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Swede midge populations peak with hot weather

July 9, 2013, Ontario – High numbers of swede midge are being reported in many canola growing areas, including New Liskeard, Dufferin, Grey, and Wellington. Growers and agronomists need to take action immediately to protect canola that has not bolted and began to flower. Some growers and agronomists are already reporting significant damage. Swede midge can cause serious damage to canola, preventing bolting, distorted growth and in some cases over 50 per cent yield loss has occurred.

Midge adults emerged from overwintering sites earlier than in the past. Don’t expect to be able to see the midge. Adult midges are tiny, only one to three millimetres, and can only be monitored for by using Jackson insect trap. There are several overlapping generations of midge each year, so catches will rise, fall and rise again.

A map indicating swede midge trap catches can be found at Regularly check this website for updates on the level of swede midge in your growing area until your canola is beyond the vulnerable stage. While this map may not be indication of populations for your field, they do give an idea of when population peaks are occurring. Heat and rain  triggers Swede midge emergence.

Canola fields at risk
Canola prior to full flower is at risk of damage. Canola at the rosette stage will be at greatest risk. Many fields are in late rosette stage to bolting and still at very vulnerable stage for damage. The greatest damage and loss occurs when midge attack canola prior to bolting. If a field is uneven in growth or thin, protection from midge will be required longer. In thin stands, canola plants produce more side branches and these become more important to yield. Side branches won’t be fully developed until the main raceme is in full flower. Thin stands will need to be protected longer to allow these side branches to develop. Once flowering on secondary/tertiary branches is initiated economic loss from midge will be minimal. Swede midge populations are generally the highest in canola fields that are located in relatively close proximity to fields where canola was grown in the past but this is not always the case. Midge can overwinter in the soil for more than one season, emerge and migrate to nearby canola. Although swede midges are not strong fliers, they can also be moved on wind currents.

Product selection
This season we are conducting timing and product trials but we don’t have enough data or experience to give you the best control strategy.

The two approved products for treatment of swede midge in canola are Matador and Coragen. Matador is most effective on the adult midge, while Coragen is most effective on the larvae and egg stages and works to reduce activity of adults. Matador will control adult midge present in he field at time of application, but not subsequent migrations into a field. Coragen appears to
offer a somewhat extended residual effect (1 to 2 weeks). A maximum of 3 applications of Matador/Silencer are permitted per season. Although is tempting to use Matador because it is about ½ the cost of Coragen it is important to consider the stage of your canola, and populations and stage swede midge are at in your area. The best control will be achieved by properly time any spray to protect canola prior to seeing significant damage.

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July 9, 2013  By Ontario Canola Growers


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