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 1st, we have accumulated approximately the following for Growing Degree Units in 2026:

Planting Date     GDD’s2026          Average GDD          Departure from 30-yr average            2025

April 16                  1161                          1036                                +125                                                1116

April 21                  1117                          1005                                +112                                                1083

April 25                 1057                          976                                 +81                                                   1049

May 1                     1048                          937                                 +109                                                1003

May 8                    990                            875                                 +115                                                 920

Overall GDU accumulation has slipped some from the last update on June 11th.  The second half of June average temperatures were off by 4 degrees.  So far, 2026 is currently running 4-5 days above the 30-year average and very similar to 2025 and the 10-year average.  Even though the last half of June was cooler than normal, we are still on track to tassel/silk at normal dates.

         

Above are the 6-10 and 8-14 day temperature outlooks as of July 1st.  These change every day, so take with a grain-of-salt.  However, temperatures are trending to be above normal for the next two weeks.  Warm temperatures and full sun are always a positive….

What’s going on in my fields?

• General conditions and Silking: The corn crop in our area looks very good at present time.   Overall color is good, holding up much better than last year at this time. Much of the corn crop is in the V11-V14 stage, which is tracking very close to normal and slightly ahead of 2025.   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 be 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….see graph below for predicted silk date, etc., using current conditions and the 10-year average….planting date for the graph is April 21st, using a 113 day maturity hybrid….this is showing a silk date of July 17th…
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• Kernels per row begin around V12 and will continue 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 this week 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….
• Tasseling/Silking: 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 the week of July 13-21st.  Expect some unevenness in tasseling/silk emergence in many fields due to the heavy residue/dry soils causing slow emergence this spring.
• 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 above normal temperatures 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, overall levels of disease are very low in the area…even bacterial leaf streak is below normal. Keep in mind that if we see cool temperatures and wet conditions, potential disease outbreaks will increase exponentially, and we will also see a wider range of different diseases.
• Tar Spot has been found throughout our area, but lesions are very low at present time and not easily found.  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.  The two graphs below are related to Tar Spot and disease in general and give us something to watch for as we progress in the growing season:
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• The first graph is daily GDU accumulation using an April 21st planting date.  Main thing to note is the lower temperatures in the last half of June.  These two weeks were very conducive for Tar Spot  and Northern Corn Leaf Blight development.  These two weeks have set up Tar Spot to be heavy in the area once again.  However, if temperatures stay high and humidity is low over next few weeks, development will be slower compared to last year.
• The second graph shows accumulated leaf wetness hours for Elgin over the past ten years using April 21st planting date.  Leaf wetness is an indicator for disease development and severity. The more hours a leaf stays wet, the higher incidence of disease infestation.  Main thing to note is how 2025 was the worst year over the past 10 years…how it climbed all year long, this was due to both environmental conditions and high rainfall. Now note that as of July 1st, 2026 is trending in that same direction….                                                                In other words, our fields are set up for both development of, and high incidence for, disease, as the year progresses.
• We will keep you posted on this disease as the year progresses….   See slides below:
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• We have yet to see much for Southern Rust.  Hopefully, we will not see the same levels in 2026 as we have seen for the past two years.  Remember that this disease does not overwinter in our area and much move up from the south….
• If you are planning on only one fungicide application, the best timing for this application is VT-R1, 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, P09944, P0995, P09076, P1185,  P13476, P13050, P1413, P14830, & P15517, P1742 are hybrids to focus on first for higher probability of response from foliar fungicides…..
• 2026 Pioneer Fungicide Considerations for Corn ….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….and with Tar Spot now fully in the area.
• See attachments on disease and fungicide management – Maximizing Foliar Fungicide in Corn
• 2026 Corn Foliar Fungicide Efficacy  This attachment shows efficacy and posted residuals by active ingredient.

Water Management

With the recent rainfall over the past two weeks, 2026 has just now reached normal precipitation for the year.  Heading into mid-June we were still 4+ inches short of normal, however, we are up 200% over normal since then, which brings us close to the norm….and the rains have allowed for good penetration and fill into the second and third foot of the rootzone.

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 ET rates under cool and cloudy conditions.
• ET rates over the past two weeks have been slightly below average…. .20-.23/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, as ET rates will move to .30+ through the next few weeks.
• At present, we are seeing fairly good root depth according to the soil moisture probes….sandier soils are 20-28″, very similar to last year, and heavy soils are 24-36+”, depending upon plant date, conditions and soil type.  Remember that maximum plant height and root depth are achieved once the plant tassels.  It does appear that plant height will be taller than last year….also hoping that rooting depth and root volume will be greater than last year.

Insect Update

Western Bean Cutworm egg masses should begin to be found in sandy fields this next week.  They are just starting to fly.

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 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,P14830AML, & P2042AML and Enlist hybrids that end with PCUE behind the hybrid number.

Corn Rootworm

Adult beetle emergence will begin soon….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.

Dectes Stem Borer.…Be aware that adult beetles have been emerging over the past week 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.

European Corn Borer….Much of the conventional yellow and white corn hybrids and popcorn have seen low-to-moderate levels of ECB larvae.  If you have not treated yet, recommended that you treat ASAP.

Soybean Development

• Most of the soybeans in our area are at R1 (Beg flower) to R2 (Full flower).  Most fields are finally coming around and growing.  No-till and later-planted fields have been slow to ‘get going’ this year, as normal….
• 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 usually 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 somewhat spotty over the past two weeks 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 going on the first planted, and going on this upcoming week for later planted acres) and/or later at R3 (pod set) stage of growth.  Environmental conditions over the next two months will determine disease incidence and overall level of disease infestation….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. For White mold management see attachment:  Managing White Mold in Soybeans  Highly recommended to apply a fungicide for white mold to most acres, especially those fields with a history of white mold in the past.  Apply Viatude, Aproach, or Delaro for best control (really, ONLY control)….for white mold….2026 Foliar Fungicide Efficacy in Soybeans

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

Starman Seed & Supply, Inc.