Manitoba Agriculture’s weekly Insect and Disease Update says that stripe rust has been identified near Brandon. MAFRI pathologist Holly Derksen confirmed the "low-severity" infection as a late addendum to the report.
"I could only find one plant showing symptoms. This pathogen slows down under hot, dry conditions, so a foliar fungicide application was not recommended for that field at this time," she said.
The update said stripe rust has been observed in spring and winter wheat in Minnesota and North Dakota. Severe infection on spring wheat near Langdon, North Dakota have been reported.
Other highlights from the report:
• Crown rust in oats in Minnesota has been reported in Renville county in the southern part of the state, west of Minneapolis. This is the first reported case in Minnesota and there have not been any reported cases in North Dakota yet this season.
• Although there have not been any observations of cereal rusts in Manitoba, reports from North Dakota and Minnesota indicate that they are “knocking on our door.” Derksen asks for reports of any cases (pictures are appreciated).t
• Diamondback moth populations seem to have declined in some areas, and plants are getting to the stage where they can tolerate more feeding. We may be in between generations as well in some areas.
One of the inquiries this week was about tank-mixing an insecticide with their fungicide application to get early control on diamondback moth. In the update, entomologist John Gavloski lists several reasons why this is not advisable.
• Reports of heavy feeding on alfalfa by alfalfa weevil have been coming in from across Manitoba. Some of the heaviest feeding seems to be in the western part of the province.
• Thistle caterpillar: Some have been noticing thistle caterpillars on soybean and sunflowers. One of their favorite hosts is thistles, and they will often preferentially go to thistle plants. When these are not abundant, or have been controlled, they will feed on crops like sunflowers and soybeans. So far the feeding has been minor, and some of the caterpillars are getting quite big. They eventually become a butterfly known as the painted lady butterfly.
• Bertha armymorm: Some higher counts of moths are starting to be found in the pheromone-baited traps. The update reports trap counts and thresholds for damage assessment.
• Dr. Martin Erlandson with Agriculture and Agri-Food Canada is studying the genetic diversity of bertha armyworms and is asking for volunteers to send in the dead bertha armyworm moths — contact details in the full update.