The in vitro effect of the herbicide Basta® (glufosinate ammonium) on potential fungal grapevine pathogens.

Glufosinate ammonium-based herbicides are commonly used in commercial vineyards to control excessive growth of weeds. However, glufosinate ammonium also seems to have antifungal properties. Since recent reports indicate fungicidal activities also to grape pathogens, several fungal organisms putatively pathogenic to grapevine (Botrytis cinerea, Guignardia bidwellii, Penicillium expansum, Phomopsis viticola) were exposed to glufosinate ammonium in an in vitro assay. The herbicidal compound caused reduction of mycelial growth in a dose dependent manner. G. bidwellii was the most sensitive pathogen, and mycelial growth was reduced about of 80 % when exposed to a 500fold diluted solution of glufosinate ammonium normally applied to the field. As an interesting side effect, glufosinate ammonium nearly inhibited spore production in Penicillium expansum cultures when exposed to the same low concentration. Even though fermentation of must by yeasts may be affected due to residues attached to grapes, spray applications of glufosinate ammonium to the ground leading to a dispersal of small amounts to non-treated areas could help to reduce the built-up of secondary inoculum in the same season or primary inoculum for the following year.