Effect of "Cotton Complex" Nematodes on Seed Yields of Soybean

Field experiments were conducted for 3 years to assess vield loss to a mixture of lance (Hoplolaimus galeatus), lesion (Pratylenchus spp.), stubby-root (Paratrichodorus christiei), and spiral nematodes (Helicotylenchus dihystera) in 7 soybean cultivars. Yield loss was assessed by comparing control plots with plots that received a planting-time application of 18.7 L EDB/ha. In the first year nematodes reduced yield by 24% with no effect on above-ground appearance of plants. Fumigation also influenced nematode numbers the first year, but cultivars did not. Yield loss from nematodes was slightly less during the next 2 years (14% and 13%). Cultivars affected nematode numbers only in one of 3 years. We concluded that this particular nematode complex was capable of causing significant yield loss, and that genetic variability among the cultivars tested for reaction to individual nematode species was minimal.