Suspicious Bud Bouqueting – Thrips to Blame?

A number of reports of ‘bud bouqueting’ were received from fields in southern and central Alberta where flower clusters develop in the centre of the rosette without bolting. The internodes on the primary branch are shortened and, as a result, the buds appear within the centre of the rosette. A number of factors can cause shortened internodes (e.g. environmental stress, chemical damage, insects (such as thrips). If bud bouqueting is noticed, the following scouting tips may help uncover the cause:

• Scout the field thoroughly. Pay close attention along the field edge and corners where the sprayer boom may have swung wide as this may have resulted in an untreated area. If the symptoms do not appear in the unsprayed area, then perhaps chemical damage is playing a role.
• Pull plants and examine the root system. Perhaps something below the soil surface is causing the symptoms.
• Make note of any pattern of affected plants within the field. Are low areas more affected than knolls or vice versa? This can often help determine if symptoms are temperature related.
• Scout for thrips. The Entomology Department at the University of Alberta positively identified thrips to be the cause of bud bouqueting in a field near Morinville, Alberta. Pull complete plants and using a piece of paper (often useful to use a white and a colored piece) beat the plant gently on the paper on a hard surface to dislodge any insects that may be hiding within the buds. Thrips are very small (adults 1 mm in length) so a magnifying glass may help.
• Anyone noticing symptoms of bud bouqueting can contact their regional agronomist (contact information below) for further assistance.

A photo of a thrip is available at the Canola Council of Canada’s photo gallery at the following link: http://www.canola-council.org/gallery/855/pests_insects.aspx.