Effect of the herbicide fluazifop-butyl on fungal populations and activity in soil

The side effects of fluazifop-butyl on soil fungal populations and oxygen uptake were studied by incubating soil samples with a range of fluazifop-butyl concentrations (0, 0.6, 3 and 6 mu g g(-1)) over 8 weeks. Cellulose decomposition in soil was also studied in laboratory experiments with the herbicide which was either incorporated in soil or sprayed onto calico squares which were buried in soil. The mycelial dry weight of six fungal species under the effect of the herbicide was also examined. Fluazifop-butyl had no significant effect on total fungal propagule populations at 0.6 mu g g(-1). At 3 and 6 mu g g(-1),it caused temporary reduction in fungal populations observed after 1 and 2-wk of incubation. The herbicide had no significant effect on O-2 uptake. The decay of calico buried in herbicide-treated soil was generally stimulated, while the decomposition of herbicide-treated calico, buried in untreated soil, was temporary delayed. The mycelial dry weight yields of Aspergillus flavus (at 2 and 12 mu g mL(-1) of fluazifop-butyl) and Cunninghamella echinulata (at 12 mu g mL(-1)) were significantly increased. At 24 mu g mL(-1) the mycelial dry weight of A. flavus and Alternaria alternata was significantly reduced.