Temperatures are usually lower at early flowering in winter oilseed rape than later in the season and this influences the persistence of flowers. Individual flowers may last for 10 days at early flowering and less than 3 days at mid to late flowering. The number of open flowers tends to increase cumulatively up to mid flowering when about 20 flowers have opened on the main raceme. The numbers of falling petals (and hence the risk of sclerotinia infection) increases from the mid-flowering stage. This almost certainly explains why early to mid-flowering fungicide timings are particularly effective for sclerotinia control.