Slugs Causing Concern Earlier Than Normal

Slugs hatched out earlier than normal and have reached a size that can cause noticeable feeding injury much sooner.  For growers who have experienced slug issues in the past, it is critical that fields be scouted NOW. If plants have emerged and have leaves, look for the telltale signs of slug feeding. The growing point of soybeans is between the cotyledons as the plant emerges from the soil.  Thus, the slug is easily able to reach and feed on both the cotyledons and the growing point, making it much easier for slugs to kill the soybean plant as it emerges from the soil. For crops not yet or just now emerging, or yet to be planted, care should be taken to determine if slugs are present and lying in wait...read full story

Conservation System Management Considerations

Conservation tillage systems such as no-tillage have a positive impact on soil productivity…especially under extreme wet or dry conditions. Current research shows that the tillage system has little effect on N, P and K crop needs. However, the timing and method of application are vitally important to no-tillage success, especially in cold-wet soil conditions where mineralization of soil nutrients is much slower compared to conventional tillage ...read full story

Soybean Seedling Diseases – What to Look for in 2012

Soybean seed and seedlings are vulnerable to a number of soil borne pathogens in the early spring. The conditions for these diseases have been quite variable this year in Ohio, with some areas very dry and cool while other locations have been warm and wet…read full story

Entomological Musings This Spring

Bean leaf beetles. Just as producers transition from corn planting to soybeans, observations of bean leaf beetles are becoming more common, especially in central Illinois. Bean leaf beetles overwinter in protected areas (beneath plant debris), and survival this past winter was undoubtedly quite good. Favorite overwintering sites include wooded areas adjacent to stands of alfalfa. In the spring, dormancy of the adults is broken, and they often move initially into alfalfa. Soybean seedlings in early-planted fields are most at risk to intensive feeding by the overwintering population.

Rescue treatments for bean leaf beetles in seedling soybeans are typically not warranted given the densities required to cause economic losses: 16 beetles per foot of row for the early seedling stage and 39 for the V2 stage and beyond. In light of the mild winter, I encourage producers to scout fields carefully for bean leaf beetles this spring. Pay particular attention to soybean fields that are planted first in your area of the state…read full story

On Farm Iron Deficiency Chlorosis Management Strip Trials

Four field trials have been conducted since 2010. At two of the locations there was severe yield reduction from IDC. In severe areas, in-furrow application of an EDDHA-Fe fertilizer significantly increased yield by an average of 5 to 6 bushels across the entire trial, and by as much as 10 bu/ac or more in the severe areas. The oats cover has also shown some positive yield benefits in severe IDC field areas. When comparing varieties, there was a large yield benefit with the variety that was less tolerant to IDC, but the tolerant variety still overall produced a higher yield level when IDC was present ...read full story

New SCN-resistant soybean varieties containing effective new genes are in the works.

Despite valiant efforts by farmers and the seed industry to control SCN, it is still considered to be the #1 yield robber in soybean production. It invades roots, feeds, then reproduces 250-fold. It can reduce yield as much as 70 percent under severe infestations and drought conditions; under more moderate conditions it can cause 30 percent yield loss without visual symptoms.

An army of researchers funded with soybean checkoff dollars has been working to find that elusive solution to the $1.5 billion annual economic loss. The solution, improved genetic resistance, is a ways off but it is coming.

Plant breeders at Midwest universities, in partnership with the USDA have been searching the nation’s germplasm collection for novel genes to complement those in today’s varieties. Several breeding lines containing these new genes have been recently developed and are under rigorous testing. Commercial SCN-resistant soybean varieties containing these new genes could be available as early as 2017.

Until then, farmers will need to rely on improved management strategies including old school cultural practices and emerging technologies to limit yield loss to SCN.

Nematicide seed treatments are emerging as the next wave of options available to soybean farmers to manage SCN. That’s why the North Central Soybean Research Program is evaluating nematicide seed treatments across a 12 state region.

