Effects of some herbicides on non-target soilborne bacteria and fungi

In this study, it was aimed to determine the effects of herbicide active ingredients fluazifop-p-butyl, metribuzin and pendimethalin on beneficial bacteria Pseudomonas putida and Bacillus cereus, harmful fungi Rhizoctonia solani, Fusarium oxysporum f. sp. lycopersici, Phytophthora capsici and Sclerotinia sclerotiorum and beneficial fungi Trichoderma harzianum in the soil pathogen pool of agricultural fields. The study was conducted under in vitro, greenhouse and field conditions. Increasing doses of fluazifop-p-buthyl, metribuzin and pendimethalin to B. cereus and P. putida were found significant under in vitro conditions. Moreover, increasing doses of pendimethalin, fluazifop-p-buthyl significantly reduced the concentration of both bacteria. On the other hand, increasing doses of pendimethalin decreased the concentration of P. putida, but did not affect the concentration of B. cereus. In the greenhouse, the concentration of B. cereus increased with increasing doses of pendimethalin. As the doses of active substances increased in the greenhouse, the concentration of P. putida bacteria also increased. In the field, the recommended doses of pendimethalin and metribuzin did not inhibit B. cereus concentration, while the dose of fluazifop-p-buthyl increased bacterial concentration. Herbicide active substances inhibited the growth of S. sclerotiorum in vitro but had no effect under greenhouse conditions. Herbicide active substances reduced the growth of T. harzianum under in vitro, greenhouse and field conditions, but the value of T. harzianum was never zero in soil. Herbicides inhibited R. solani growth at all doses under in vitro conditions, but only at increasing doses under greenhouse conditions. Pendimethalin inhibited P. capsici growth in vitro by 25%, fluazifop-p-buthyl by 80% and metribuzin by 100% at increasing doses. Under greenhouse conditions, increasing doses of herbicides reduced the growth of P. capsici. In the greenhouse and field, Metribuzin was phytotoxic to pepper plants and caused rapid spread of P. capsici. The active substances pendimethalin and Fluazifop-p-buthyl slowed down the growth of F. oxysporum f. sp. lycopersici under in vitro conditions and decreased with increasing doses. Fluazifop-p-buthyl reduced fungus growth in the greenhouse. Metribuzin reduced the growth of F. oxysporum f. sp. lycopersici fungus in vitro, greenhouse and field conditions. The results of the research revealed that the control of soilborne fungi and bacteria may vary according to the type of herbicide active substance, chemical structure and dose of the herbicide, soil structure, presence of microorganisms in the soil, light, irrigation and moisture content. The results of this study show that herbicides are effective on pathogenic fungi in the soil, but do not completely eliminate beneficial organisms.