More Than 90% of State in Drought as Harvest Nears

As harvest nears, University of Missouri Extension agronomy specialists see signs of flash drought creeping into Missouri farmland and threatening crop yields.

According to MU Extension state climatologist Zachary Leasor, the U.S. Drought Monitor map for Missouri released on Sept. 4 shows that 93.68% of Missouri is at least abnormally dry following an unusually wet spring.

The southeastern and southwestern parts of Missouri are hardest hit, but the rest of the state except for northwestern Missouri is showing emerging signs of drought.

Soybean specialist: Anticipate harvest

The rain shortfall comes just as most soybean are in the seed-filling stage, when demand for water is highest to produce and transfer photoassimilates into seed reserves, says MU Extension state soybean farming systems specialist Andre Froes de Borja Reis.

“Under dry conditions, soybean seeds may become undersized, resulting in yield loss,” Reis says.

He recommends that growers consider anticipating harvest. “Drought has already reduced seed formation in some regions and planting date scenarios, and any rainfall on harvest-matured beans could trigger seed deterioration and price penalties,” he says.

Undersized and overdried beans are particularly vulnerable to deterioration if rainfall there’s rain after harvest maturity. Beans with low moisture content become especially prone to damage following rainfall, says Reis.

Low test weights are already expected due to drought during the seed filling, as predicted by the University of Missouri’s Soybean Growth and Yield Tool.

Something similar happened in the 2024 growing season when Hurricane Helene brought heavy rainfall to southern Missouri in late September, exposing mature beans to excessive moisture.

However, seed deterioration and other quality issues only became apparent after the storm. Deteriorated seed from the 2024 storm was tested and found to contain species of Fusarium, Cercospora and Diaporthe, which can lead to dockage at the elevator, says Mandy Bish, MU Extension state plant pathologist. Learn more from the MU Integrated Pest Management article “Soybean Seed Deterioration in Southern Missouri.”

Reis notes that the Soybean Farming Systems Yield Prediction Tool currently forecasts a yield decrease in several areas. More details are available at MU Extension Soybean Growth Monitoring.

Weed scientist: Watch for herbicide carryover

MU Extension weed scientist Kevin Bradley says growers should watch for herbicide carryover to cover crops that will be seeded or planted soon. Residual herbicides applied later than usual in corn or soybean this year may not have fully degraded because of dry conditions at the end of the season. This creates the potential for injury of cover crops species planted in the coming weeks, says Bradley.

Disease and drought

“With rapid corn senescence and drought conditions, farmers should scout for stalk and ear rots, as some fungal pathogens favor these stresses,” says Bish.

 The “push test” is a simple way to assess lodging risk: Push 20 plants in five areas of a field about 45 degrees. A weak stalk will snap or break, while a strong one will remain intact.

Bish advises prioritizing early harvest for fields where more than 10%-15% of stalks are weak or where noticeable ear rot is present, as many ear rot fungi continue to grow until grain moisture falls below 15%.

Find more information in “An Overview of Ear Rots” from the Crop Protection Network.

No immediate relief in sight

Leasor says no significant rainfall is forecast, and tropical storm relief like last year is unlikely.

Preliminary data for August 2025 indicated this was Missouri’s second-driest August on record, with just 0.79 inches of statewide average precipitation. Springfield saw its driest August ever with only 0.19 inches, and Columbia recorded 0.11 inches, its second driest.

“This is a classic flash drought, developing rapidly after a wet growing season,” Leasor says.

Since the 1980s, Missouri has experienced 16 drought disasters costing $1 billion or more each in damages, underscoring the need for proactive management, he says.

 

Free Soybean Cyst Nematode Tests for Missouri Farmers

University of Missouri Extension, SCN Diagnostics and Missouri Soybean Merchandising Council are again offering free testing for soybean cyst nematode (SCN), the No. 1 pathogen of soybean in the United States.

Mandy Bish, MU Extension plant pathologist and director of the SCN Diagnostics clinic, says Missouri farmers can submit four soil samples for free SCN egg counts to the clinic in Columbia. Additional tests are available for a nominal fee. Soybean infected with SCN often appear healthy above the ground, making the pathogen difficult to detect, says Bish.

SCN is a microscopic pest that damages soybean roots and reduces the plant’s ability to take up water and nutrients, leading to stunted growth, poor pod development and significant yield loss.