Using commercially treated seed, plant pathologists evaluated the effectiveness of this technology by determining the SCN population at planting and again in the same location, after harvest. The numbers tell the story—an uncertain story. There was no clear benefit to the seed treatments in the 2011 field trials. Keep in mind however; it is extremely difficult to get a clear picture of performance based on one year of field data so the study will be repeated in 2012 and 2013.

In other studies, researchers are looking at levels of SCN reproduction on roots of soybean varieties labeled as resistant. The results are surprising: Not all SCN-resistant soybean varieties manage SCN equally; some varieties still have a large number of SCN on the roots at harvest. Repeated use of these varieties allows the SCN population to continue to grow—and feed on soybean roots.  However, field studies also show that some of these same varieties remain high-yielding under pressure from SCN. More work is needed in this area to better understand this relationship. Meanwhile, check with your state Extension specialist for information on SCN reproduction on commercial soybean varieties to determine if your soybean variety is actually lowering SCN numbers.

Old school cultural practices like rotating soybean with corn or other non-host crops is still a great way to lower SCN populations. Many farmers have shifted to a soybean-corn-corn rotation strategy to benefit from higher margins realized from corn production. Older research clearly shows a decrease in SCN numbers when soybean is planted following one year of corn. It is unclear whether a long-term soybean-corn-corn management strategy significantly reduces SCN numbers—and increases soybean yield.

Until a genetic solution is discovered that eliminates SCN feeding and reproduction several management tactics will need to be employed to reduce yield loss from this pest. Seed treatments, planting SCN resistant varieties, crop rotation, and monitoring SCN numbers within fields are all critical.

That’s your soybean checkoff. Delivering results.

1.  Improve the quality of the root zone. This will improve water-holding capacity of the soil and plant resiliency. Healthy roots enable the vegetative portion of the plant to take full advantage of photosynthetic capacity.

• Manage SCN populations. This goes beyond purchasing seed labeled as SCN-resistant. Regularly test for SCN, rotate varieties grown in fields and sources of resistance to keep SCN numbers low.
• Use fungicide and insecticide seed treatments.  Research has shown that soybean seed planted with both yield more.
• Drain soils—tile is inexpensive.
• Reduce soil compaction
• Improve soil fertility levels. Be sure you have enough P, K, and micronutrients but be sensitive to environment.

2.  Variety selection.  If you are planting a variety that is two years old or more you may be giving up $13 or more per acre.

3.  Plant early to take advantage of as much of the growing season as you can. Delayed planting can cause 0.3 to 0.7 bushels/acre/day yield loss after May 10.

4.  Row spacing.  The greatest yield advantage is from 15- or 10-inch row spacing.  Yield gains of 4.5 bushels/acre have been proven for narrow rows compared to 30 inch rows in Midwest trials.

5.  Plant population.  Agronomists from several Midwest universities have shown that a final stand of 100,000 to 125,000 plants per acre will provide the best return on investment.

6.  Crop rotation helps reduce the severity of certain diseases and increases yield of soybean and corn crops.

7.  Manage weeds early.  Weeds compete with soybean for water and nutrients and sunlight.

• Use a combination of a pre-emergent herbicide for early weed control then go for one application of a post- emergent herbicide to clean up the rest.
• Use multiple modes of action to reduce the possibility of a herbicide-resistant weed population developing.

8.  Hire a crop advisor if you are not monitoring your fields yourself.  A good crop advisor will monitor your for yield robbing diseases, insects and fertility problems.  Crop advisors are always up-to-date on emerging problems and management recommendations.  Identifying problems early can save you big money.

9.   Strive for a clean harvest for both soybeans and corn.  Certain fungal pathogens like the one that causes Sudden death syndrome (SDS) survive on corn residue and dropped corn kernels.  A clean corn harvest may reduce the severity of SDS the following year.

