AGRONOMIC UPDATE: July 10, 2024…wet spring into cool summer so far….

Topics:

– Growing Degree Day Update/Forecast Maps

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

– Fungicide/Disease in Corn

– Insect Update

– Soybean Development

As of July 9th, we have accumulated approximately the following for Growing Degree Days in 2024:

TEMPERATURES & GDU ACCUMULATION:

Planting Date GDD’s2024 Average GDD Departure from average

April 23 1288 1298 -10 (even)

May 5 1192 2012 -20 (-1 day)

Current GDU’s are running average, to slightly behind average. Last year at this time we had 1374 GDU’s accumulated, which means that we are 4 days or so behind 2023. The first week of July in 2024 has seen much below average temperatures, 6-8 degrees below average to be in fact. This is delaying tassel/silking by a few days compared to the last few years. We will be tasseling more like normal, to slightly behind normal.

What’s the forecast for the next two weeks?

The above maps are the temperature and precipitation forecasts for the next 6-10 and 8-14 day periods. The maps (which were issued July 9), are forecasting an increase in heat with normal precipitation through this period. This would be good as it ‘feels like’ we are behind in crop development….

What’s going on in my fields?

Baring the fields that were caught in Sunday’s hail event, much of the corn crop looks good overall. However, most all fields in the area have spots of reduced stand from erosion, waterholes, etc., from the spring rains. Much of the corn crop is in the V13-V16 stage to almost VT, this is slightly behind last year. From V10-VT, corn gains a new color every 50 GDU’s, or about every other day. During last week’s cooler temps, it was taking three day for a new leaf to emerge. Many fields will begin tasseling the end of this week, with most fields reaching full tassel mid-next week. Majority of tasseling will occur from July 12-20th, which is behind last year by a few days.
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 is very rapid now through tassel (up to 4-8 lbs per day). As we have discussed in the past, 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….40-50#. Due to the increased rainfall this spring and into June/July, it is safe to assume that some N leaching occurred on the sandy soils. Keep this in mind as you determine your final N applications. Overall color, however, looks very good throughout the area….
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 5-10 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….this will take place next week for most fields. Expect some unevenness in tasseling/silk emergence in most fields due to the spring rains moving crop residue around and slowing 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….. Crop Focus – Corn Pollination Success
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 (R1) 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 above normal temperatures, which should give us a GDD accumulation of 25-30 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, thereby lowering potential final yield.

Corn Leaf Disease/Fungicide

The next four to six weeks will be critical for disease infestations and fungicide applications. The weather conditions experienced so far this year has increased the likelihood of seeing higher incidence of disease for the 2024 crop. Keep in mind that if we continue to see cool temperatures and wet conditions, potential disease outbreaks will increase exponentially. We will also see a wider range of different diseases.
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, however, we have seen some Northern Corn Leaf Blight lesions and, with the wet conditions, we are starting to see the first Common Rust show up.
We are not seeing any Tar Spot in the area, however it has been confirmed in the counties just east of us. So, we expect that we will see some lesions moving forward. Hybrid tolerance is first line of defense with a fungicide giving added protection. We will keep you posted on this disease if we find it…. See slides below:
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 at this time and has the highest demand for energy. 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 P05466, P0622, P0924, P0908, P0995, P1185, P1278, P1366, P13050, P14830, & P1563 are hybrids to focus on first for higher probability of response from foliar fungicides, especially if gray leaf spot infestations are high…..2024 Corn Fungicide Management Guide ….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. Highly recommended to fungicide corn with current weather conditions….
See attachments on disease and fungicide management – Maximizing Foliar Fungicide in Corn
Fungicide Efficacy for Control of Corn Diseases This attachment shows efficacy and posted residuals by active ingredient.

Water Management

2024 has seen above normal rainfall from planting up to now….in many cases 200% above normal. This means that we have excellent soil moisture profiles into pollination, which is a real positive to the dryland and limited irrigation acre.

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 with low humidity….lower under cool and cloudy conditions.
ET rates over the past two weeks have been average…. .20-.25/day depending upon temperatures, etc. However, we are reaching peak water use in corn, and with the potential higher temps forecasted out two 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 20-32″, very similar to last year, and heavy soils are 28-40+” (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

Just beginning to see Western Bean Cutworm egg masses in sandy fields. They are just getting flying. 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 again have pheromone moth traps located west of Elgin. Current numbers are slowing trending upwards, but too early to tell how heavy the flight will be.
Treat when the fields are 95% tasseled. Use high rates (5-6oz) 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, so this means the later planted and later silking fields have the highest potential for infestations. Cool conditions will delay and extend their flight, so what may appear low numbers now can pickup in two weeks, which is why we recommend the extra residual.
Once a field has been tasseled, any egg masses that hatch will see the larvae move 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, P0908AML, P1122AML, P12904AML, P1366AML, P14830AML, P1563AML, & P2042AML.

Corn Rootworm

Adult beetle emergence is also beginning 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. Males emerge first and this is what we are mainly seeing right now.
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, which can be upwards of 30 days. As far as timing for control, it is best to wait until there are pregnant females present.

Grasshoppers….seeing very small grasshoppers in many sandy fields. Numbers are low and defoliation is very minor….

Soybean Development

Most of the soybeans in our area are at late-R1 (Beg flower) to late-R2 (Full flower). I would not be surprised to see early R3 (pod set) on some fields end of next week. Most fields are finally coming around and growing.
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 see this happening on the soil moisture probes in the area. Heavy soil moisture profiles are full enough that very limited irrigation will be needed on soybeans through July, unless temps turn off hot. Sandy soils will need monitoring during the upcoming heat and will need a shot of irrigation to keep growth moving.
We continue to see a yield response from a fungicide application in soybeans, either at R1/R2 for white mold (applications of which should be on or going on) 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. Just a reminder, keep an eye out for Frogeye Leaf Spot in soybeans as not all fungicides control this disease. This disease is normally not an issue in our area and many varieties have very good tolerance to this disease. See attachment for more info on this disease….Frogeye Leaf Spot in Soybeans
Recent weather conditions have increased the potential for White Mold. If current weather trends continue into August, expect White Mold outbreak to be as high as a year ago. For White mold management see attachment: Managing White Mold in Soybeans
The below picture shows precipitation and temperatures for the past 30 days. This year has HIGH potential for white mold outbreak….every bit as heavy as we saw in 2023 or worse. Highly recommended to apply a fungicide for white mold to most acres. Apply Viatude, Aproach, or Delaro for best control…really, only control….for white mold….

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

Starman Seed Service, Inc.