Little is known about the effects of herbicides on soil-borne pathogens of the common bean. The effects of herbicides on the mycelial growth of Fusarium solani f. sp. phaseoli, F. oxysporum f. sp. phaseoli, Macrophomina phaseolina, Rhizoctonia solani, Sclerotium rolfsii and Sclerotinia sclerotiorum were evaluated. These soil-borne fungi cause the most devastating diseases on the common bean. Radial mycelial growth of these fungi was evaluated on potato dextrose agar medium in Petri dishes at five concentrations (0, 1, 10, 100, 1,000 mg L-1) of the herbicides imazamox, fomesafen, fluazifop-p-butyl, bentazon, glyphosate, and S-metolachlor. Mycelial growth of all fungi decreased sharply only with S-metolachlor at 1,000 mg L-1. Thus, the effect of S-metolachlor, at two concentrations (1,000 or 12,000 mg L-1), was evaluated on germination of sclerotia of S. rolfsi and S. sclerotiorum (myceliogenic) or S. sclerotiorum (carpogenic). S-metolachlor did not affect significantly the myceliogenic germination of sclerotia of these two fungi. However, S-metolachlor delayed carpogenic germination of sclerotia of S. sclerotiorum. Our results suggest that the herbicide S-metolachlor has potential to be used for integrated management of common bean diseases caused by soil-borne fungi.
Phaseolus vulgaris; integrated management; mycelial growth; sclerotia
