Thursday, 14 July 2016

Weekly Update (July 13, 2016; Wk 11) - Swede midge

Swede midge (Contarinia nasturtii)  - Pheromone traps captured the first swede midge of 2016 between May 25 and 31 in northeastern Saskatchewan.  This is substantially earlier (6-7 weeks) compared to 2014 and 2015. 

Emergence traps indicate high numbers of swede midge have emerged in northeastern Saskatchewan. Producers should monitor their canola fields for damage symptoms. We are currently unaware of the consequences the heavy rain this week will have on population numbers, but will continue to update the PPMN as results become available.

Figure 1. Swede midge infested canola buds which are enlarged with sepals fused together. 

Figure 2.  Swede midge large (~1mm long; yellowish-white) feeding within canola flower.

Swede midge scouting tips for in-field monitoring:

• Watch for unusual plant structures and plant discolourations then follow-up by closely scrutinizing the plant for larvae.
• The growing tip may become distorted and produce several growing tips or none at all, young leaves may become swollen, crinkled or crumpled and brown scarring caused by larval feeding may be seen on the leaf petioles and stems.
• Flowers may fail to open.
• Young plants that show unusual growth habits should be examined carefully for damage and larvae; especially if the sticky liners have many flies resembling midges (swede midges are about the size of orange blossom wheat midge but are not orange).
• Larvae can be seen with a hand lens.
• Refer to the Canola Watch article by Dr. Julie Soroka for more information on swede midge and watch for a new Ontario fact sheet produced by Baute et al. 2016.