Abstract
Incidences of soil fungi were recorded for 1 cm3 volumes of untreated and fumigated nursery soils using new selective isolation media. In July, 10 months after application of Trizone at 1 lb/100 ft2, there were many viable Pythium propagules in the treated surface soil (11/cm3) but significantly fewer than in nonfumigated soil (29/cm3). Studies with baits showed that Rhizoctonia and Fusarium spp. were also present in both soils. The total number of fungi in fumigated soil (11,000) was lower than in nonfumigated soil (30,000). Trichoderma propagules were very common and significantly more so in fumigated (1,120) than in nonfumigated (270) soil. The same held for bacteria (10 million vs. 7 million). Reinfestation with four potentially pathogenic genera of fungi was found to take place by means of splashing rain and irrigation water, dust, and soil carried by man.