Farm Progress

Winfield United agronomists offer detailed look at corn and soybean issues as of August 17, 2017.

August 19, 2017

13 Min Read

In this fourth installation, Winfield United agronomists offer details on corn and soybeans as they head into grain fill stages. Concerns highlighted include nitrogen deficiency, crop variability, dry conditions and large rain events cutting yield, cooler evenings helping grain fill, various insects and diseases causing issues, potential weed issues with early harvest, and much more.

The agronomists believe yields will be challenged, especially when one considers that 40% of Iowa is in a moderate or severe drought.

Current scouting is still needed, possibly driving need for fungicide or insecticide applications in soybeans. Other tips:

  • Watch weed growth for potential fall burndown application.

  • Weedy fields should be harvested last to reduce the spread of any weed seed.

  • Evaluate stalk integrity and identify fields that may be candidates for early harvest. Farmers shouldn’t base their harvest schedule only on grain moisture.

  • Document any weed, disease or pest problems that were an issue this year. Keep good written scouting records so that information is fresh when you begin planning for next year

Illinois – reported August 14

Crop conditions remain variable across Illinois as crops transition from pollination to grain fill stages. Winfield United agronomist Jason Haegele reports localized areas of dry weather in southern Illinois that may limit yield potential. In contrast, areas in the northern part of the state could have excellent yield, while some areas may have been affected by heavy rainfall in recent weeks. Recent cooler nighttime temperatures and a reprieve from daytime heat will likely benefit the grain-filling process across the state.

On average, most corn is at the R4, or dough, stage across the state. Depending on the planting date and the amount of stress that has occurred, some fields may already be reaching the dent stage. Soybeans have set pods and are beginning pod fill in most areas. The USDA reports that 62 percent of corn and 63 percent of soybeans in the state are in good to excellent condition as of mid-August.

Haegele says Japanese beetles continue to feed on soybean foliage in some areas. In corn, spider mites and aphids may be a concern in localized geographies. He says gray leaf spot and rust can be found in fields, although disease pressure isn’t at thresholds that would limit yield in the fields he’s observed. At this point in the season, the opportunity to benefit from a fungicide or insecticide application in corn is limited. For soybeans, there is still considerable yield to be made through the pod fill period. Haegele recommends taking time to scout soybean fields to identify pests that could still be managed with a fungicide or insecticide treatment.

As September approaches, farmers may start to think ahead to harvest. In areas where warm, dry conditions have prevailed, there is potential for an early harvest. As a result, conditions could favor early establishment of winter annual weeds such as marestail. Haegele says farmers should consider a fall burndown application as a way to stay ahead of weed populations.


Indiana – reported August 14
Indiana crops have shown signs of improvement over the past several weeks, due in part to favorable weather for pollination and the start of grain fill. George Watters, agronomist for Winfield United, says most corn is ranging from the blister to dent stage and soybeans are between R3 and R5.

A wet start to the season left pockets of stunted, uneven crops and blank holes in some fields, but Watters says recent weather should promote ample kernel fill. The latest state yield forecasts are predicting an average 173 bushels per acre for corn and 55 bushels per acre for soybeans. The USDA reports that 55 percent of corn and 56 percent of soybeans are in good to excellent condition in Indiana as of mid-August.

Nitrogen deficiency is starting to aggressively appear in sandy and waterlogged fields where amendments were not made. Watters says this will most likely affect stalk health, and fields will need to be monitored for standability as harvest approaches. Late-germinating and escaped weeds are also appearing. It’s not uncommon to see marestail, ragweed and pigweed species in Indiana fields as harvest approaches.


Foliar diseases in corn and soybeans have been identified in localized areas. Rust has been the predominant disease so far in corn.  Gray leaf spot and northern corn leaf blight were slow to develop this year, but are spreading faster now as the season progresses, Watters says. Septoria and frogeye leaf spot are the primary soybean diseases this year. Sudden death syndrome in soybeans is also starting to show up and will continue to worsen if rainfall continues. Pod-feeding insects including stinkbugs, which are reaching threshold levels in some areas, are also a threat to soybean yield.

Watters recommends that farmers continue scouting fields as September approaches to evaluate stalk integrity and identify fields that may be candidates for early harvest. He says now is the time to document any weed, disease or pest problems that were an issue this year to help shape plans for next season.

