Bud Bouqueting – Thrips to Blame? Send Samples for ID

Reports continued this past week of  bud bouqueting — where flower clusters develop in the centre of the rosette without bolting — from fields in southern, central and Peace Region of Alberta. 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 growers notice bud bouqueting, the following scouting tips may help discover 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 there is something below the soil surface that 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.
• Thrips were believed to be the cause of symptoms in one field near Morinville, Alberta. To scout for thrips pull complete plants and using a piece of paper (often useful to use a white and a colored piece) bang the plants 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. If thrips are found, it is important to have a positive species identification made because some species (e.g. pollen feeders) have been found to increase pollination and others have resulted in yield reductions (feeding during bud stage).
• Ken Fry at Olds College will accept insect samples for thrip species identification. Insect samples can be obtained by banging a flower cluster inside a plastic cup and then emptying the contents into a leak-proof vial with a suitable preservative (rubbing or isopropyl alcohol, RV anti-freeze, ethanol).  Send these labeled vials in a crush proof package to: Ken Fry, Olds College, 4500-50th Street, Olds, AB  T4H 1R6
• Anyone noticing symptoms of bud bouqueting can also 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.