A higher percentage of Missouri soybean fields have detectable levels of SCN compared to a decade ago, and those fields also have higher population densities, according to 2024 research by MU doctoral student and senior research specialist Jeff Barizon, who is currently in the second year of a statewide survey to identify parasitic nematodes in Missouri soybean fields.

Fall, near or shortly after harvest, is the preferred time to test, says Bish.

She recommends sampling of fields that have never been tested or were tested more than five years ago.

Sampling for SCN is a little different than sampling for other purposes, says Bish. Recommended soil cores are 1 inch in diameter by 8 inches deep and taken in a zigzag pattern. Divide fields into sections of 10-20 acres using natural boundaries such as different topographies, areas where sudden death syndrome or SCN symptoms appeared previously and low-yielding areas of the field.

Nematodes to not appear uniformly in fields, so it is important to take samples using recommended methods.

Download the sample submission form and learn more about the sampling and submission process at https://scndiagnostics.com.

Contact the laboratory at 573-884-9118 or scndiagnostics@missouri.edu. You can also contact Bish at bishm@missouri.edu or 573-882-9878.

SCN Diagnostics is a partnership with the University of Missouri and MU’s College of Agriculture, Food and Natural Resources.

 

Soybean Tentiform Leafminer Found in Missouri

University of Missouri Extension state crops entomologist Ivair Valmorbida has confirmed the presence of a new soybean pest in Missouri.

Valmorbida confirmed soybean tentiform leafminer in central Missouri soybean fields in the first week of August. MU Extension agronomist Todd Lorenz was present in the field when the pest was found. MU Extension specialists found in the insect in only one of more than 70 fields sampled so far, but its presence is concerning, says Valmorbida.

Soybean tentiform leafminer was detected feeding on soybean in Minnesota and the Dakotas in 2021 and Nebraska in 2024.

According to the University of Minnesota, it feeds on two native plants, American hogpeanut and slick fuzzybean, both of the Fabaceae family, the same family as soybean, says Valmorbida.

This pest is a small white larva that turns pale green as it matures. The adult moths are less than ¼ inch long and have orange and white wings with gray-black marks.

Adults lay eggs on the underside of soybean leaves. Larvae feed inside the leaves and tunnel to create mines that do not cross the midribs or main lateral veins of the leaves. The mined tissue eventually dies, resulting in less leaf area, similar to defoliation.

On the underside of the leaves, mines enlarge from small, linear ones to become larger, elongated, oval white blotches. These mines become tentiform – slightly raised, or tented – on the upper side of the leaves. Soybean tentiform leafminer appears primarily along field edges and in forested areas.

There are no well-established management practices for this insect, but University of Minnesota researchers report that several parasitic wasps, natural enemies of the leafminer, and translaminar insecticides could provide control.

Valmorbida encourages farmers to scout soybean fields and to contact their local MU Extension agronomist if they suspect the presence of tentiform leafminer. Farmers may also reach Valmorbida at 573-882-6446 or ivairvalmorbida@missouri.edu.

Valmorbida is working with other universities to determine the distribution of tentiform leafminer in soybean fields. For more information, see the University of Minnesota publication “Soybean Tentiform Leafminer in Minnesota Soybean” at https://extension.umn.edu. You can also follow updates on tentiform leafminer and other pests at CropWatch, a resource provided by University of Nebraska–Lincoln at https://cropwatch.unl.edu.

 

Location, timing critical for double-crop success

Double-cropping soybeans after wheat provides the opportunity to harvest two crops in the same year from the same piece of land. But here are challenges and concerns with double-cropping, and a University of Missouri Extension agronomist says location is a big factor.

 

“In the middle part of Missouri we’re going to be planting soybeans around July 1, but is there enough time for the soybeans to mature before the first frost?” said Bill Wiebold. “In this part of the state, probably, but as you go farther north the growing season shortens just enough that by the time you get to the Iowa border it probably doesn’t pay to double-crop.”

 

Conversely, as you move farther south in Missouri double-cropping becomes more likely to succeed. Wiebold says that in the southeastern part of Missouri where quite a bit of wheat is grown, almost every acre is double-cropped with soybeans.

 

Double-crop soybeans don’t typically yield as high as full-season beans, but with recent high soybean prices it can still be very profitable. However, if you lose too much yield on the soybean side, you have to make it up on the wheat side. Wiebold says that can be difficult because wheat prices haven’t followed the same trend soybeans have taken.

