 The most significant disease threat to soybeans in the United States is soybean cyst nematode, also known as SCN. And as this pathogen spreads in North Dakota and Minnesota, it's going to threaten our driving production. I'm Sam Markel, and as an extension plant pathologist at NDSU, I'm concerned about soybean cyst nematode on dry beans, partly because you can take a yield hit before you even see symptoms. In this video today, we're going to talk about SCN biology, we're going to talk about symptoms, and we're going to talk about how to manage it. Although this pathogen is relatively new to Northern Minnesota and North Dakota, it was first found in the United States in 1954 in North Carolina. Over the next half century, it spread throughout the entire soybean growing region of the U.S., and by 2003, it was first found in North Dakota. Over the next decade, SCN spread from Richland County North to the Canadian border and west to the Missouri River, and by 2014, SCN was confirmed in 19 North Dakota counties. But just because SCN occurs in these counties doesn't necessarily mean its widespread or the egg levels are high. A grower-based SCN survey supported by the North Dakota Soybean Council has given us a much better idea of where soybean cyst is in North Dakota. These maps, compiled from thousands of soil samples taken between 2013 and 2015, show that most fields do not have SCN, or are inconclusive. Although moderate levels of SCN occur in multiple counties, the very high levels are really only in the southeastern part of the state. I'm Berlin Nelson, a soybean pathologist here at North Dakota State University, and I've been working with soybean cyst nematode for about 20 years. In this pot right here, you'll see we have some dry beans growing. These are infected with soybean cyst nematode. As a matter of fact, this pot is sitting in a water bath because it keeps the roots nice and warm, because that's what the nematode likes. One of the nice things about soybean cyst nematode is you can actually see the nematode on the roots of dry bean. When you see soybean cyst nematode on the roots of a dry bean plant, you're looking at a little white or cream-colored female. Her head is still in the root and her body is protruding from the root, so you can actually see it. You have to get the soil knocked away to be able to see it, and each one of those white females is called a cyst. They will eventually die, they will turn brown, she will be filled with eggs, and she'll fall off into the soil, and those eggs will overwinter in the soil in the body of the female, and then in the springtime the eggs can hatch and they can infect a dry bean plant. The stability and hardiness of the cyst is the reason SCN can spread so effectively. Cysts are easily moved when soil is moved, on equipment, blown in the wind, by moving water and by people. In 2015, SCN was found in North Dakota for the first time on dry beans in a commercial field in Cass County. The level of infection was low, but in 2016, SCN was found in a commercial kidney bean production field in Minnesota. This time it was causing yellowing and stunning of plants typical of the very severe infestations that we see in soybeans. This field will definitely have yield loss from SCN. This is a close-up of the light-colored live females from kidney bean roots and the brown cysts, which are the dead females filled with hundreds of eggs. This is the head of a second-stage juvenile larva of soybean cyst nematode as seen through a microscope. This is a stage that infects dry bean. The arrow points to a spear-like object called a stylet, which the nematode uses to puncture a hole in the root to begin the infection process. If you grow a susceptible crop such as dry bean on land infested with soybean cyst nematode, you will begin to increase the egg populations in the soil. Even though at first you may not detect any effects on your yields, and you may not even observe any above-ground symptoms of disease. Eventually, those populations will be high enough, and with favorable environmental conditions, you will have a yield loss. Research supported by the North Harvest Bean Growers Association has shown that soybean cysts can cause major reductions in dry bean yields. Most bean classes are thought to be susceptible, but black beans have shown some level of resistance. This image shows the damage to pinto bean caused by soybean cyst nematode. Observe the plants in the non-infested soil in the middle, and the plants growing in soil with 5,000 eggs per 100 cubic centimeters of soil on the left, and the plants growing in soil with 10,000 eggs per 100 cubic centimeters of soil on the right side. Notice the reduction in plant growth caused by soybean cysts and the lack of pods. There are many factors that will affect yield loss, such as environmental conditions during growing season, the soil type, and the bean class. One critical factor, however, is the egg numbers in the soil. Management strategies for STN on soybeans are pretty clear, and we can apply some of them to dry beans. The first step is to check your fields for STN. You do this by soil sampling. The best time is right around harvest when the STN populations are the highest. Concentrate in areas where STN may have moved into your field, like the field entrance, or maybe a low spot. Take 10 to 20 samples 6 to 8 inches deep and aim for the roots. Mix the sample up well and send it into the lab. Crop rotation is also very important to managing STN, and because soybean and dry bean are the only hosts, any other crop we grow in North Dakota should limit STN reproduction. You often see a 30 to 50% reduction in egg levels with just one year of rotation, but two to three years of rotation will likely reduce those levels even further. Resistance is not an option yet, but NDSU is working to identify resistance and incorporate it into dry bean varieties. Unfortunately, it's impossible to prevent the spread of the nematode, but you may be able to slow the spread if you know which of your cornfields are infested. Also, it's critical that if you purchase equipment from an area known to have STN, clean that equipment off where you bought it. NDSU has a team of scientists working on the STN threat to dry beans, and is thankful for the research funding received as we develop management tools and strategies for our region.