Effects of mycofumigation using Muscodor albus and Muscodor roseus on diseases of sugar beet and chrysanthemum
Methyl bromide-chloropicrin mixtures are the major chemicals used for soil disinfestation in the U.S. These chemicals are highly efficacious fumigants used for preplant soil fumigation in field and greenhouse production. They control soil-borne diseases, insects, nematodes and weeds. The 1996 International agreement to phase-out methyl bromide for soil fumigation will seriously reduce options for controlling soilborne pathogens. Mycofumigation is the use of antimicrobial volatiles produced by fungi such as Muscodor albus and Muscodor roseus for the control of other microorganisms. A synthetic mixture of organic components, which were originally identified in M. albus gases, provided disease control equal to the formulated fungus in terms of reducing damping-off by Aphanomyces cochlioides, Pythium ultimum, and Rhizoctonia solani. The effect of growth substrates for M. albus and M. roseus, their placement and fumigation period on efficacy for control of sugar beet seedling diseases was studied. Optimal growth substrates for M. albus were barley, canola, oat, and stabileze while optimal growth substrates for M. roseus were oat and barley. A 1-week mycofumigation period provided better control of damping-off than direct planting for both Muscodor sp. Mixing substrates with soil was superior to placement in the upper 25 % of the pot in Rhizoctonia-infested soil, whereas placement the in the upper 25 % of the pot was superior in Aphanomyces- and Pythium-infested soil. Field experiments indicate that mycofumigation of Aphanomyces-infested soil, buried 20 and 30 cm deep in field soil, increased seedling establishment of sugar beets. A winter survival study confirmed that M. albus does not survive the winter when buried (0 to 45 cm) in field soil in Montana. Storage of Muscodor sp. stabileze in a starch /sucrose / silica formulation was effective at - 10 °C and 3 to 5 °C for 5 months. In chrysanthemum experiments mycofumigation with M. albus and M. roseus resulted in significantly decreased Verticillium stem colonization compared to the V. dahliae pathogen control.