 

“It’s a complex equation between what happens to the wheat and what happens to the soybeans,” Wiebold said. “What are the different prices? What kind of yields can you get? So it’s a little complicated and it becomes even more difficult north of Highway 36.”

 

Aside from the length of the growing season, there are other considerations when double-cropping, such as straw management.

 

“The wheat is going to produce straw. You can bale it, and that’s another source of revenue if you have a place to sell that straw,” Wiebold said. “You have to be careful, though. If you wait a couple days to plant, that could hurt your bean yield. So you have to calculate that into the equation.”

 

Another challenge is that double-crop beans are planted at such a time that seed filling will occur in late August, when the day length is shorter and the angle of the sun is greater, so there is less sunlight and less yield potential.

 

“You also get a shorter seed-filling period,” Wiebold said. “It may be 35 days versus 55 days for full-season.”

 

Moisture is also a crucial factor when it comes to double-cropping.

 

“The length of growing season is about location,” Wiebold said. “But wherever you double-crop, wheat has taken quite a bit of moisture out of the soil. So what is that weather going to be—not only the day that I plant but also the next six or seven days as I’m trying to get those soybean seedlings out of the soil? Quite often it is just too dry and the beans don’t emerge or they emerge spotty.”

 

Wiebold says some practices that can make double-cropping successful include having a high-yielding, early-maturing wheat variety, no-till planting, planting as early as possible, using narrow rows, and increasing seed density.

 

“No-tillage is a good water-conservation practice and it’s a good time-conservation practice,” he said. “Narrow rows are important because that canopy forms more quickly, capturing sunlight sooner and helping yield.”

 

Wiebold recommends selecting a soybean variety that you would use in a full season, so it is tall enough and produces enough leaves to drive the yield. He also says a higher seed density is needed when double-cropping.

 

“If we have 100,000 to 110,000 plants per acre, that captures most of the yield in full-season situations,” Wiebold said. “But you may need 140,000 or 150,000 plants in a double-crop situation. The plants are shorter; they don’t produce as many nodes, so you have to add some plants to make up for those nodes.”

 

For more information, contact your local MU Extension center.

First Corn and Now Soybean Variety Tests are Available at Local Extension Offices

The results of the soybean performance trials are now available at your local Extension office.  Soybean yields were also impact by drought.  The Craig site caught some rain with the highest yielding variety coming in at 58 bushels per acre. The lowest yield was 31 bushels.  Those results are the Group 3 soybean maturity group. The group 4 maturity group ranged from a high of 66 bushels to a low of 49 bushels.

Another soybean variety test is conducted at Albany.  Group 3 soybeans ranged from a high of 44 bushels to a low of 26 bushels. The group 4 had a range from 48 bushels to 34 bushels.

 

The test results are in a booklet form and contain 125 pages of information of the testing sites across Missouri. In the back section of the booklet are the maturity rating, seed treatments, resistance to phytophthora, SCN source, SDS rating,  herbicide resistance traits, and list of seed suppliers.

 

For more information, contact Wayne Flanary at 660-446-3724 or Heather Benedict at 660-425-6434, Regional Agronomists, University of Missouri Extension.

Shattering Soybeans Reported

Stress conditions this summer are showing up in soybeans as those stressed areas in fields are shattering. Pods are breaking open releasing seeds to fall on the soil. Those fields that handled the stress significantly well are not shattering.

 

It is important to scout your fields and determine your plan of action. Most fields have green soybeans mixed with shattering soybeans so the decision is not easy.  Do you wait or take some discount.

 

Four to five soybeans per square foot spread uniformly across a field equal a bushel per acre loss.  I would use four with seed size under 3,200 seeds per pound variety and five with seed size greater than 3,200 seeds per pound. Sample several areas of the field and determine how much loss you are having.

 

I was in fields near Plattsburg last week which were severely drought stressed and there was considerable yield loss. Reports of other fields showing losses are coming into the Extension office again where the plants were drought damaged.

 

For more information, contact Wayne Flanary at 660-446-3724 or Heather Benedict at 660-425-6434, Regional Agronomists, University of Missouri Extension.

