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SCN Biology and Management (Iowa State University)

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This following sets were initially created as part of the SCN Coalition.

Biology of the Soybean Cyst Nematode

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Symptoms and Soil Sampling

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Soybean Cyst Nematode Management

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Recommended technique: Collect soil samples and have the SCN population densities determined.

When to sample
You can take a soil sample to check on the progress of a SCN management plan at almost any time of the year. But if you want to monitor the effectiveness of your SCN management program over several years, you should sample at the same point in the management program each time (say after a year of resistant soybeans or nonhost crop).

Generally avoid sampling frozen or saturated soil since these samples are harder to process and that may affect the accuracy of the results obtained. Fall is often the best time to sample as you plan for the next crop year.

Recommended technique: Collect soil samples and have them tested for the presence of SCN.

When to sample
Fall is often the best time to sample as you review harvest data. Take samples from the harvested soybean field, either in a zig-zag pattern or as part of a grid sample, as described below.

How to sample
The equipment you need for sampling soil for SCN is the same equipment you use for taking a soil sample for soil nutrient analysis: a soil probe, a bucket, and a plastic or plastic-lined soil bag. Sample the top 6 to 8 inches of soil.

Recommended technique: Collect soil samples and have them tested for the presence of SCN.

When to sample
Fall is often the best time to sample as you plan for the next crop year. Sample as described below in the harvested field that is to be planted with soybeans next season.

  Soil samples can be collected throughout the fall, until a significant snowfall or a hard freeze occurs.  

Bulk the cores in a container and mix thoroughly. Take the time to mix the sample. The better the sample is mixed the better it represents the whole field.

Place the root samples in separate 100 or 150 ml glass beakers. Prepare 600 ml of a water-bleach solution by adding 100 ml household bleach (5% sodium hypochlorite or NaClO) to 500 ml distilled water. Add about 50 ml of water-bleach solution to each beaker containing a root sample.

Incubate roots in the water-bleach solution for 4 minutes, stirring with a metal spatula periodically. Rinse roots for 45 seconds or so in running tap water, then soak the roots in tap water for 15 minutes.

To prepare the disinfestant solution of 0.5% chlorhexidine diacetate (Hibitane), dissolve 0.5 g into 100 ml sterile distilled water, or dissolve 2.5 g into 500 ml sterile distilled water

To disinfest the eggs:

Construct microsieves from 18-mm and 20-mm test tube caps and 25 micrometer pore nylon mesh.
UV-sterilize all microsieves and hatch trays.

Arrange the hatching trays in replicated boxes using a pre-generated random order. Fill each hatching tray with 12 ml of the appropriate test or control solution.

Pipette between 5,000 and 10,000 surface-disinfested SCN eggs (depending on experimental details) onto each microsieve.

Incubate the experiment at room temperature in darkness. At every-other day intervals, transfer the microsieves to duplicate hatching trays containing fresh solution, and count the hatched SCN second-stage juveniles remaining in the original solution.

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.