Effects of soil applications of benomyl and captan on the growth of onions and the occurrence of endophytic mycorrhizas and rhizosphere microbes

SUMMARY When grown for 6 months in the absence of pathogens, repeated soil applications of benomyl or captan significantly and similarly decreased growth of onion seedlings by 22–25% (diameter) and 31–34% (dry weight). The losses were associated with differing effects on soil microbes. Whereas captan had no effect on the occurrence of vesicular‐arbuscular mycorrhizas it appreciably decreased populations of rhizosphere fungi. In contrast benomyl inhibited mycorrhiza formation but had a relatively small effect on rhizosphere fungi.