Newsletter Archive

The soybean cyst nematode (SCN) is one of Iowa's most serious and persistent soybean pests. The nematode has the potential to cause devastating yield losses, population densities can increase very rapidly within a single growing season, and dormant eggs can survive for more than a decade in infested soils in the absence of soybeans. Random surveys funded by the soybean checkoff in 1995-1996 and again in 2006-2007 revealed that 70 to 75 percent of fields in Iowa are infested with nematode.

Iowa farmers are using cover crops for erosion control and soil nutrient and pest management in their fields. There are two aspects of cover crops that relate to the biology and management of the soybean cyst nematode (SCN).

The soybean cyst nematode (SCN) is one of the most damaging pests of soybean in Iowa and the Midwest. SCN can cause foliar symptoms of soybean sudden death syndrome (SDS) to occur earlier in the season and to become more severe, leading to increased yield losses from the disease.

Plant-parasitic nematodes are microscopic worms that live in the soil and feed on plant roots. Nematodes that feed on corn occur in almost every field in Iowa, but most do not reduce corn yields measurably until they increase to high population densities (numbers). Fall is not a recommended time to check fields for damaging population densities of nematodes that feed on corn. 

Now that harvest of this year’s crops is nearly complete in Iowa, it’s time to begin planning for the next growing season. For soybeans, that means taking soil samples to determine SCN population densities. Fall is a perfect time to do this.

It is hard to think about planting crops with the brutally cold weather we have been experiencing in Iowa the past several weeks. But warm weather and planting season will be here in a matter of weeks. As plans are being made for the 2014 crops, farmers and agronomists should be aware that fields planted to soybeans this year may have unusually high soybean cyst nematode (SCN) numbers if soybeans were grown in the fields in 2012. The number of SCN eggs in the soil at the time of planting is a major factor determining how much damage and yield loss SCN will cause.

An effective way to manage the soybean cyst nematode (SCN) is to grow SCN-resistant soybean varieties. Resistant varieties can yield well in fields infested with the nematode and can keep SCN population densities (numbers) from greatly increasing.

Iowa farmers produce soybeans profitably in fields infested with the soybean cyst nematode (SCN) by growing SCN-resistant soybean varieties that yield well and prevent large increases in SCN egg population densities. There are hundreds of SCN-resistant soybean varieties for Iowa. Almost all of the varieties contain SCN resistance genes from a single breeding line, called PI 88788. Because of widespread, repeated use of varieties with the same PI 88788 source of resistance, many SCN populations have developed increased reproduction on that type of resistance.

As we work to complete harvest and put the finishing touches on the 2013 growing season, it is not too early to start thinking about 2014 crops. Results of soil samples collected in the next few weeks from fields in which soybeans will be grown in 2014 could mean the difference between “so-so” and profitable yields next year.

Crisp, clear fall days are perfect for splitting firewood, tilling the garden under and collecting soil samples to check fields for the soybean cyst nematode (SCN). Although soil sampling for SCN might not be on most people’s list of favorite autumn chores, fall is a great time to sample fields for this pest. Reasons to sample for SCN include to check for the presence of the nematode in fields and to monitor SCN numbers in fields known to be infested with the pest.

The soybean cyst nematode is one of the most damaging pests of soybean in Iowa and throughout the midwest. The amount of yield loss that occurs is directly related to the SCN egg population densities (numbers) in the soil. Keeping SCN egg population densities from increasing to high levels is needed to maintain profitable soybean production in SCN-infested fields. An effective way to produce high soybean yields and keep SCN egg population densities in check is to grow SCN-resistant soybean varieties. 

The soybean cyst nematode (SCN) remains a leading yield robber of soybeans in Iowa and much of the Midwest. The presence of SCN in the field may not be apparent by appearance of visual symptoms (aboveground stunting and/or yellowing) for years after the nematode is introduced in a field. An easy way to check fields for the presence of SCN during the growing season is to look for telltale swollen, white SCN females on soybean roots. The SCN females are small, about the size of a period at the end of a sentence on a printed page.

Profitable soybean yields can be produced in fields infested with the soybean cyst nematode (SCN) by growing SCN-resistant soybean varieties. SCN-resistant soybeans can keep SCN population densities from increasing and produce high yields. Each year, Iowa State University compiles a list of SCN-resistant soybean varieties that are available to Iowa soybean farmers for the upcoming growing season. The list is published with support from the Iowa Soybean Association.

Growing soybean varieties with resistance to the soybean cyst nematode (SCN) is an excellent way to manage this pervasive and serious soybean pest. 

The soybean cyst nematode (SCN) is a serious yield-reducing pathogen of soybeans. It is present in many fields throughout the Midwest, wherever soybeans are grown. To produce profitable soybean yields in fields infested with SCN, farmers should grow SCN-resistant soybean varieties. SCN-resistant soybeans can produce high yields while keeping SCN population densities from increasing.

In past years, sudden death syndrome (SDS) has appeared during the last week of July of the first week of August in Iowa. Therefore we anticipate symptoms of SDS will begin appearing in the state within the next couple of weeks. Although we do not expect SDS to be as widespread or as severe as the 2010 growing season, there have been some Iowa counties that have received higher-than-normal precipitation. We expect the risk of SDS in these counties to be higher since disease development is favored by wet conditions. 

A very quick and easy way to check for the soybean cyst nematode (SCN) is to dig roots and look for the presence of the telltale, swollen, white females on soybean roots. This technique is effective for checking fields for the presence of this serious yield-limiting pest and also for checking to see if SCN populations are building up on SCN-resistant soybean varieties.

This 62-page field guide is designed as a resource for agronomists and farmers to manage soybean cyst nematode. Soybean cyst nematode is the most economically significant pest of soybeans in Iowa and has been found in 98 of the 99 Iowa counties. Infested soybean plants often show no symptoms other than reduced yield.

The amount of damage caused by the soybean cyst nematode (SCN) is determined, in large part, by the population densities or numbers of the nematode present in the field. More severe yield losses generally occur in fields with high SCN population densities compared to damage in fields with low or moderate numbers of SCN. Long-term, profitable soybean production in fields infested with SCN requires growing SCN-resistant soybeans and nonhost crops, such as corn, to keep nematode population densities in check

The soybean cyst nematode (SCN) is one of the most serious soil-borne pathogens of soybean in Iowa and throughout the midwest. Juveniles of this microscopic worm hatch from eggs in the spring, then burrow into soybean roots, where they attach to the vascular tissue of the plant and feed. Developing SCN females get progressively larger as they mature, until their fully-expanded, lemon-shaped bodies rupture out of the root and become visible on the root surface.

Although the soybean cyst nematode (SCN) is one of the most persistent and destructive pests of soybean in Iowa and the midwest, the potential to underestimate the nematode's yield-reducing effects is great because damage from SCN is not readily apparent in the field during growing seasons with adequate to excess moisture. The need to take the threat of SCN seriously was recently reviewed in an ICM News article. Fortunately, fields can be checked for the presence of SCN in the spring through soil sampling. 

As if the direct effects of Iowa's hot, dry growing season on crops were not damaging enough, the soybean cyst nematode (SCN) probably will be more damaging this year than in the past two decades due to the lingering drought conditions. 

The soybean cyst nematode (SCN) continues to be a major yield-reducing pathogen of soybeans in Iowa, and it occurs in up to 75 percent of fields in the state. Growing SCN-resistant soybeans is an important part of managing SCN. Results from Iowa State University’s nine SCN-resistant variety trial experiments in 2013 illustrate how resistant varieties can produce high yields and suppress the buildup of the nematode in infested fields.