10.  GET INFORMED!  Take advantage of production meetings sponsored by Extension educators.  These meetings are packed with the latest research findings and best management practices for producing corn and soybeans.

It’s a serious threat

Brown marmorated stink bug

Midwest farmers are faced with another harmful pest from Asia, the brown marmorated stink bug (BMSB). Its name describes its color pattern (marmorated, meaning marble-like or speckled) on its shield-like back, and what it smells like if it’s threatened or squished. However, its name does not tell the story of how this new pest is devastating parts of North America.

Over the past decade, the BMSB has moved into homes, fields and orchards in 33 states. It has a wide host range similar to Japanese beetle, including corn, soybean, fruits and vegetables. The BMSB is serious threat to agriculture and is wide-spread in the Eastern United States with additional known populations in California and Oregon. However, because of the BMSB’s recent detection in the Midwest, a thorough survey for this pest has not been conducted.

One thing is for certain, though: BMSB can take a toll on soybeans, although so far yield loss has been limited to the east coast. The insect, which is distinguished by white banding on the antennae and legs, a striped abdomen and a pale underside, tends to feed on soybean seeds through the pod, damaging the yield potential. During seed formation, BMSB can puncture tissue and cause deformations. The seed coat can be damaged, and overall the seeds are smaller and shriveled.

And while BMSB feeding appears to slow or delay development of soybeans, the insect’s appetite goes far afield. Corn is on its menu too. So are fruits and vegetables. In fact, there’s little it doesn’t attack with vigor, piercing and sucking leaves, stems, fruits, and seeds.

Accurate identification is essential

From left: adult brown marmorated stink bug (pest); green stink bug nymph (pest); adult and nymph brown stink bug (pest); and adult spined soldier bug (beneficial).

Scouting will reveal the presence of many species of stink bugs. While most stink bugs are herbivores, one sticks out as beneficial – that is, the BMSB’s cousin, the spined soldier bug, commonly found in Midwest soybean fields. Both the immature and adult stink bugs of this species are predatory, and will kill many soybean pests.

The entire agricultural sector is on a steep learning curve, working towards an integrated pest management program to control the BMSB. That’s a real challenge, because it’s different on so many levels.

Multicolored Asian lady beetle

1. Like another invasive pest, the multi-colored Asian lady beetle, the BMSB isn’t limited to the field. It survives the winter as an adult by entering houses and structures, and becoming a noxious pest.
2. Both the immature stage (nymphs) and adults feed on host plants.
3. Generations overlap and can feed throughout most of the summer.
4. Treatment thresholds have not been developed.

It’s unlikely that BMSB will show up in great numbers in soybean fields across the Midwest this summer. It usually takes two to three years to become problematic once it is introduced. They usually become problematic first in fruit trees and vegetables.  It is possible, that in the Midwest, they may target corn and soybean early in the summer because of the low abundance of other hosts. Scouting will prove or disprove that prediction.

If you find stink bugs in your soybean or corn fields, and you are not certain which species you have, contact your state’s Extension entomologist.  They will assist you in accurately identifying the insect and providing options for management.

Soybean yield is often limited by soilborne pathogens. The average United States soybean yield is 43.9 bushels per acre or only about 27 percent of known yield potential (160 bushels per acre). The difference between harvested yield and potential yield is lost to a plethora of environmental stresses such as heat and drought as well as a complex of poorly understood soilborne pathogens.  These pathogens invade plant roots causing tissue decay, a reduction in the number of root tips, a decrease in nodule size and loss of root function.

Major yield losses are found in areas where soils have high clay content or remain saturated for long periods of time. The key to improving soybean yield is to improve root health.

One aspect of improving root health is increasing the number of roots. Water and nutrients are absorbed into the root just behind the root tip, so increasing the number of roots means more water and nutrients can be absorbed.  Healthy roots trigger faster plant growth and seed development when environmental conditions are not growth limiting.