Be Informed Before Using Soybeans for Forage

Many Missouri producers are asking if it is safe to use soybeans for livestock forage. The topic was brought up repeatedly by attendees at the Missouri State Fair in Sedalia.
Tim J. Evans, toxicology specialist at the University of Missouri College of Veterinary Medicine, answered inquiries on the subject by researching the chemical mechanism of action of a commonly used herbicide, Cobra.
“Current drought conditions have caused farmers to consider grazing, baling or ensiling soybeans for livestock consumption,” said Evans. “As is routine, much of the soybean crop has been sprayed with herbicides, especially Cobra, which contains lactofen and petroleum distillates. It is important that farmers be aware of what is known and what is unknown about this product before letting animals consume soybean plants to which this product has been applied.”
Lactofen is classified as a diphenyl ether (nitrophenyl ether) contact herbicide, which acts by destroying plant cell membranes. Lactofen is considered slightly toxic following ingestion and has been associated with liver disease and other abnormalities in rodents following chronic exposure to relatively high doses. Naphthalene and other compounds in Cobra can also be associated with animal illness.
“With the information currently available, and apparently without specific testing for the safety of feeding Cobra-treated soybeans to animals, the manufacturer must include information on the label pertaining to the consumption by livestock of treated crops,” said Evans. “The label states that animals should not be allowed to graze on previously treated green forage or stubble. It states that treated soybean silage (ensiled soybeans), as well as treated hay and straw, should not be fed to cattle.”
Evans emphasized that the label also clearly states that hay or straw from treated plants should not be used for animal bedding.
Farmers, livestock producers and veterinarians are encouraged to be familiar with the manufacturer’s label instructions and livestock withdrawal times, as well as the material safety data (MSDS) sheets, for Cobra and all other commonly used, commercially available herbicides. It should also be noted that some herbicides can enhance some plants’ palatability and ability to accumulate nitrate.
Producers can read about the effects of other herbicides and pesticides on crops that may eventually be used as animal feed on the MU Integrated Pest & Crop Management website at ipm.missouri.edu/IPCM/index.cfm?ID=388.

Corn and Soybean Condition

Corn lodging is occurring in drought stressed areas of corn fields. Growers should keep a close eye on their fields and consider early harvest. Check fields by pushing corn over and determine if there is high risk. Often, when corn plants are drought stressed, that the lower part of the plant may be cannibalized to fill the ear which leads to lodging.
There are many differences in corn yields across northwest Missouri. There are scattered rain events that helped corn yields whereas others missed rains and there is little grain on the ear.
As we move into seed fill with our soybean crop, most fields have a limited amount of pod set. Dry conditions caused many flowers and pods to abort. Next, if dry conditions continue, seeds in the pods will abort. The soybean plant will respond to its environment by only filling what seeds it feels it can produce.
For more information, contact Wayne Flanary at 660-446-3724 or Heather Benedict at 660-425-6434, Regional Agronomists, University of Missouri Extension.

Lush green soybean field may not be good sign

Farmers are reporting that in spite of prolonged drought and hot temperatures their soybean plants appear amazingly green for this time of year.
“Green soybean plants may not be a good sign,” says a University of Missouri Extension soybean specialist, “even though the plants appear to be thriving, compared to the brown and dead corn stalks in adjoining fields.
“They may have adequate moisture,” says Bill Wiebold, of the MU plant science division. “More likely, the green results from high nitrogen levels in leaves that have not converted into protein stored in seed pods.”
The plant requires a steady flow of water moving up the plant system from roots to leaves to pods, Wiebold explained in an MU teleconference.
“When there is no water, the system stops working. That has happened in many soybean fields.”
The bright green color may actually mean there will be fewer soybean seeds in the pods.
Without pods, there is no place for the plant to store the amino acid created by photosynthesis, Wiebold said. Usually, by this time of year, the protein is stored in the seeds. Then, the plants begin to fade.
“There may not be a very large fruit load on those green plants.”
Late rains may allow pod fill to resume. However, prolonged drought may have caused soybean blossoms to abort. The result may be no pods for the seeds.
”The soybean plant seems to never stop producing new branches,” Wiebold said. “If there is an open space the soybean creates a new branch to fill the void.”
The node at the base of each new branch contains three new buds for new branches or new blossoms to appear.
That drive to reproduce makes it very difficult to predict potential yield in a soybean field. That is unlike the corn plant, which makes one attempt at reproduction and quits.
“The corn plant has what we call a determinate development,” Wiebold said. “The soybean plant, by contrast is indeterminate. It just keeps trying.”
Rainfall will determine if there is still yield potential.
“It is very rare for a drought to start as early as it did this year,” Wiebold said. “We just have not experienced anything quite like this before.”
“The uncertainty on yield makes it more difficult to decide whether to harvest soybean plants for livestock forage; or, to wait and see if pods develop and seed grows before harvest.”

