Corn kernels at R2 (blister) — clear, blister-shaped and filling. Photo: Purdue Univ., R.L. Nielsen.

Area Update … 'Grain Fill Begins'

Driving the territory this week, the crop looks like it means business. Corn is moving from full tassel into blister (R2) and milk (R3) on the earliest fields — the pollination chapter is closing and the yield-making weeks are here.

On the soybean side, April-planted beans are running anywhere from late R2.5 into R4, and staging varies with maturity: our fuller-season varieties like P21Z71E are a step behind the P16Z25Es, which are the furthest along. Every day of sunshine and every timely rain from here builds pods and fills kernels. Here's where the numbers stand and what we're watching.

GDU Accumulation

Since Apr 15 planting the territory has banked 1,612 GDUs, running 6% ahead of the 15-year trend. The chart shows the running departure day by day - green when we're ahead, gold when we're behind.

Rainfall

Season rainfall since Apr 1 stands at 14.4" against a normal of 17.8" - 19% behind normal. Locally notable this week: St. Peter caught 5.24" while Madison Lake saw only 0.17".

Solar Radiation

Solar radiation since Apr 1 is 6% ahead of normal for the season. Sunlight is the fuel for grain fill - a sunny stretch from here adds test weight, while a cloudy one trims the top end.

Full town-by-town GDU and rainfall reports are attached to this email.

Radiation: Open-Meteo ERA5, daily shortwave sum, 44.116°N 93.708°W. Yields indexed to a fitted trend — no absolute yields shown.

Why We Track Sunlight in a Seed Newsletter

A fair question we've gotten: why is solar radiation in a seed newsletter? So we checked it against our own record. We pulled daily solar radiation back to 2008 for coordinates just outside Janesville and set each June against corn yields for the same years — with the long-term yield trend removed, so we're asking whether a year came in above or below where the trend said it should.

Of every month we tested, June was the only one that held up. August came back at essentially zero, which makes sense — by then the crop is in grain fill and what limits it is water and heat, not light. June is canopy building and the run-up to pollination, when the plant is still deciding how big a factory it's going to be. Roughly, every extra 100 MJ/m² of June sunlight has been worth about 19 bushels of trend deviation.

Now the honest part. June light explains about a third of the year-to-year swing — meaning two-thirds is something else. The red dots on the chart are years the pattern missed: 2023 was the 4th brightest June on record and still finished below trend; 2019 and 2014 were far worse than a dim June could account for. The asymmetry is the real lesson: a dim June is a decent warning, but a bright June is not a promise. Good light gets the canopy built; it buys no insurance against a dry August.

Where 2026 lands: June came in at 718 MJ/m², 106% of the 18-year normal — 8th brightest of 19 years. That points to a crop modestly above trend, with a wide range around it. A tailwind, not a guarantee. August still has the final say.

Estimated Black Layer Dates

Projected black layer dates for our top products, using actual territory GDUs banked to date (Apr 15 planting: 1,612 and Apr 22 planting: 1,562 and Apr 29 planting: 1,509 and May 6 planting: 1,482) plus 15-year average accumulation the rest of the way. Every product listed has already silked. Cooler-than-normal weather from here pushes these dates back; heat pulls them ahead. Planted outside these windows? Call me and I'll run your date.

Checking Pollination — The Shake Test

Five to seven days after silks emerge, you can grade pollination yourself: carefully unwrap the husks from an ear and give it a gentle shake. Silks that drop off are fertilized; silks that hang on are not. Heat-stressed ground, sands, and compacted headlands are where you'll find silk-tassel timing problems first. If a field looks questionable, give us a call before you finalize late-season input decisions on it.

Japanese beetles and their lacy, skeletonizing feeding — looks worse than it usually counts.

Insect Watch — Aphids Quiet, Japanese Beetles Not

Soybean aphids: numbers have been almost nonexistent this year — good news, but not a reason to quit looking. Keep scouting through R5 (beginning seed); the number to act on is 250 aphids per plant on 80% of plants and climbing. If a spray ever is warranted, remember pyrethroid-resistant aphids are widespread in Minnesota — know your mode of action.

Japanese beetles: the opposite story — we're seeing heavier infestations this year, especially in fields closer to towns where the grubs overwinter in turf. Our main concern is defoliation in soybeans: they tend to skeletonize leaves in the upper canopy, which looks alarming, but it takes about 20% defoliation after bloom to justify a spray — and the damage almost always looks worse than it counts. Check field edges first; that's where they pile up before moving in.

Corn rootworm beetles: these are the silk-clippers to watch during pollination — treat if silks are clipped to under 1/2 inch with beetles still active and pollination less than half complete. We haven't seen silk clipping to any real degree yet, but keep an eye on it.

Disease Tracker — Where Things Stand

Each week during the season Pioneer scientists publish disease tracker maps built from field observations and modeling. Here's the latest read for our part of the world as of July 14. Use these as a heads-up on what's moving in the region — then confirm with your own boots in your own fields, because pressure varies field to field.

On these maps, green is good: dark green is very low risk and the colors climb through yellow and orange to dark red for very high risk. Our territory is sitting comfortably in the low-risk green right now.

Tar Spot

Grey Leaf Spot

Northern Corn Leaf Blight

Southern Rust

A Tip of the Hat

Many of you read Jay Zielske's Pioneer Agronomy Update for years — Jay hung up his boots June 30th after 34 years. Those are big shoes to fill, and this weekly NHS update aims to keep timely, local agronomy info coming to your inbox every Monday. Same mission: help you make better decisions on your acres, with a little fun along the way.

Setting the new Meridian bulk bin alongside the lineup at our soybean site.

From the Field — New Bulk Bin at the Soybean Site

We've been busy at the soybean site this summer — a new bulk bin is now standing tall in the lineup! In a normal year we sell far more soybean units than we can hold on site at one time, so this bin gives us the capacity and flexibility to bring in additional varieties in bulk and to turn our seed bins multiple times through the season. Practically, that means once we start treating soybeans, we can bring in more bulk beans in a timely manner — so the varieties you want are treated, staged, and ready when you need them. It's an investment in serving you better, and one more reason to talk with us early about your 2027 soybean lineup.

What's Happening at NHS

Customer Appreciation is set — mark your calendars! Join us Wednesday, Sept. 9 at Quirams or Thursday, Sept. 10 at Oaks. We'll walk through a brief agronomy update, hybrid information, and what we're seeing across the territory this season. More details to come — call or text with any questions.

Hop on the bus — Pioneer HQ tour, Aug. 18-19! We're taking a bus trip to Johnston, Iowa to tour Pioneer headquarters — a behind-the-scenes look at where the genetics on your farm come from. We leave early afternoon Tuesday, Aug. 18 and return late afternoon Wednesday, Aug. 19, so pack an overnight bag. Spots are limited — call or text Tim at 507-995-0031 to claim yours.