In addition to anchoring the plant, the soybean root is responsible for absorbing large amounts of water and nutrients and then transporting them to the stem and leaves. When roots are damaged the plant’s ability to obtain water and nutrients is greatly reduced. Preventing  damage to the root removes the stress and helps avoid unnecessary yield loss.

The most important pathogens associated with seedling root health include the soybean cyst nematode, Pythium species, Phytophthora sojae, Rhizoctonia solani, and Fusarium species. Iowa State University researchers found that each of these pathogens has been found to impair root health alone and in combination with each other.

Pythium species cause seed decay, pre-emergence damping off and early post-emergence seedling death. Seed infected with Pythium species may decay before germination and as they do, become soft and rotted. Phytophthora sojae also causes a soft, wet rot of seed or seedling tissue similar to that of Pythium species. Infected seedlings may die prior to emerging from the soil or shortly thereafter.

Symptoms of Rhizoctonia solani infection generally show up on seedlings as dry, dark reddish-brown lesions just above the soil line. Seedling loss from Rhizoctonia seedling blight is less common that from Pythium seed decay and Phytophthora root rot but when present, stand loss can be severe.

The traditional soybean-corn production system creates a monoculture that creates an environment that promotes the build-up of root-infecting pathogens.

Researchers at Iowa State University report that within the soybean- corn rotation, there may have an inadvertent increase of populations of root-infecting pathogens, thereby increasing root damage. For example, there are reports from Ohio State University that isolates of Pythium species and Rhizoctonia solani are becoming resistant to commonly used fungicide seed treatments. They suggest that if these isolates are pathogenic to both soybean and corn, it is likely the pathogen inoculum is also increasing in the field. Thus, an increased knowledge of the role of Pythium species and Rhizoctonia solani in the soybean-corn rotation is necessary for improving yield.

Improving root health

The first 10 to 14 days following soybean planting is the window of opportunity for Pythium and other soilborne fungi to infect the plant. Implement practices that promote quick germination and seedling emergence to prevent infection.

• Plant high quality seed and plant into a good seed bed
• Plant seed that has resistance to Phytophthora sojae. Specific resistance is controlled by major resistance genes such as Rps1k. In addition, select varieties with high partial resistance (tolerance) when possible.
• Plant where drainage is adequate, or improve drainage if possible. Avoid low areas of fields, especially if a field has a history of seedling or root rot problems.
• Consider that germination will be quickest when soil temperatures are greater than 65°F

What to do if seedling diseases are present

• If dead plants are scattered throughout the field, and no significant stand reduction is apparent, then no action is needed if the disease is Pythium or Rhizoctonia damping off.
• If seedling loss is severe, consult a certified crop advisor to determine if replanting is necessary. Replanting is not always necessary.
• Take good disease notes and use preventive measures such as seed treatment or resistant varieties to reduce the likelihood of a disease problem in the next soybean crop.

If replanting is necessary

If poor stands are due to diseases, fungicide seed treatments can be used in replanting to avoid further damping off, especially for Rhizoctonia and Phytophthora. If poor stands are due to a low germination rate, a seed treatment cannot improve seed germination rate or seed vigor.

No-till soybean field. Photo credit: Iowa State University

No-till farming is a growing practice in many areas of the United States. An estimated 50 percent of the acres planted to soybeans in 2009 were done so without tillage according to a recent USDA Economic Research Service report. Farmers are adapting no-till soybean production at a faster rate than they are for corn, cotton and rice.

There are many motives for adapting no-till. Some see it as a “greener” way to produce a global food supply while conserving soil and water resources so generations to come will be able to enjoy the benefits we do. Others see it as building resiliency into a production system faced with challenges of floods, drought, diseases and pests influenced in part by changes in climate. No matter what the reason, no-till practitioners are emphatic in their belief that it contributes to the sustainability of soybean production.

Long time practitioners of no-till admit there is no one way of doing it. Soils respond differently to no-till, so no single piece of equipment or common practice guarantees success. Successful no-tillers admit, however, they’ve learned from their mistakes and from listening to others.

