Effects of Ampropylfos (RS)‐1‐aminopropylphosphonic acid) on zoospore formation, repeated zoospore emergence and oospore formation in Aphanomyces spp.

Abstract The effects on growth, asexual and sexual reproduction of different Aphanomyces species by the new fungicide ampropylfos ((RS)‐1‐aminopropylphosphonic acid) were tested using highly synchronized cultures. Ampropylfos reduced mycelial growth in Aphanomyces astaci, A. euteiches and A. stellatus. The fungicide was found to reduce zoospore numbers in all Aphanomyces species tested except A. euteiches. In one species, A. stellatus, zoospore production was inhibited at much lower fungicide concentrations than in the other species tested. In the pea pathogen A. euteiches, ampropylfos reduced the number of oospores, whereas the fungicide had little effect on asexual reproduction.