Drought Damaged Soybeans Can Make Cattle Feed

Soybeans that won't make a seed crop offer potential high-quality forage for beef and dairy producers. The decision to cut beans for hay won't be easy, say University of Missouri Extension specialists. "It will be difficult to tell when there is no potential for a seed crop," said Bill Wiebold, MU soybean specialist. "Waiting too late to cut soybeans for forage decreases feeding quality," said Justin Sexten MU beef nutritionist.
Joe Horner, MU Extension economist, developed a spread sheet for producers to put in their own numbers to figure value for forage. Horner said the cut off for the transition from beans to forage is when yield drops below 10 bushels of soybeans per acre; and if forage provides one ton or more of quality dry matter per acre. There is potential for tons of needed forage, Horner adds. The Missouri crop condition report showed 3.7 million acres of the 5.3 million acres of soybeans planted this year rated poor or very poor as of July 29.
The first step on the way to hay, Horner said, is a visit with the crop insurance adjuster. "Don't' cut anything, without checking crop coverage." Rob Kallenbach, MU forage specialist, said soybeans now have the potential for a feeding value equal to full-bloom alfalfa hay. Currently that hay sells for $200 per ton. High quality alfalfa brings $300. Wiebold said judging potential for soybean yield will be more difficult than for corn. "Corn makes one attempt at making an ear and that is over in a few days. The soybean keeps setting blossoms for 30 to 40 days, trying to make pods. A late rain can increase bean yields. "A lot depends on who owns the soybean field and if they need forage," Wiebold said.
All the specialists caution producers to read the label on any pesticide used on the soybean crop during the growing season. The most widely used soybean herbicide is glyphosate (RoundUp). It has a 14-day-waiting period before harvest for forage. However, most herbicides require much longer periods between application and harvesting of soybeans for forage. In his spreadsheet example posted on the MU AgEBB website, Horner used a value of $16 per bushel for soybeans. And a value of $164 per dry matter ton of forage. Justin Sexten said timing for cutting soybean plants for forage will be critical. Leaves on the mature and dried soybean plant shatter and fall quickly. Nothing but stems is left after maturity.
Wiebold said transition from what looks like a good crop and a dead crop can be just a few days. The MU specialists agree on one thing. Making soybean hay isn't easy. The favored way to harvest soybean plants is as high-moisture hay, wrapped in plastic. Balage makes high quality forage with less leaf loss. After using the new soybean spreadsheet, Kallenbach said there are some clear breaks. A yield above 10 bushels per acre favors harvest of soybeans. However, yields below five bushel per acre clearly show more value as forage. "Other factors can change the decision between five and 10 bushels per acre. That won't be an easy decision."
Wiebold said, "Once you make a decision to cut soybean for forage, or to harvest beans, do not look back. There's a good chance you will think you made a wrong decision, either way." In a drought teleconference call, Bradley, the weed specialist, had the last word. "Read the label, before harvesting soybeans for forage." Horner's soybean spreadsheet can be found listed under "Silage" at http://www.agebb.missouri.edu/dairy/feed/

Watch For Two-Spotted Spider Mites Damaging Soybeans

Spider mites are a common pest during dry conditions. This pest prefers dry dusty conditions.  Under a severe drought, mite populations can double every 5 to 7 days.  Rains can cause the mite populations to decline but fields should continue to be scouted.

Spider mites are first found along field borders or waterways.  Mite damage first appears as speckling or spots on the soybean foliage. Later injured leaves turn yellow then brown and die.  Damage moves across the field as mites infest additional soybean plants. 

You may need a hand lens to see mites.  Also, a white sheet of paper to shake the mites on will help you see them.  The mites once shaken on the paper will crawl about.

Generally, spider mites occur later in season.  However with the dry conditions, damage can be found on small soybeans.  A general recommendation is to control this pest when the foliage yellowing reaches 20% before pod set and when foliage turns 10% after pod set.

Heavy infestations of this pest can cause severe damage.  In my experience in the 80’s, spider mites would begin as a small circle in the field.  Then the wind would catch them and move them across the field.  There would be small circles of damage from the pest, and then the circles would enlarge causing damage.  It is important to note that the yellowed areas are already damaged and the pests are moved onto undamaged plants to feed.

Scouting is critical.  Since wind picks up this pest, one should watch the entire field.  Plants may show damage symptoms for up to 7 to 10 days following control of spider mites.

