Testing for the presence of soybean cyst nematode


Tony Nye - OSU Extension



What will the crop year 2022 look like? I think that can be answered one way – it will depend.

Mother Nature always being the one factor we can’t control. Things probably certain will be continued supply chain woes, increased fertilizer and herbicide costs along with seed, land and machinery costs.

The uncertainty that goes along with this will probably have area producers somewhat frustrated in the coming months.

Producers will have need to have a plan and identify those things they will be able to control within their operations. A couple items in their control is soil testing (if not current) to help determine accurate fertility needs, better weed management that may help lessen herbicide costs and identify other factors that could impact next year’s yields thus impact farm profitability.

One factor that farmers could do this fall is to test for the presence of soybean cyst nematode (SCN).

Soybean cyst nematode (SCN) remains the most economically important pathogen of soybean because it can cause yield loss between 15 and 30% with absolutely no visible symptoms. Resistance to SCN remains the most effective management strategy when rotating to a non-host crop is not an option.

The predominant source of resistance in most commercially available soybean cultivars comes from Plant Introduction (PI) 88788, which confers resistance to SCN Type 0 (formerly race 3). Soybean varieties labeled ‘SCN-resistant’ most likely have resistance from PI 88788.

The use of the same source of resistance over the past 20 years has placed selection pressure on SCN populations resulting in a shift in virulence, leading to adaption to now infect PI 88788-derived resistant soybean cultivars. In other words, nematodes reproduce at higher levels than before on soybeans developed with PI 88788 resistance.

According to Horacio Lopez-Nicora, nematology and soybean pathology specialist at Ohio State University, SCN is silently gaining territory in Ohio as SCN numbers are rising. The ability to reproduce on soybean cultivars with ‘SCN-resistance’ will lead to an imminent loss in our battle to protect Ohio soybean production.

To act, we need to know our numbers. Managing SCN begins with an adequate and correct soil sample. The SCN Coalition has launched its next phase of raising awareness of SCN distribution and its virulence profile in the U.S. We are excited to continue sampling soybean fields in Ohio to test for SCN with funding from the Ohio Soybean Council and The SCN Coalition.

Our goal is to sample more soybean fields, targeting those that have consistently been yielding low, under continuous soybean or double crop, and with weed issues.

Fall is a great time to sample for SCN and we are excited to help with this task by processing up to TWO soil samples, per grower, to be tested for SCN, free of charge. Identifying the presence of SCN in a field will help determine best management strategies.

When should you sample for SCN?

He suggests fall is the best time to sample for SCN. After soybean plants are harvested, a soil test will reveal if SCN is present and at what levels. Knowing your SCN numbers in fall will give enough time to plan for next year and to identify the best management practices.

How should you collect soil samples for SCN? Different sampling strategies can be used to collect soil sample for SCN testing, including those used for soil fertility sampling.

We strongly recommend using a 1-inch-diameter cylindrical probe to collect 15 to 20 (more is better) soil cores, 8 inches deep, for every 20 acres. Collect these soil cores in a zig-zag pattern across an area similar in soil texture and cropping history. Thoroughly mix the composite sample by gently breaking the soil cores.

At this point we advise splitting the composite sample in two: one for soil fertility and one for SCN testing. Place 1 pint (approx. 2 cups) of soil in a labeled plastic bag and ship it to the lab as soon as possible.

How should you handle your SCN soil sample?

Lopez-Nicora reminds producers that your soil sample is alive, therefore you must handle it carefully. To keep the nematodes alive, store your SCN samples in a cool, dark place out of direct exposure to sunlight and ship them to the lab as quickly as possible.

Where should you send your soil sample for analysis? There are several SCN testing labs in the North Central Region, however, with funding from the Ohio Soybean Council and The SCN Coalition, growers may submit up to two soil samples to his lab, and he will test them for SCN free of charge.

OSU Specialists suggest collecting one composite sample from a low- and another from a high-yielding area, as this will allow them to determine whether SCN is the reason for low yield.

For more information on SCN and submitting samples stop by or contact the Clinton County Extension Office at (937) 382-0901 or email nye.1@osu.edu . We can provide you with a required submission form.

Producers may send samples direct to: OSU Nematology and Soybean Pathology Lab, Attn: Horacio Lopez-Nicora, Ph.D. 110 Kottman Hall, 2021 Coffey Rd., Columbus, Ohio 43210.

Tony Nye is the state coordinator for the Ohio State University Extension Small Farm Program and has been an OSU Extension Educator for agriculture and natural resources for over 30 years, currently serving Clinton County and the Miami Valley EERA.

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Tony Nye

OSU Extension