Jim Specht, University of Nebraska, professor of agronomy offers these words of advice for getting the most out of no-till soybean production systems.

Plant early - Iowa State University reports delayed planting of high yielding fields results in a yield loss of 0.3 to 0.7 bushels per acre per day with the largest yield reductions occurring after May 10.  In Nebraska, the yield penalty for delayed planting is between 0.3 and 0.6 bushels per acre per day of planting delay after May 1.

Choose soybean varieties wisely - Variety selection for field-specific problems such as diseases and SCN is important for success in no-till.  Loren Giesler, University of Nebraska Extension plant pathologist agrees and says, “Farmers who know they have SCN can gain, on average, five to six bushels per acre simply by planting a SCN-resistant soybean variety, according to yield trials.”

Use a fungicide seed treatment - There is no doubt that seed-applied fungicides improve stand establishment in cool soils common in no-till fields. This is especially important to famers who are planting fewer seeds per acre to reduce input costs without sacrificing yield. To them, every plant counts. To others, it’s insurance. University studies show that soybeans are very resilient and will compensate for a few missing plants.

The benefit of using an insecticide seed treatment is unclear. Some university research shows that an insecticide seed treatment alone doesn’t always improve yield. The research also shows yield increases are inconsistent when an insecticide/fungicide seed treatment is used. Although the industry doesn’t have a complete understanding of how to use this technology, the observed benefits can’t be ignored.

Consider strip tilling soybeans in heavy residue situations. For those soybean producers whose prior crop corn yields were high, there will be a lot of corn residue left behind.  Specht says, “For every pound of grain removed there is a pound of residue left behind so, a 250 bushel per acre corn crop leaves behind 14,336 pounds of residue per acre.” He suggests producers will get better planter soil closure over the soybean seed if a strip of corn residue has been cleared.  The soil in that strip also warms up faster, which benefits early planted soybeans.

Every year more farmers are seeing the wisdom and rewards — both economic and personal — in no-till soybean production systems. Because each farm is different, there’s no single formula for sustainable success in no-till, but these principles are a good place to begin.

This year, many Midwest farmers discovered first-hand the effect of root infection by the fungal pathogen that causes sudden death syndrome (SDS): yield losses of 40 percent were recorded in some fields. But it’s not just SDS that is limiting yield in soybean fields. Wounds caused by soybean cyst nematodes (SCN) and by maturing females serve as entry points for other soilborne pathogens. Brown stem rot (BSR) also infects roots of young seedlings and is often found in the presence of SCN.

Each disease can cause significant yield loss, up to 50 percent under optimal conditions. Even worse is the interaction between SCN and the fungal pathogens that cause SDS and BSR which can cause even more yield loss.

First discovered in 1971 in Arkansas, SDS has quickly spread throughout the Soybean Belt and is now found in areas of South Dakota and in 23 counties in Minnesota. It is likely spreading north with the movement of SCN; the SDS fungus is commonly found in the cysts. Because of this close association with between SDS and SCN, assume that if you have one or the other, you probably have both.

BSR has been found in nearly all Midwest soybean producing states. The increase in the incidence of BSR is thought to be a result of a monoculture created by the traditional soybean corn rotation which encourages a build-up of the BSR pathogen in the soil. Like SDS, the fungus that results in BSR infects the root early in the growing season and is favored by cool, wet soils.

Minimizing yield loss from SDS and BSR begins with managing SCN in fields where combinations of these stressors co-exist. SCN cannot be eliminated once it becomes established in a field, but its influence on other soilborne pathogens can be reduced with proper management.

A new publication is now available to help soybean producers manage SCN. The SCN Management Guide, fifth edition provides soybean producers with science-based information generated from many years of checkoff funded research that is proven to reduce SCN populations.

