heavily at this stage. At the beginning of the reproductive stage, soybeans will still put on 50% of their vegetative growth.
Crop water use in soybeans starts to increase rapidly at full flower, peaks at R3 and will stay high through R6, or full seed Flower stage is usually the time when the soybean plant begins to pull from the deeper root zones.
We continue to see a yield response from a fungicide application in soybeans, either at R1 for white mold (applications of which should be on already) and/or a later R3 (pod set) stage of growth. Environmental conditions over the next two months will determine disease incidence and overall level of disease infestation. In 2019 we saw a lot of Frogeye Leaf Spot occur in soybeans, keep an eye out on this disease as well. See attachment for more info on this disease….https://www.pioneer.com/us/agronomy/frogeye_leaf_spot_on_soybeans.html Not all fungicides control this disease, so make sure you check the label to see if this disease is controlled. Much like in corn, we are not seeing much for leaf disease pressure in soybeans at the moment.
White mold attachment: https://www.pioneer.com/us/agronomy/managing_white_mold_soybeans.html

Thank you for your business!! Please let us know any questions or concerns you may have!!

Starman Seed Service, Inc.