Blackleg is widespread in southern Manitoba. Disease severity on infected plants is still low right now, but severity can increase dramatically with hot weather. This level of infection is unusual to see at this stage. Growers with infected fields should be prepared for some yield losses. Staging is too late for protective spray, but scout fields for damage and plan to rotate those fields out of canola for a few years.
Alternaria is showing up in B. juncea canola. This is early and could cause some serious yield losses. Start scouting now, looking for lesions on the stem. It will move up the plant and eventually get to the pods, as shown in the photo below. The best staging for alternaria control is listed as 90% petal fall/late flowering to early green pod stage. Pre-harvest intervals vary from 7 to 30 days. Juncea, like Polish, is more susceptible than napus because it has less of a waxy barrier than napus.
Light stands encourage some growers to consider straight combining. To swath these stands would mean a higher risk for swath blowing, and some crops just don’t have the stalk counts to hold up a windrow. But straight combining has its own risks when plants whip against each other in the wind. Click here to read the CCC factsheet “Straight Combining Success Depends on Many Variables.”
Tank mix when spraying out poor canola fields. Some growers with very poor canola crops want to cut their losses and set up crop management plans for next year. The photo below shows one such field around Melfort, Sask. When spraying out a canola field, consider adding a broadleaf control component to the glyphosate application — even if the field is not an RR variety. This will control all canola, regardless of the system.
—Diamondback moth larvae scouting and spraying continues this week. Action threshold at the podding stage is 20 to 30 larvae per 1/10 of a square metre — or roughly one square foot. Click here for the diamondback moth report from last week.
—Lygus bug numbers are at thresholds in parts of the Peace and rising in Manitoba’s northwest. Even a field near Canwood, Sask. was sprayed for lygus this week. See the Tables 2 and 3 below for thresholds.
—Bertha armyworm numbers are nearing threshold in the La Crete area of the Peace, around Regina and Moose Jaw. Continue to scout as the area affected is likely larger than original reports indicate. See Table 1 below for thresholds.
—When a crop has more than one insect species feeding on flowers, buds and pods at the same time, consider the “additive” effect when assessing thresholds. For example, if you have diamondback moth and cabbage seedpod weevil in the same field and if both are at 50% to 60% of their economic spray thresholds, spraying may provide an economic benefit — especially if the crop is already stressed.