Description:
Soil in Field 2 at the USDA Forest Service Nursery,
Coeur d'Alene, Idaho was assayed six times over a 2-
year fallow period for potentially pathogenic Fusarium
and Pythium spp. following incorporation of a corn
cover/green manure crop. Populations of potentially
disease-antagonistic Trichoderma spp. were also
assayed. Soil populations of Fusarium did not decrease
over the fallow period and were at sufficient levels
after two years to be of concern from a disease
potential standpoint. Populations of Pythium were
fairly low throughout the monitoring period.
Trichoderma populations remained high, but were
probably not sufficient to ameliorate Fusarium disease
potential. Fusarium spp. readily colonized soil organic
matter particularly roots of the previous conifer
seedling crop; these fungi also frequently colonized
corn organic debris. Fusarium oxysporum was the
major potential pathogen colonizing soil and organic
matter. When a corn cover/green manure crop is
produced within fields destined for conifer seedling
production, these fields will require soil fumigation
prior to sowing seedling crops to reduce risk of
Fusarium-associated diseases.