With currently available management options, it is much easier to keep low numbers low than it is to try and drive high SCN numbers down. By managing SCN you can:

• Improve soybean root and plant health and yield;
• Keep SCN numbers low; and
• Preserve the yield potential of resistant varieties

Because no single management practice will meet all three goals, you must use an integrated approach that combines several components. Chief among these are the use of varieties resistant to SCN and with good field tolerance to SDS and BSR, rotation with non-host crops when possible, maintaining a well-drained seedbed, use of fungicide and insecticide seed treatments to promote early seedling health.

Click on the Free Publications link above to receive your free print copy of the SCN Management Guide, or view online – see sidebar to the right.

Farmers will need to employ multiple tactics to improve soybean yield. The most important will be employing management tactics that improve soybean root health.

A healthy soybean root is an important component to soybean yield. A soybean plant with a healthy root system is more efficient in taking up water and nutrients, and can better withstand the effects of infection by soilborne pathogens and soybean cyst nematode.

This year, many Midwest farmers discovered first-hand the effect of root infection by the fungal pathogen that causes sudden death syndrome: yield losses of 40 percent were recorded in some fields.But it’s not just sudden death syndrome that is limiting yield potential in soybean fields. Soybean cyst nematode remains the most serious nematode pest of soybean in the United States.

For many years early soybean planting has contributed to soybean seedling damping off, which reduces stand establishment. Pythium, Rhizoctonia root and stem rot, Phytophthora root rot, and Charcoal rot are root and stem diseases caused by soilborne pathogens and all are known to cause significant yield loss. It is interesting to note that research conducted at Iowa State University discovered that some isolates of Pythium recovered from diseased soybean seedlings were also highly aggressive against corn. This suggests that management tactics to reduce the impact of Pythium species must be utilized in both the soybean and corn crops.

Reducing yield loss from these soybean diseases begins with improving root health. Improving root health begins with refining management tactics. Soilborne pathogens are best managed with a combination of improved soil drainage, fungicide seed treatments, planting high quality seed, crop rotation and tillage practices that minimize soil compaction zones. These management tactics reduce inoculum in the field and limit the amount of water available for the pathogens to germinate and infect.

The importance of a well drained soil became apparent this year as farmers noticed signs of SDS first in low lying field areas and along edges of water ways. Improving drainage in these areas will reduce the severity of SDS and also diseases caused by Pythium and Phytophthora. If drainage in these areas cannot be improved, farmers should consider planting them last.

The importance of managing SCN cannot be overstated. SCN feeding on roots creates openings for opportunistic infection by soilborne pathogens. Researchers recently found greater levels of Pythium species and Phytophthora sojae in roots of SCN susceptible soybean plants. Previous research showed that SDS was more severe in areas also known to be populated by SCN.

Fungicide seed treatments for soybean are an emerging tool that farmers can use to protect yield. Some data suggest that the combination of a fungicide and insecticide seed treatment produces greater yield than using either of the two alone. This suggests that the management tactics to control early season diseases and insects should begin at planting and not after emergence. In other words, Manage Soybeans from the Ground Up to increase soybean yield.

That’s your soybean checkoff. Delivering Results.

Symptoms of SDS on soybean leaves

Sudden death syndrome (SDS) is ravaging many Midwest soybean fields.

Farmers watched anxiously as low-lying areas of some fields suspiciously turned brown then watched those small areas grow into much larger areas of dying plants. SDS is showing up on a scale not seen since it hit Illinois soybean fields in the early 1990s. This year’s yield losses to SDS are expected to exceed 20 percent in some fields.

The cause of the disease is a soil fungus that is widespread throughout the Midwest. It infects the soybean root early in the plant’s development; later, the pathogen rapidly kills the plant during pod set and pod filling. Infection of the soybean root is worsened by cool, rainy weather throughout the first half of the growing season as well as soil compaction and poor drainage.

Development of SDS depends upon many factors including planting date, tillage, variety of soybean, and the presence of other stresses such as SCN. Early planted soybeans tend to be more heavily damaged than later planted beans because of the more favorable conditions for infection by the soilborne fungus.

