Agronomic Update – July 11, 2020….

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, Disease, Roots

– Insect Update

– Soybean Development

As of July 10^th, we have accumulated approximately the following for Growing Degree Days in 2020:

Planting Date GDD’s2020 Average GDD Departure from average

April 21 1327 1220 +107 (+4 days)

April 26 1274 1190 +84 (+3 days)

May 1 1223 1145 +78 (+2.5 days)

The heat of the past two weeks has really allowed the corn crop to gain ground since last update. Last update we were trending right at the normal…currently, we are trending above normal. 2020 is now ahead of 2019 for growth stage and GDU accumulation. However, this rapid growth has widened the window for exposure to green snap and we have seen some of this in the area from the recent spate of storms. As usual, it is related to many factors such as hybrid, recent N applications, field conditions, etc.

The above maps show the 6-14 day temperature and precipitation forecasts. As you can see, temperatures for much of the rest of July are forecasted to be above much above normal. This will speed up crop development. However, precipitation over this same time period is forecasted to me normal to slightly below normal. The recent rains will be a blessing during the next few weeks if the heat forecast is true.

Based on the above numbers, when can we expect to silk? If we look at P1197 genetics we see that it takes approx. 1400 GDU’s to silk, this means that we would be looking at a potential silk date around July 13-17. Hybrids such as P0688 (1280 GDU’s to silk) are close to tasseling and should be pollinating next week. In other words, due to the fact that most of the corn was planted in a 7-9 day window, we can expect to see most all fields begin tasseling next week, with pollination occurring at the end of next week into the following week. This is slightly ahead of the average.

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, 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 begin around V12 and continue 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. Expectations are that more N is potentially available in the soil profile. Also, the higher temps over the past few weeks and those that are forecasted should lead to higher N-mineralization rates versus other years, meaning a potential increase of available N to the plants.
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. The storms of the past week have led to some root lodging in spots, mainly on those hybrids with a weaker root strength score.
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 14^th, it will need until September 14^th to reach maturity, given average weather. Current forecast for the next two weeks is slightly above normal 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 not seeing much for leaf disease, mainly bacterial leaf streak (see attachment). However, overall temps and humidity levels the past week or so, 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 two weeks after pollination. (See attachment on disease and fungicide management)
While any hybrid can have a response to foliar fungicides, hybrids such as P0589, P0950, P1138, P1244, P1185, & P1366, are hybrids to focus on first for higher probability of response from foliar fungicides, especially if gray leaf spot infestations are high…..https://www.pioneer.com/us/agronomy/maximizing_foliar_fungicides_corn.html Also, corn on corn acres…. https://www.pioneer.com/us/agronomy/bacterial-leaf-streak.html

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 couple of weeks have been high. Thankfully we have received some timely rainfall in this period. However, we are now fast approaching peak water use in corn, and with the 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 12-24” and heavy soils are 20-36+” 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 should begin to show up over the few weeks. 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 moth’s just the end of this week. See this website under Grower resources for continued updated counts.
Treat when the fields are 95% tasseled. Use high rates of a Capture-like produce 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.

Corn Rootworm pressure appears to be higher this year versus the past few years. Monitor corn rootworm beetle emergence over the next two weeks for any potential silk-clipping issues.

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). Soybeans are somewhat ahead of normal for development. I would not be surprised to see early R3 (pod set) on some fields next week. Most fields are finally coming around and growing….not seeing as much leaf-cupping going on now.
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 are beginning to see this according to the soil moisture probes.
We continue to see a yield response from a fungicide application in soybeans, either at R1 for white mold or a later R3 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. It remains to be seen what the drier conditions we have experienced so far this year will mean as far as disease outbreak is concerned.
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.