Dr. Bailey reports spider mites found along the Iowa and Missouri borders.  At the time of printing of this news article, I have not had any local reports into the Extension office.  With dry weather, however, it is a matter of time before we have this problem.

For more information, contact Wayne Flanary at 660-446-3724 or Heather Benedict at 660-425-6434, Regional Agronomists, University of Missouri Extension.

You should still scout for soybean seedling diseases

With above-average temperatures and ideal planting conditions this spring in most of Missouri, widespread soybean seedling diseases are less likely to occur, but farmers should still be on the lookout, says a University of Missouri Extension agronomy specialist.

 

“Soybean seedling diseases can and do occur every year in Missouri,” said Travis Harper. Areas of fields that stay wet or are compacted are particularly at risk.

 

“Once any of these diseases are found in a field, there is little that can be done to control the disease,” Harper said. “However, it is still important to scout seedlings for the presence of these diseases so that precautions may be taken to avoid plant death or yield loss next year.”

 

Here are some of the most common seedling diseases of soybeans:

 

Pythium seed decay and damping-off – Pythium is the most common fungus causing damping-off in soybean. It is more likely to occur on soybeans that are planted early in the season in colder soils. Infected plants have a rotted appearance and can easily be pulled from the soil.

 

Phytophthora seedling blight – Phytophthora is a soil-borne fungus that causes seed decay, pre- or post-emergence damping-off and seedling blight of soybeans. It is most common in soybeans planted in warm (greater than 65 degrees) and wet soils. The seedling blight phase may cause yellowing, wilting and death of the plant. It is more likely to occur in low-lying or poorly drained areas.

 

Rhizoctonia seedling blight – Rhizoctonia is another common soil-inhabiting fungus that can cause seed decay and pre-emergence damping-off of soybean seedlings. Symptoms of rhizoctonia are found on seedlings, young plants and even older plants and consist of localized red to reddish-brown lesions near the soil surface. Infected plants may be stunted or less vigorous than healthy plants, causing uneven stands. Severe infestations and dry weather may cause death of the plant. Like phytophthora, rhizoctonia prefers warmer soils.

 

Fusarium seedling blight – Fusarium seedling blight is caused by a soil-inhabiting fungus and causes weak or stunted plants and uneven stands. The disease causes a rot of the root system while the aboveground portion of the plants may start to turn yellow. Plants may eventually wilt and die during periods of warm to hot weather. The disease is most severe when the soil is saturated and soil temperature is around 57 degrees at planting, conditions that are not as common this year.

 

Charcoal rot – Charcoal rot is one of the most common diseases found in soybean. It typically shows up as a mid- to late-season disease on mature soybeans but can also occur early in the season on seedlings. Symptoms include reddish-brown discoloration from the soil stem up that may become dark brown to black as the disease progresses. Plants may die if conditions become hot and dry.

 

“If it is determined that one or more of these seedling diseases are present, options for next year may include using good-quality disease-resistant seed, only planting in ideal seedbed conditions, or using fungicide seed treatments,” Harper said.

Planning for Critical Weed Control

Each year, we are busy managing our crops. Sometimes we delay post-emergence weed control trying to get the most weed control during a spray application. However the cost of delaying weed control costs yield.
There are critical stages in the growth of corn and soybean where weeds do not significant hurt yield before or after these time periods. Critical timing in corn is often at high nitrogen rates, between the 6th and 9th leaf stage of corn. If you are using lower nitrogen rates, then the leaf stage may be lowered so it is from the 4th to 9th leaf stage.
As for soybean, the critical weed stage is the first trifoliate stage in 30-inch rows whereas in 15-inch rows it was the second trifoliate. This implies that weed control should begin earlier in wide rows than narrow rows.
Delaying weed control beyond the start of the identified period for weed control will cost the grower an average of 2 percent yield loss for everyone leaf stage delay in corn and also in soybean according to University Nebraska weed research data.
As you make your spring herbicide plans, don’t forget to apply pre-emergence products to manage glyphosate weed resistance and be sure to apply your post-emergence products at the proper time to prevent yield loss.
For more information, contact Wayne Flanary at 660-446-3724 or Heather Benedict at 660-425-6434, Regional Agronomists, University of Missouri Extension.

Wind and Hail Damage Area Crops

The injury from wind and hail damage hit many parts of northwest Missouri. Wind damage occurred about a month ago that affected northern Atchison, parts of Nodaway and Gentry counties. "Then we had two days of storms that combined straight wind and hail causing some of the worse crop injury that I have seen in my career in the Maryville area," explained Wayne Flanary, Agronomist with University of Missouri Extension.

