Flowers and VOC's
Much is said about Oil seed rape crops when they are in flower, possibly because they are so striking to the eye or maybe it’s the distinctness of the scent they produce.
It is though that a short flowering period (less than 28 days) is best for crop and yield alike. This year some crops may be flowering for 56 days. There are many reasons for this.
Pollen grains are quite large (flowers are mostly insect pollinated so only a small amount of pollen is airborne) and so pollen does not affect allergy sufferers greatly. However, the smell is quite distinctive and travels some distance. What can trigger uncomfortable symptoms in those who are sensitive to such things are the volatile organic compounds (VOCs), such as terpenes, which the plant produces when in flower.
These VOCs do become airborne, so they can be inhaled. The characteristic odour of oilseed rape comes from the release of these VOCs. The quantity and strength of the emissions is influenced by environmental factors such as light levels, humidity, time of day and temperature.
So what now. Well the early flowers have set and small pods are forming. This triggers the potential for another disease to become problematic, that of Sclerotinia.
For this disease to affect yield at a commercial level weather conditions must be right so for the present its still best to concentrate your attention on Light leaf spot.