According to the latest survey, both soybean cyst nematode (SCN) and root knot nematode (RKN) are leading causes of soybean yield losses in portions of the Midsouth. Thus, sampling for these pests is important on those sites (medium- and coarse-textured soils, fields with continuous soybeans [SCN]; sandy soils that have been cropped to corn and/or cotton [RKN]) that are likely to harbor populations of either or both of these species.
As stated in the Nematode White Paper on this website, the best time to sample for SCN is in the fall just after soybean harvest. However, if this was not done, sampling in the spring should still be done (Tonneson, Dakota Farmer, Mar. 2018). This is especially important in fields or portions of fields 1) that may have flooded during the winter, 2) that had significant waterfowl activity during the off-season, 3) that are known to have high pH, 4) where equipment entered a field, and 5) that had stunted areas that produced low yields during the previous soybean growing season. Analyses of collected samples should include a determination of the density and race or type of SCN present in individual fields so that varieties with the appropriate SCN resistance source can be selected for planting on infested sites.
As more soybean acres in the Midsouth are rotated with cotton and corn, it is now just as important to analyze samples from these fields for RKN presence. However, rotational management options for soybeans grown in fields infested with RKN are limited because corn, cotton, and soybean all serve as hosts for this species. Also, unlike the large number of SCN-resistant soybean varieties that are available, the number of varieties resistant to RKN is low in MG’s IV and V that are commonly planted in the Midsouth.
I encourage you to review all the nematode resources on this website to ensure that you are aware of potential nematode problems in your fields and are taking all possible precautions and applying remedial measures to avoid nematode-related yield losses when either or both of these nematodes are present.
Composed by Larry G. Heatherly, Mar. 2018, firstname.lastname@example.org