EFFECTS OF FUMIGATION AND OTHER SOIL TREATMENTS IN TEH GREENHOUSE ON THE FUNGUS POPULATION OF OF OLD CITURS SOIL

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Abstract
A study was made of the effects of various fumigants, fungicides, insecticides, leaching treatments, and steam under pressure on the fungus population of the soil. The expts. were carried out in the greenhouse using 3-gallon pots. Approx. 1 month after treatment orange seedlings or tomatoes were planted in the soil. The treatments reduced or destroyed the fungus population of the soil. Later the fungi re-established themselves. The kinds and numbers varied greatly between treatments and between replicate pots of the same treatment and usually represented few spp. in comparison with the untreated controls. Aspergillus versicolor, Fusarium oxysporum, F. solani Mucor spp., Penicillia, Penicillium nigricans, P. restrictum, Penicillium sp. 1, Pyrenochaeta sp., and Trichoderma lignorum commonly became dominant spp. One or more of 24 spp. occasionally became dominant. Some of these were present in relatively large concn. in the original soil, some in small concn., and others were found rarely or not at all. Sometimes the first spp. to become established after treatment remained dominant for the duration of the expt. In other soils a succession of forms occurred. For destroying the fungi and altering the nature of the subsequent population, steam under pressure or treatment with chloropicrin, D-D, 2% H2SO4, or 2% KOH were more effective than treatment with CS2, ethylene dichloride, ethylene dibromide, Dithane, or hexachlorocyclohexane.