Experiments with fungicide sprays in late summer and early autumn on sugar‐beet root crops

SUMMARY Fentinhydroxide and benomyl sprayed on to sugar‐beet root crops in July, August and September frequently increased yield of tops. Sugar yield was increased only if either powdery mildew or virus yellows was prevalent, when on average a single fentinhydroxide spray at 0·7 kg a.i./ha increased sugar yield by 8% and yield of tops by 13%. The mildew specific fungicide fluotrimazole also increased yield, but it could not be determined whether this was due to controlling powdery mildew or secondary parasitic fungi attacking yellows‐infected plants. Repeated sprays of both fentinhydroxide and fluotrimazole, but not benomyl, appeared to be phytotoxic when applied in hot dry weather.