Canola Watch had a question this week about light-coloured petals and what can cause them.
The field in question had large unruly patches of light-coloured flowers, indicating it was likely related to soil. (See the drone image below.) Sulphur deficiency seems the most obvious, as pale-coloured flowers are a common symptom of a sulphur shortage.
To help with the sulphur diagnosis, also look at petal size and plant conditions. With sulphur deficiency, petals are pale AND small, and foliage symptoms — including cupped and shrunken new leaves — would be present if deficiency was enough to affect flowers.
Other potential causes are:
(1) Herbicide drift damage, but this symptom tends to show up at field edges or along the path of an inversion cloud.
(2) Glyphosate applied to RR canola at an excessive rate or late, but this would be most obvious in overlap areas.
(3) Variety off-types, but these would be lower in number and show up as randomly distributed individual plants throughout a field. Variety off-types with white flowers would also have normal sized petals, whereas sulphur-deficient pale flowers would have small petals.
The Canola Diagnostic Tool can help work through possible causes for any symptoms found in a canola field.
If sulphur deficiency is the cause, top dress fertilizer applications as late as early flower can improve yield. Read more.