Manitoba Insect and Disease Update: May 21, 2013

Compiled by:
  • John Gavloski, Entomologist
    Manitoba Agriculture, Food and Rural Initiatives
    Phone: (204) 745-5668
    Fax: (204) 745-5690.
  • Holly Derksen, Plant Pathologist
    Manitoba Agriculture, Food and Rural Initiatives
    Phone: (204) 750-4248
    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.

Recent Insect and Plant Pathogen Activity


Wheat Streak Mosaic Virus: Questions are coming in about planting spring wheat in a field where the winter wheat was torn up due to poor emergence or winterkill. The main disease consideration in this situation is Wheat Streak Mosaic Virus (WSMV). This disease is vectored by the wheat curl mite and both the virus and the mite can overwinter here on a living host, such as winter wheat. The main way this disease is managed is by breaking the “green bridge”. This concept refers to having a period of time (ideally two weeks) where there is no green wheat tissue available for the mite and virus to survive on. In the fall, this means there should be two weeks from the time the spring wheat ripened to when the winter wheat emerges. When understanding your risk for WSMV this spring think back to what conditions were like last fall:  Is your winter wheat bordering a spring wheat field from last year? Is there a chance that the “green bridge” was not broken? Chances are if you’re tearing up your winter wheat stand because it didn’t emerge last fall, your risk of WSMV overwintering in that crop is slim. That being said, be sure to thoroughly scout your crops, especially along field edges, for WSMV symptoms (see picture below). If there is a concern of WSMV, the green bridge can be broken this spring by ensuring two weeks between destroying winter wheat and emergence of this year’s spring wheat crop.


Image of Wheat Streak Mosaic Virus
Figure 1. Characteristic symptoms of Wheat Streak Mosaic Virus.







One of the focuses at this year’s Crop Diagnostic School will be diseases in alfalfa. It’s always preferable to be able to show live plants with disease symptoms, but we aren’t always “lucky” enough to have these diseases show up in our demonstration plots. Please contact myself ( or Glenn Friesen ( if you come across any disease issues in your alfalfa stands this year. We are not picky and are hoping to show foliar diseases (leaf spots, stem blights, etc.) as well as root/crown diseases which may be showing up as poor stands or wilting. If you see anything suspicious out there let us know and we’d be happy to take some plants off your hands. Thanks!





Surveys and Forecasts

So far there have been no reports of insect levels of concern to crops in Manitoba, or of populations of crop feeding insects potentially blowing in. We have had some winds from the south, but there have been no reports of populations of aster leafhoppers moving towards Manitoba, as happened early last year.
The counts in the diamondback moth traps have been very low so far. The highest counts so far are 8 from a trap near Steinbach, and 2 from a trap near Carman.


Cutworms: Cutworms are needed for a project studying parasitism in our local populations of cutworms. This project aims to gain a better understanding of cutworm parasitoids, and whether there are ways we can create conditions to enhance levels of these parasitoids. So please let us know if you are finding cutworms in any fields. Save some for the study, or we will come to the field to collect them. Please contact Dr. Barb Sharonowski at the University of Manitoba (204-474-7485) or myself (204-745-5668). 

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