Along with many other problems a dry year creates, soybean cyst nematode can also thrive in these dry conditions.
The SCN Coalition wants U.S. soybean growers to understand the risks associated with higher population densities of soybean cyst nematode during hot and dry growing seasons.
“Weather can have a tremendous impact on soybean cyst nematode reproduction,” states Iowa State University Nematologist Greg Tylka. “We have data verifying that SCN is worse in hot, dry years. It’s not just because plants are stressed from drought, but also because the nematode is reproducing much quicker, raising population densities.”
Unfortunately, the life cycle of soybean cyst nematode speeds up during drought-like conditions. Because reproduction happens more quickly, more generations are created during a single growing season that ultimately leads to higher egg counts during fall soil sampling. Here in South Dakota, we would expect to have two to three generations in a normal season.
Due to the current conditions and the expected higher than normal egg production of SCN through this season, we would expect the egg counts to be higher and an increased yield loss. This makes fall the perfect time to test for SCN and this will help in making management decisions for the following year. Fall sampling can be done just prior to harvest, looking at areas within the bean field that appear shorter, less thrifty, or areas within a field that are known to already have SCN. Or after harvest where your yield monitor was indicating areas within a field that are lower in yield, this would also be a good time to test those areas for SCN.
Managing SCN involves more than just planting an SCN-resistant variety. You need to know your numbers. Here’s why:
• Nearly all SCN-resistant varieties have the same source of resistance: PI 88788.
• SCN populations are adapting and reproducing on PI 88788 – they’re becoming resistant to the resistance.
• As SCN reproduction increases, yield decreases.
The first and most important step in management of SCN is identification. Soil sampling is a means of determining both the presence of the nematode as well as its population levels. Fall sampling allows adequate time to employ SCN management techniques for the coming year, but soil sampling at any time can be useful.
To sample soil for SCN, use a soil probe to obtain 20 soil cores at a depth of 0-6 inches, ensuring areas such as field entrances, low yielding areas, and/or along the fence line are included.
Larger fields should be divided into 10-20 acre sections. Sampling for SCN can be done any time provided the soil is not too wet. which for many areas in the state is not the case this year, and not frozen so that a spade or soil probe can be inserted down to that 0-6 inch depth. Mix the 20 soil cores well and send a minimum of one pint of soil to (mail or drop off):
SDSU Plant Diagnostic Clinic
1451 Stadium Rd
SPSB 153, Box 2108
Brookings, SD 57007
605-688-5545
