IMPROVED CHEMICAL CONTROL OF BOTRYTIS BLIGHT IN ROSES

Botrytis cinerea causes latent infections of rose flowers, which can d evelop into aggressive rot (botrytis blight) at pre- and postharvest s tages. Botrytis blight is the cause of major rose flower losses. The e ffect of deposit and cover density of fungicides (pyrimethanil or proc hloraz-Zn - folpet) on the development of botrytis blight was tested. For pyrimethanil drop size and cover density (ranging between 80 and 1 000 mu m drops/cm(2)) had no effect on disease rate, if the pesticide deposit was sufficient for disease control. For prochloraz-Zn folpet, however, control efficacy (for equal deposit) increased with cover den sity. Secondary distribution of pyrimethanil was by the vapor phase. E ffective control was obtained when rose petals were exposed only to py rimethanil vapors, while any direct contact with the fungicide was pre vented; no control was recorded for prochloraz-Zn - folpet under these conditions. Botrytis blight was delayed in cut flowers when bunches o f 20 flowers were wrapped in packing paper strips or cellophane bags w hich had been sprayed previously with pyrimethanil and packed (20 bunc hes) in cardboard boxes. No pesticide stains could be seen on the flow ers.