INFO-BUG

Crop Selected: Soybean
Crop Development: Bloom to pod-set
Pest Selected: Soybean Cyst Nematode, Heterodera glycines

Biology

Soybean cyst nematode is a relatively new pest problem affecting soybeans in Ohio having been found on soybeans for the first time in Ohio in 1987. Based on a survey conducted from 1992 through 1995, SCN has been found in 43 of 63 counties surveyed (primarily soybean growing counties).

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SCN is a microscopic (1/64 inch long) roundworm that feeds on feeds on soybean roots. The cyst stage is the body of the dead, mature female nematode filled with eggs. This cyst in highly resistant to adverse conditions and serves to protect the eggs and young nematode larvae for many years.

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SCN Life Cycle Cyst on soybean roots SCN Cysts Cyst on soybean roots SCN Cysts

Assessment:

SCN causes reduced yield and can cause patches of stunted and yellowed plants. Before implementing control measures, soil from suspect fields should be sampled and analyzed for presence of SCN. Females may be seen on soybean roots in July and August. Identification of the nematode at other times requires identification of cysts and/or larvae in soil samples or by bioassay of infested soil.

Nematodes will not be uniformly distributed in the soil. Sub-samples of soil taken from several sites in an infested field need to be combined into a composite sample for laboratory examination.

Using a 1-inch diameter soil probe or a shovel, take 15-20 sub-samples in a zig-zag pattern in a one acre area from a 10 acre section. Mix the soil thoroughly and place 1 qt in a plastic bag for shipment to a diagnostic laboratory assay.

Control

When SCN is detected in an area, control procedures should be instituted immediately. No single method will completely control SCN once it is introduced into the field. In most cases, a combination of disease control practices will be required to reduce losses from SCN damage.

1). Prevent Introduction: This is the first line of defense. Nematodes can move no more than a few inches per year in soil by their own effort. Anything that moves soil will transport the nematode.

2). Rotate Crops: Rotating soybeans with non-host crops (corn, small grains, alfalfa) may be the most effective method of controlling SCN.

3). Use Resistant Varieties: Some resistant varieties are available for Ohio growing conditions. Use where populations are low to prevent population buildup or after crop rotation to lower populations.

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