EFFECTS OF A MUTANT STRAIN AND A WILD-TYPE STRAIN OF VERTICILLIUM-IECANII ON HETERODERA-GLYCINES POPULATIONS IN THE GREENHOUSE

A wild type strain of Verticillium lecanii and a mutant strain with in creased tolerance to the fungicide benomyl were evaluated in greenhous e experiments for effects on Heterodera glycines populations. Nematode s were applied at 300 eggs and juveniles per 4,550-cm(3) pot (two soyb ean plants in 4,990 g loamy sand per pot) and at both 300 and 10,000 e ggs and juveniles per 1,720-cm(3) pot (one soybean plant in 2,060 g sa nd per pot). With 300 nematodes added per pot, both V. lecanii strains significantly reduced nematode populations in loamy sand (fungus appl ied at 0.02% dry weight per dry weight loamy sand) and sand (0.006% an d 0.06% fungus application rates). The mutant strain applied at 0.002% to sand also significantly reduced cyst numbers. When 10,000 nematode s were added per pot, only the mutant strain at 0.06% significantly de creased population. Various media were tested for isolation of the fun gus strains from prills, loamy sand, and sand, but the fungi,were reco vered from few of the greenhouse pots.