The impact of tillage on SDS remains unclear. Reduced tillage, including no-till, may influence the presence of the disease because corn residue causes slower warming and drying of the soil. Corn residue, including dropped corn kernels, harbors the fungus that causes the disease, possibly increasing the amount of the fungus in the soil. However, mature no-till fields tend to drain more quickly than conventionally tilled fields reducing the saturated seed zones that promote infection of the root by the fungus.

Crop rotation is of limited value. University of Illinois researchers report finding SDS in continuously grown soybeans, soybeans following one or two years of corn, and in fields that had been out of soybean production for many years. They reported that the fungus that causes SDS can persist in the soil for many years even without a host crop.

SDS can be more severe in field areas also infested with SCN. Feeding by the nematode on soybean roots adds additional stress that often increases the impact and severity of SDS. Researchers have discovered that cysts can contain the fungal pathogen that causes SDS. However, the two problems are known to exist independently.

Farmers planting maturity group II and I soybeans may be at greater risk of seeing SDS in their fields because soybeans in those maturity groups generally have lower levels of field tolerance to the disease. Although public and private plant breeders are working hard to improve the plant’s performance against the fungus, it will be another 5 to 10 years before greater levels of protection are in place in those maturity groups.

Checkoff-funded researchers throughout the Midwest are working feverishly to solve the SDS problem. Emphasis is being placed on the development of breeding lines with improved tolerance to SDS and screening and categorizing the response of commercial soybean varieties.

Aphids on soybean leaves and petioles

Soybean aphid is the most significant above-ground pest that farmers face today.

Aphids reduce soybean yield and farmer profitability. They may even transmit viral diseases that can reduce seed quality at harvest. They’re born pregnant so populations can explode almost as quickly as you can turn your head.

Farmers could be facing another year of heavy aphid populations. According to Matt O’Neal, Iowa State University soybean entomologist, he and his Midwest colleagues logged record numbers of aphids headed to overwintering sites in 2009. “The numbers of aphids found on buckthorn last fall were so high that leaves were falling off the plant,” says O’Neal. However, a follow-up visit to those same areas found very few eggs. “This is a bit of a mystery to us,” admits O’Neal. He also admits they’ve seen this before and if history repeats itself, farmers will be spraying for aphids in late July or early August.

“One well-timed foliar application applied after the aphid population exceeds the economic threshold will protect yield and increase profits in most situations,” says O’Neal.

Timing is very important, however.

“Adding insecticide to an early-season glyphosate application as ‘insurance’ doesn’t make sense, says David Ragsdale, University of Minnesota entomologist. Weeds need to be controlled early because they compete for water, nutrients and sunlight. However, aphid populations don’t reach the economic threshold until much later.

The timing of a fungicide application may overlap with the management of soybean aphid. However, many fungicides are toxic to naturally occurring fungi that attack aphids and their use could lead to a subsequent increase in aphid numbers. Farmers who apply fungicide either alone or in a tank mix should monitor those fields for aphid population growth.

Some marketing programs encourage the prophylactic use of fungicides and insecticides as a tactic for managing soybean. Although yield gains using this tactic have been recorded, the results have been inconsistent and thus the benefit this management tactic remains unclear. Ragsdale believes there is a better way.

“Aphid management requires multiple tactics,” states Ragsdale. He advises farmers against becoming too reliant on the “quick fixes” when making management decisions. “Using multiple tactics including cultural, chemical, and biological control is the most effective aphid management plan for long-term, profitable soybean production,” he concludes.

Both Ragsdale and O’Neal recommend regular scouting and a 250-aphid-per-plant threshold for spraying to conserve the natural enemies that prey on aphids. Scout once or twice a week beginning in late June or early July, no later than the R1 (beginning bloom) soybean growth stage, and continue through pod fill. Pay particular attention to late-planted fields, or fields under moisture stress.