TOPICS FOR THIS UPDATE:

• Temperatures & GDU accumulation update
• What’s going on in my fields right now…
• Fungicide/Diseases in Corn,
• Insect Update
• Soybean Update

TEMPERATURES & GDU ACCUMULATION:

As of July 6th, we have accumulated approximately the following for Growing Degree Units in 2025:

Planting Date     GDD’s2025          Average GDD         Departure from average

April 17                  1232                           1138                                +94 (+4 days)

April 24                 1181                            1092                                +89 (+3.5 days)

May 1                     1135                            1045                                +90 (+3.5 days)

Since the last update on June 11, we have gained 3-4 days.  Instead of slightly behind normal, we are slightly ahead of normal on GDU’s.  Kind of hard to believe considering the up-and-down nature of our temps over the last few weeks.  Below maps are 6-10 day and 8-14 day temperature forecasts.

     

These maps need to be taken with a grain-of-salt as they change daily; however, they are predicting normal temps over the next week with a warming trend into the third week of July.  Some major ag-weather sites are saying the potential for cooler temps through the first two-to-three weeks of July is high.  This is good news as far as no stress on the crops, but will possibly delay silking dates as compared to normal….thereby increasing potential for later-maturing crops vs. last few years.  More on this in the next section….

What’s going on in my fields?

• The corn crop in our area looks very good at present time.   Overall color is still good considering the amount of rain some areas have had over last two weeks.  Much of the corn crop is in the V12-V15 stage, which is tracking very close to normal and one leaf stage behind the 2024 growing season.   From V10-VT, corn gains a new leaf every 50 GDU’s, or about every other day.  Cooler temps will delay this to 2.5 days/new leaf.  Majority of tasseling will most likely occur from July 13-24th.  Keep in mind that hybrids silk early, or late, versus their maturity rating.  It always seems to take a little longer than expected….
• 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#.  Keep in mind that the higher amounts of rain received in some sandy soil areas may have caused some N leaching to occur.  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 from now to tassel….
• 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.  We have seen more problems with pollination under cool temps vs. warm temps.
• 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 normal temps which would give us an average of 23-26 GDU’s/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.  So far we are not seeing much for disease in area fields….a little bacterial leaf streak starting.  Keep in mind that if we see cool temperatures and wet conditions, potential disease outbreaks will increase exponentially.  We will also see a wider range of different diseases.
• So far we are not seeing any Tar Spot in the area, however, it has been confirmed in Antelope county.  So, we expect that we will see some lesions moving forward.  Hybrid tolerance is first line of defense with a fungicide giving added protection.  Pioneer offers the best hybrid tolerance to this disease in the industry.  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 P05081, P05466, P0924, P09944, P0995, P1185, P1278, P13476Q, 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…..
• 2025 Pioneer Foliar Fungicide Considerations 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 and Tar Spot. 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
• 2025 Fungicide Efficacy for Control of Corn Diseases.   This attachment shows efficacy and posted residuals by active ingredient.

Water Management

2025 has seen above normal rainfall over the last month…..up 130-200% over the last month and 200-300% over the past two weeks.   What a change from April/May!  This means that we have excellent soil moisture profiles heading 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 24-36+” (slightly below average) depending upon plant date, conditions and soil type.  Remember that maximum plant height and root depth are achieved once the plant tassels.
• Wet conditions of past few weeks has led the corn plant to be somewhat ‘lazy’ with root development, especially in the upper root structure.  Under saturated soil conditions, we expect to see some root lodged corn if a strong storm moves through the area.

Insect Update

Just beginning to see Western Bean Cutworm egg masses in sandy fields.  They are just getting flying.  Expectations are for higher pressures this growing season.

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.
• 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 P05081AML, P1122AML, P12904AML, P14830AML, & P2042AML and the new Enlist hybrids – P10625PCUE, P13777PCUE, & P1742PCUE.

Corn Rootworm

Adult beetle emergence will begin soon, if not already occurring….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.
• 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.  The new Vorceed CRW technology has been shown to give 98% beetle control.  We will watch for this trend over next few weeks.
• We are seeing some rootworm feeding from larvae in a few fields.  This may contribute to increased chances for root lodged corn under saturated soil conditions.

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

Dectes Stem Borer.…Be aware that adult beetles have been emerging over the past weeks and have been migrating into area soybean fields….much as they have in the past few years….no treatment guidelines at this time….just more for you to be aware and watch as the year progresses.

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….especially in those fields planted mid-April and with early maturity varieties.  Most fields are finally coming around and growing.  No-till and later-planted fields have been slow to ‘get going’ this year.
• 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 as area rains have been spotty ove the past week or so and they may 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, the first planted, and going on this week for later planted acres) 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….and so far, we have had weather conditions conducive for higher outbreaks of disease, both soybeans and corn.  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 two years ago.  For White mold management see attachment:  Managing White Mold in Soybeans  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….2025 Soybean Foliar Fungicide Efficacy Chart

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

Starman Seed & Supply, Inc.