Iowa – reported August 14
Depending on where you are in Iowa, crop conditions are highly variable. Ryan Wolf, WinField United agronomy manager, says fields look great in areas where there has been consistent moisture throughout the growing season. But you don’t have to look far to find crops that have received less rain and are showing signs of stress. The latest U.S. drought monitor reports estimate that 40 percent of the state is in a moderate or severe drought.

Wolf reports that corn in Iowa is at the blister or early milk stage, while soybeans are at R3 or R4. On average, he predicts that recent cool weather may put the state slightly behind on growing degree unit accumulation for this time of year. The latest USDA report indicates that 61 percent of corn and 56 percent of soybean crops are in good or excellent condition in the state.

Insect pests are threatening crops in some parts of Iowa. Wolf says in the northwest part of the state, 40 to 50 soybean aphids per plant are being documented in pocketed areas. He reminds growers that soybean aphid populations multiply quickly, so it’s important to keep an eye on fields. Western corn rootworm populations are also of concern, especially in fields where single-stack or conventional corn is planted.

Wolf encourages growers to stay diligent with scouting because problems you see this year are likely to come up again next year. He recommends keeping good written scouting records so that information is fresh when you begin planning for next year.

Michigan – reported August 15
On the whole, corn and soybean crops are looking good, though there are some areas in the state that are struggling because of lack of rainfall, says Jason Roth, agronomist with WinField United. Thunderstorms have been hit or miss, so a number of farmers were fortunate to catch some rain for a healthy crop while others could benefit from additional moisture. Most corn is currently between the R2 and R3 growth stages, while the majority of soybeans are in the R3 to R4 pod stage, or early R5 seed stage.

Some farmers have been dealing with western bean cutworm in their cornfields. Many applied an insecticide to combat these pests a few weeks ago and included a fungicide in the tank with that application. There still might be some western bean cutworm in fields, however, so farmers should continue to be on the lookout and evaluate any potential damage, although the time to address cutworms has passed, Roth notes. At the present time disease pressure has not been too high, especially in drier areas.

Bean leaf beetle or stink bugs are causing battles in some soybeans fields. These pests can damage pods and cause yield loss, so it is important to watch for them. Japanese beetle has also been spotted in soybean fields. If needed, insecticides or fungicides can be valuable when applied to soybean plants during the R3 to R4 growth stages. This is also a good opportunity to apply a micronutrient such as manganese, says Roth. Manganese is particularly effective at the R4 stage and return is high if it is applied, he adds.

Going into September, farmers should be mindful of harvest order, moisture levels and stalk integrity. They should make sure corn stalks are solid and able to withstand any high winds that could cause them to flatten before harvest. When determining harvest order, farmers shouldn’t base their schedule only on the amount of grain moisture.


Weedy fields should be harvested last to reduce the spread of any weed seed. This is especially important for fields with waterhemp; in fact, Michigan is seeing some results of waterhemp weed seed spread from last season. 

Minnesota – reported August 10
Corn is in the R2 growth stage with fields moving into R3, says Joel Johanningmeier, ag technology specialist for WinField United. Pollination is complete and kernel development is progressing and moving into the dough stage. Soybeans are moving through the late R3 growth stage and into R4, with full pod set all the way up the plant.

Corn looks good in Johanningmeier’s area of southeast Minnesota, given that corn crops were all planted in a relatively short period of time. Moderate temperatures and adequate moisture made for ideal conditions during the pollination stage for corn plants.

As for soybeans, August precipitation and plant-available water are keys to success, which has been the case. Some areas were affected by excessive rainfall in mid-July, but that has recently stabilized, says Johanningmeier. Soybean crops have a good, healthy look in color, and he anticipates plants will fill the pods they’ve set.


Johanningmeier saw anthracnose in some cornfields earlier in the season, and some of it was treated early with a fungicide. Farmers also applied late-season fungicide to help protect corn crops — particularly hybrids that have high responses to fungicide applications. Response-to-fungicide scores for specific hybrids are identified through the Answer Plot Program, and many agronomists and farmers have used this data to help determine if a fungicide application will pay off this year.

The soybean aphid population has been low throughout the area, with insects appearing a little later than normal, he says. There has been some spraying for aphids in western Minnesota, so there are pockets; but overall, populations have been low.

