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Manitoba Agriculture, Food and Rural Initiatives

Manitoba Insect and Disease Update

May 31, 2010                   

Compiled by: John Gavloski, Entomologist, Manitoba Agriculture, Food and Rural Initiatives
                    Phone: (204) 745-5668; Fax: (204) 745-5690, and
                    Vikram Bisht, Plant Pathologist, Manitoba Agriculture, Food and Rural Initiatives
                    Phone: (204) 745-0260; Fax: (204) 745-5690

To report observations on insects or plant pathogens that may be of interest or importance to farmers and agronomists in Manitoba, please send messages to the above contact address.

To be placed on an E-mail list so you will be notified immediately when new Manitoba Insect and Disease Updates are posted, please contact John Gavloski at the address or numbers listed above.


• Cutworms have been a concern in some fields
• Wheat streak mosaic continues to be found in some cereal crops.
• Diamondback moth counts continue to increase in traps in southern Manitoba.

Recent Insect Concerns and Observations

Cutworms: Cutworms continue to be a concern in some fields, particularly in the Central region of Manitoba. Insecticides have recently been applied to control cutworms in some corn fields and a potato field in the Carman area.

Caterpillars on canola: An interesting and unusual observation was reported by a Cargill agronomist from a field of canola near Winkler, where cankerworms were feeding on canola. Cankerworms do not normally feed on canola, but in this particular instance some very strong wings had blown cankerworms and debris from a shelterbelt into nearby canola. The cankerworms were feeding on the canola. Although unusual, it is something to consider if finding larvae other than those more typical on canola feeding on canola near a shelterbelt.

Cankerworms on Canola

Wheat Streak Mosaic: More fields have been testing positive for wheat streak mosaic. These fields are mainly in the Central and Southwest parts of Manitoba.


Surveys and Forecasts

Diamondback moth: Counts of adult diamondback moths continue to increase in pheromone-baited traps in several areas of Manitoba. Highest counts are from the Eastern part of Manitoba. Some of the higher counts after 3 weeks of trapping are 137 from a trap near Landmark, 84 from a trap near Carey, 78 from a trap near St. Jean Baptiste, 73 from traps near Altona and Arnaud, 65 from a trap near Kleefeld, and 51 from a trap near Dugald. Diamondback moths arrived early this year, so this is something to look for when scouting canola fields. Larvae are just starting to emerge, and will be quite small. It’s hard to predict what impact the heavy rains over the weekend may have on diamondback moth populations. Heavy rains can reduce levels of larvae. However, we are likely only at the beginning of egg hatch from those that blew in, and the first stage mine the leaves. So diamondback moth remains an important thing to look for when monitoring canola fields.

Data for the diamondback moth monitoring program is updated at the beginning of every week on the MAFRI website at: 2010 diamondback data

As an interesting observation, an armyworm moth was also found on our trap for diamondback moth in Carman this week. Armyworms are generalists and feed on a lot of crops, and are also an insect that arrives from the south. Note that this is different than the bertha armyworm, which is primarily a pest of canola. Note the white dot on the wing of the armyworm in the photo below; this was the specimen found on our diamondback moth trap.