Hail damage around the area varies in intensity. Crops around Maryville and Nodaway County were heavily damaged along with reports of damage in other counties. The worse hail damage looks as if the corn crop was harvested as the field is brown. Corn stalks are cut and lying on ground along with ears. Soybean stems also cut and lodged. This damage will be a complete loss.

Lighter damaged corn fields have shredded leaves, bruising and lodged corn. Most corn fields were in the dent stage. The starch is hardening causing a milk line. This line moves from the top of the kernel toward the cob. Kernels at this stage will not abort. Kernels may be lighter as the kernel continues to dry down. This is good news where corn fields have standing stalks with ears that can be harvested.

The wind damage from straight line winds broke and bent corn stalks over. In places, it's the whole field whereas others, there are areas within the field. This will be a slow harvest as growers try to pick-up as much lodged corn as possible.

As far as soybeans, the damage occurred during seed fill. The soybean plant takes energy from leaves and other plant parts and places this energy into the seed. Defoliation, broken stems, lodged soybeans all can be found.

Soybean plants will adjust growth for the condition of the individual plant. Four days after the injury, we are seeing brown pods which the soybean plant will abort and they will drop to the ground.

Soybeans will be affected greatly when leaves are lost and stems are bruised and cut. This damaged occurred during the critical seed fill. You can inspect your crops now and check for pod drop. With injury occurring this late in the season, plants will not compensate. They will set as much seed as each individual plant can with the stress placed on it.

The straight wind laid soybeans over in many fields. The shading affect of plants lying on top of each other will reduce yield.

For more information, contact Wayne Flanary at 660-446-3724 or Heather Benedict at 660-425-6434, Regional Agronomists, University of Missouri Extension.

Big Weeds Showing in Soybeans

Some soybean fields have large weeds and these are already out of labeled height with most products. Most post-emergence products work best when weeds are small say 4 to 6 inches tall.

By controlling weeds when small, you are avoiding yield losses by competition from the larger weeds. Smaller weeds are also easier to control.


For those hard to control weeds, you may want to include a tank-mix partner that is specific to that weed species. This will increase control for weeds that may have developed resistance.

Be sure to consider the crop stage when applying when applying weed control products. Injury may occur if applications are to crops outside the labeled height or growth stage. Corn is especially sensitive to late applications compared to soybean.

For more information, contact Wayne Flanary at 660-0446-3724 or Heather Benedict at 660-425-6434, Regional Agronomists, University of Missouri Extension.

Proactive Weed Management

For adequate weed control in soybean, growers need to take a proactive approach using an appropriate pre-emergence herbicide program, said a University of Missouri Extension agronomist.

“Pre-emergence programs have increased in importance within the past several years as the number of glyphosate-resistant weed species has increased,” said Julie Abendroth.

Currently, there are five species confirmed to be glyphosate-resistant in Missouri: common ragweed, giant ragweed, horseweed (marestail), waterhemp and Palmer amaranth.

Glyphosate-resistant waterhemp populations are becoming more common in Missouri, Abendroth said. An MU weed science team conducted a survey in 2008 and 2009 inviting people to submit waterhemp samples suspected to be glyphosate-resistant. Of the 144 waterhemp samples submitted, 58 percent were confirmed glyphosate-resistant. Thirty-nine counties in Missouri are now known to have glyphosate-resistant waterhemp, although the actual number of counties is likely higher.

From 2007 through 2010, MU has investigated the influence of pre-emergence herbicide treatments on waterhemp control. MU plant pathologist Kevin Bradley’s research has shown that there are numerous pre-emerge herbicide options that will provide excellent waterhemp control.

These herbicides all provided excellent control in the three-year study: Valor (2 ozs./acre), Valor XLT (3 ozs./acre), Prefix (2 pints/acre), Boundary (1.5 pints/acre), Gangster (1.8 ozs./acre), Fierce (3 ozs./acre), Enlite (2.8 ozs./acre), Envive (3.5 ozs./acre), and the Authority line of products, which includes Authority First (3.2 ozs./acre), Authority MTZ (10 ozs./acre) and Authority Assist (5 ozs./acre).Other pre-emerge options, including INTRRO, Dual, Outlook and Prowl, were not as effective but did provide some early season waterhemp control. (Mention of trade names within this article does not imply endorsement by the University of Missouri.)