There is some white mold in soybeans in the far southeast corner of Minnesota, which is an issue every year; however, compared to past years, the incidence is quite low. According to Johanningmeier, because it is late in the season, the possible impact on yield is moderated.

Moving toward fall, farmers should address issues such as lodging or diseases, and note how quickly crops are drying down. In-season imagery can help farmers identify the size and scope of issues in the field and use that information to plan appropriate harvest schedules. Farmers should also talk with their agronomists about nutrient management. Now is a good time to evaluate how their nutrient management programs went this year and how they can apply learnings in 2018. Johanningmeier says he is seeing some positive differences this year for farmers who continue to manage nutrients.

Ohio – reported August 9
Corn growth stages range from VT to R3, while soybeans are anywhere between R2 and R4, says Joe Rickard, WinField United agronomist. The look of corn and soybean fields varies widely between areas, with some fields looking good and others in poor shape. Many areas of Ohio have had huge amounts of rain this growing season, and this has taken a toll on a number of fields, with corn and soybean plants looking drowned out and a number of fields with greatly reduced populations.

Japanese beetles are a problem in both corn and soybean crops this year. As far as diseases, gray leaf spot and northern corn leaf blight have appeared in corn crops. Frogeye leaf spot, brown stem root rot and Phytophthora root rot are just some of the diseases that Rickard has found in soybeans.

 Some growers are on the fence about whether or not to apply fungicide on both their corn and soybean fields. It’s important to remember that fungicide applications mixed with needed nutrients will help protect yield. Hopefully, farmers will have a late-season tissue sample to inform them about what nutrients they may need to put in the tank along with the fungicide.

As crops begin to dry down and harvest approaches, farmers need to keep an eye on which fields they may need to harvest first, Rickard notes. Prioritization of fields will be key, especially if fall brings more wet weather to the state.

South Dakota – reported August 14

The first week of August brought much-needed scattered rain and cooler temperatures to parts of South Dakota, but the effects of a dry summer are still evident. Ryan Wolf, WinField United agronomy manager, says he expects to see below-average yields in some areas due to the extended period of heat and drought. Wolf estimates soybeans across the state to be at the R3 or R4 growth stage, and corn at the early milk stage.

USDA crop condition reports confirm what farmers are seeing across the state. A majority of the corn and soybeans in South Dakota are in fair to very poor condition. Only 34 percent of corn and soybean crops are listed in good or excellent condition based on the August 14 report. The tough conditions are pushing some farmers to chop heavily stressed fields for silage instead of waiting to harvest grain.

Insects are one of the main concerns for farmers right now. Across the I-29 corridor, western corn rootworm has been an issue, especially where single stack or conventional corn is planted. Spider mite populations in corn and soybeans are also on the rise in drier areas. Wolf recommends tank mixing multiple modes of action when applying insecticides, as some pyrethroid resistance has been documented in soybean aphid populations in North Dakota and Minnesota.

Farmers should continue scouting and documenting late-season pests to help develop plans for next year. Wolf also advises farmers to keep an eye on late-season plant health to target fields where a timely harvest may be necessary due to extra stress.

Wisconsin – reported August 16
Both corn and soybeans in Wisconsin are seven to 10 days behind normal, says Tim Mares, senior agronomy advisor with WinField United. Some corn has just tasseled, while other corn is well into the milk stage. Soybeans are currently closer to R3 or R4. Crop growth is behind schedule because of a wet spring, late planting and cold soil temperatures. Despite these circumstances, crops are still in very good condition. If Wisconsin gets more rain and heat, Mares says, the state can look forward to a good crop.

In terms of late-season challenges, Japanese beetles are still present in soybeans, along with some aphids. The warm weather is also conducive to white mold pressure in soybeans. Mares hasn’t seen many insects in corn, but rust and anthracnose are the current pressures. Some corn is also showing symptoms of nitrogen deficiency.

As September approaches, farmers should begin to shift their focus to fall preparation. If Wisconsin experiences a large crop, Mares recommends a fall fertilization. Fertilizer is generally less expensive than last year, so farmers should take this into consideration. In addition to fertilizer, farmers are also thinking ahead to nutrient applications. It’s crucial to replace the nutrients that the past crop removed, so applying potash, phosphorus and other nutrients based on each field’s need is a must.

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