Sample Dry Edible Beans for Soybean Cyst Nematode (09/08/21)
We recommend that dry edible bean growers soil sample their fields for soybean cyst nematode (SCN). This is particularly important in Southeastern and East Central North Dakota, where SCN is most commonly found in the state.
Like soybeans, dry edible beans are susceptible to SCN. Also like soybeans, above-ground symptoms of infected dry edible beans are not diagnostic for SCN. Infected dry edible beans may only appear stunted, yellowed and have poor canopy closure (Figure 1). SCN can be observed on the roots, but as plants age it is increasingly difficult to identify (Figure 2). Consequently, soil sampling is the best way to test for the nematode.
Methods to sample dry edible bean fields for SCN are the same as soybeans. Sampling can be done anytime now until freeze-up. Using a soil probe (or shovel), take 10-20 subsamples per field, 6-8 inches deep, aiming for the roots. Mix the sample and submit to a lab. If you do not know if you have SCN, sample area where SCN is most likely to be first introduced such as field entrances (on equipment with soil), periodically flooded areas (with flood water) or near shelter belts (dispersed with blowing soil). Sampling high pH soils is also a good area to sample, as high pH favors SCN reproduction. If you already know you have SCN, understanding your egg levels will help you make management decisions next year.
Research conducted at NDSU demonstrated that different market classes of dry beans have different susceptibility to SCN. SCN was able to feed and reproduce on kidneys beans just as successfully as a susceptible soybean. SCN was able to feed and reproduce on pinto and navy beans, but at a reduced rate when compared to susceptible soybeans. Among all the market classes tested, feeding and reproduction was lowest on black beans. It is notable however, that differences among varieties within the market classes exist. If we were to use a soybean scale to compare the market classes, results would suggest that Kidneys would be rated ‘S’, pintos and navys ‘S/MS/MR”, and blacks ‘MR’.
Extension Plant Pathologist, Broad-leaf Crops