Wheat streak mosaic virus (WSMV) is showing up across Manitoba in winter wheat, according to the province's latest insect and disease update. WSMV is spread by wheat curl mites, and chemical controls are not available for the mites or the disease. Scout winter and spring wheat fields for this disease especially where these crops are grown side by side.
Recent cool weather has slowed flea beetle activity but not necessarily killed the insects. "We should soon be getting to the point where we will see the levels of adult flea beetles start to die and populations decline. But as we get into some warmer weather, make sure to monitor canola fields that may still be susceptible to feeding from flea beetles," the report says.
Regarding a rumour that striped flea beetles are resistant to the seed treatments used in canola, the report says there have currently been no confirmed cases, but there is some variability in the level of mortality that the neonicotinoid seed treatments can have on different species of flea beetles.
More feeding damage from seedcorn maggot has been noticed over the past week. Seed treatments that control seedcorn maggots are available, however rescue treatments after the crop has been seeded are not available. Seedcorn maggots can be a problem in many large seeded crops including corn, beans, peas, and soybeans.
High populations of aster leafhoppers continue to be found in cereal fields in Manitoba. Leafhoppers feed on plant sap, and aster leafhoppers can potentially spread a disease called aster yellows, which can affect field crops, such as cereals, flax, sunflowers and canola, however damage is usually not as severe as for horticultural crops such as carrots.
Growers of horticultural crops should monitor for aster leafhoppers in their crops, and some have already started to control aster leafhoppers in or near their crops.
High populations of cutworms continue to be noticed in some fields. The report reminds that cutworms are nocturnal, and will be under the soil or debris during the day and emerge to feed at night. So if fields do need to be treated for cutworms, spraying as late in the day as possible is advised. Cutworm populations can also be very patchy in fields, and sometimes only a portion of a field may need to be treated.
MAFRI entomologist John Gavloski asks producers to John.Gavloski@gov.mb.ca%22">let him know as soon as possible if they see high populations of cutworms. Someone will come to the field to collect cutworms for a research project on parasitoids of cutworms.
Diamondback moths were found in pheromone-baited trap early in 2012. Traps around Morris and Beausejour have had the highest counts, and all the higher counts continue to be in the eastern part of Manitoba. West of Carman the counts have all been low.
-- Information provided by MAFRI entomologist John Gavloski and plant pathologist Holly Derksen. Full text and photos are available online.