WATAGA, Ill. — The current corn crop is at a yield-teetering point as plant engine grinds toward maturity.

Rod Parkinson, Wyffels Hybrids district sales manager, said there “is some great potential” with corn yields in the counties he serves, but that potential will be determined by rain during grain-fill.

Knox and Peoria counties in his district started the season with above-normal rainfall, and the impact of the early moisture on nitrogen uptake is evident.

“When I look at rainfall back in May, Knox County was definitely hit harder. Knox County was about seven to eight inches above normal — especially northern Knox County — in precipitation,” Parkinson said. “Peoria County was more like half that, four to five inches above normal.

“So, early on, I really thought Peoria County was a little better off, and they still might be. But with that being said, I think the crop still looks very good.”

A big concern has been the cooler summer and growing degree units.

“It’s kind of a little bit of a double-edged sword. It’s been rather cool, and we’re below normal on GDUs. I think we’re about 180 or 190 GDUs below normal on a 30-year average, but we’re still well above where we were in 2009 if you were comparing apples to apples,” Parkinson said.

“In my opinion, we’re going to get the crops finished. It’s been cool here the last few weeks, but that’s really kind of saved us. The crop has really hung in there very well.

“But we do need to catch up on GDUs, and we will start to catch up this week. It looks like we’re going to average 25 growing degree units a day for the next 10 to 14 days, which is going to catch us up pretty quick.

“It will be interesting how the crop holds in there. We’re all well below normal on rainfall right now, so we could all use a pretty good rain any time.”

At this stage in the growing season, corn growers need to look at several agronomic and harvest issues.

“We need to look at the agronomics of the plant, look at the health ratings and look at these fields that maybe are poorly drained,” Parkinson said.

“I think the big caveat is the fields that are poorly drained are the ones you really need to watch because we probably lost a little more nitrogen on those farms and then early root development might have been compromised.

“So those might be the first fields that we really need to watch for stalk breakdown and cannibalization from that stalk if we do not get a rain over the next week or two when this plant needs it during grain-fill.”

Parkinson doesn’t believe disease was a major inhibiting factor this growing season.

“There is disease out here. There is a little more gray leaf spot than I thought,” he said. “When we were starting to tell people to pull the trigger, I was really having a hard time telling guys to spend $30 an acre because things were so clean.

“But at that time we just focused on looking at the agronomics of their plant and if it has a lower stay-green rating and its pretty susceptible to gray leaf spot, if you’re going to spend the money spend it on those first.

“We had a lot of dewy mornings and the gray leaf really did kick up, but I still don’t think it’s going to be a real big problem.”

The top issue in this year’s corn is the plant’s ability to uptake nitrogen after it turned dry. Parkinson also has not seen any major insect problems this year in his district.

“There are some rootworm beetles flying around. Japanese beetles are hanging around longer. Usually you’d think six to eight week with those, but they’re still hanging around,” he said. “Right now at this point I’m not really worried about any insects.

“When we were starting to pull the trigger on fungicide, there was kind of a hotbed over Knox County by that Yates City area where there seemed to be a lot of Japanese beetles feeding.

“They were attracted to the first fields to pollinate and there were few fields over there that really got clipped and it’s going to hurt the yield in a small percentage of fields.”

In looking at fields the first week of August, Parkinson said, “I really thought we could have a lot of 240, 250 out here and I still think there is some of that potential, but if we don’t get rain in the next week to two weeks it’s really going to drop down to more of an average crop.

“Drainage is so key, and those fields that are well-drained where water didn’t pond too long just really look consistent and are not firing up, but those poorly drained farms are starting to fire up.”

Farmers in Knox and Peoria counties had two windows for corn planting this year — April 29 to May 1 and after May 14.

“All along I thought that early-planted corn had an advantage, it handled the water better, it all looked better,” Parkinson said.

“But as we look at fields over the last couple of weeks, that early-planted corn is about 150 GDUs above the mid-May planting. So it does have its advantage of being farther along, but it’s showing more tip-back, and we’re not getting quite as good of a kernel count on that first crop planted as we are on the mid-May planting.

“I think part of it is, when you think about the May 15 planting, that stuff all pollinated when it was really cool and in perfect conditions, and that May 1 pollinated during that early heat wave we had.

“That might have affected it a little bit. That May 15 planting pollinated in the most beautiful weather.

“Kernel counts are still tremendous. I think we have a good crop, but when I look at yields, I’m looking at 160 to 260 right now and everything in the middle.”

Parkinson also estimated when harvest could be expected.

“I did an estimate on black layer, and on an average 110-, 111-day hybrid planted May 1 I’m think it should black layer around that Sept. 13 or 14, depending on the heat units from here on out,” he said.

“Then you add another 10days on it to get it from 31 percent (moisture) to 25 percent. I think there will definitely be some corn picked the last week of September, and the majority of it will be picked in the first week of October.”