For those growers struggling with giant ragweed control, a proactive approach is very important, Abendroth said.

“It is difficult to achieve adequate control of giant ragweed once plants have emerged, and research data indicates that if ragweed is allowed to compete with the soybean crop for at least four weeks, a 25 percent yield loss can occur,” she said.

From the two-year weed survey, 44 percent of the 27 giant ragweed samples submitted to MU were confirmed glyphosate-resistant.

“In addition to controlling glyphosate-resistant weed populations, the residual control offered from a pre-emerge herbicide will also provide growers with greater flexibility with their postemergence applications,” Abendroth said.

MU Extension’s 2011 Missouri Pest Management Guide (M171) is available for purchase or free download at http://extension.missouri.edu/publications/DisplayPub.aspx?P=M171. The guide provides weed, insect and disease control recommendations for corn, cotton, soybean, grain sorghum, rice and winter wheat.

For more information, contact your local MU Extension center or see extension.missouri.edu.

Fungicide resistance in frogeye leaf spot confirmed

Fungicide applications to soybean have significantly increased over the past five years due to claims of both a reduction in foliar disease and an increase in “plant health.” However, overuse of these fungicides may erode their benefits, warns a University of Missouri Extension agronomy specialist.

Concerns about resistance have centered on fungicides called strobilurons. “Since the development of the ‘strobies,’ plant pathologists have noted the potential for resistance to develop quite easily with repeated use of these chemistries,” said Julie Abendroth.

Because the strobilurons are active only at one specific site in disease pathogens, they possess a high “resistance risk,” she said.

Strobies include products such as Headline and Quadris, as well as combination fungicide products such as Headline AMP, Quilt Xcel, Quadris Xtra and Stratego.

In 2007, Iowa State University specialists identified 23 different plant pathogens resistant to the strobilurons. In October 2010, Carl Bradley from the University of Illinois confirmed the first case of strobiluron resistance in frogeye leaf spot (Cercospora sojina) from a soybean field in Tennessee. In this particular field, strobiluron fungicides were applied twice during the season, but the field continued to have severe frogeye leaf spot. Once analyzed, the samples were shown to require a fungicide concentration 200 to 7,000 times higher than nonresistant frogeye leaf spot samples.

Strobies can reduce the severity of numerous foliar diseases in soybean; however, in on-farm trials in west-central Missouri, a yield response to fungicide application has most often occurred when frogeye leaf spot is moderate to severe, Abendroth said.

“Other foliar diseases do not appear to be as yield-limiting as frogeye leaf spot. It is therefore important that when needed, strobie fungicides remain able to provide control of this disease,” she said.

To prevent resistance to the strobilurons, it is important to make fungicide applications only when needed. If a fungicide application is determined to be necessary, select either a fungicide with a triazole chemistry or a combination fungicide. Triazole fungicides such as Domark, Tilt and Folicur possess a different site and mode of action than the strobie fungicides. Also, the triazoles have a lower overall “resistance risk.”

For more information, contact your local MU Extension office.

(The trade names within this article are given with the understanding that no discrimination is intended and no endorsement by the University of Missouri is implied.)

Soybean rust update

Soybean Rust Scouting Will Continue, but Scaled Down
The University of Missouri Extension staff will scout fields only in the southern part of Missouri. If signs of the disease indicate the pest is moving northward, the next set of Extension agronomists will scout fields in mid-Missouri.
The objective is to detect soybean rust when it first starts to develop in Missouri soybean fields so farmers can be warned about the presence of rust. Once the disease is detected, an all-out alert will be issued to farmers in the area of detection using media. Contact Allen Wrather, Plant Pathologist, Delta Center, wratherj@missouri.edu, for more information regarding this.
Individuals interested in more information about rust can go to www.sbrusa.net to view a map of the United States showing areas scouted for rust and areas were rust has developed.
Missouri farmers, dealers and crop consultants may have soybean leaves examined for rust at the University of Missouri Plant Diagnostic Clinic for a $15 fee. Soybean leaves should be placed in moist paper towels and sealed in a plastic bag and expressed mailed to the clinic along with a completed information form. The information form and more instructions about collecting and mailing samples to the clinic are posted at http://soilplantlab.missouri.edu. Allen Wrather, Plant Pathologist, 573-379-5431.
For more information, contact Wayne Flanary at 660-446-3724 or Heather Benedict, 660-425-6434, University of Missouri Extension Regional Agronomists.