Parasitism of the Nematode Heterodera glycinesby the Fungus Hirsutella rhossiliensisas Influenced by Crop Sequence
Keywords:
biological control, corn, crop rotation, crop sequence, glycine max, heterodera glycines, hirsutella rhossiliensis, nematode, nematophagous fungus, soybean, soybean cyst nematode, zea maysAbstract
The effect of crop sequence on parasitism of second-stage juveniles (J2) of Heterodera glycines by Hirsutella rhossiliensis was investigated. Data were collected from plots of a long-term crop rotation experiment established in 1982. Crop sequences included (i) continuous monoculture of corn and soybean; (ii) annual rotation of the two crops; and (iii) 1, 2, 3, 4, or 5 years of each crop following 5 years of the other crop. The nematode J2 density and percentage of J2 parasitized by the fungus were determined at planting, midseason, and end of season in 1997 and 1998. A significant effect of the crop sequence on parasitism of J2 was observed at midseason in both years and at end of season in 1998. In plots of first-year soybean following 5 years of corn, fungal parasitism increased from an undetectable level at planting to 2% and 4% of J2 parasitized by ends of season in 1997 and 1998, respectively. Fungal parasitism was similar in plots of second-through-fifth-year soybean after 5 years of corn and in plots of soybean monoculture. Parasitism of J2 in the soybean plots in annual rotation with corn increased from undetectable and 2% at planting to 6% and 23% at midseason in 1997 and 1998, respectively. The effect of crop sequence on the fungal parasitism of J2 may be attributed to a density-dependent relationship between the parasite and its host. Season also affected the fungal parasitism; percentage of J2 parasitized by the fungus was the highest at midseason and the lowest at planting.Downloads
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