Manitoba Insect and Disease Update: June 4, 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

There have been two confirmed cases of Wheat Streak Mosaic Virus in winter wheat in the St.Claude/Elm Creek area. The earlier wheat plants show symptoms, the more severe the damage may be. The disease is often more prominent along field edges and becomes less evident towards the centre of the field. Be sure to scout entire fields to determine the extent of the damage. There is little information regarding the epidemiology of this disease, but the vector of the disease, the wheat curl mite, prefers temperatures above 20°C. Recent conditions have favoured vigorous winter wheat growth and have been unlikely to favour dramatic increases in wheat curl mite populations.
Some wireworm damage to cereals has been noticed in the Grandview area, and wireworm activity has also been reported in the Crystal City area. 
Seed treatments containing neonicotinoid insecticides can reduce the damage from wireworms, by putting them into a prolonged intoxicated state where they are not feeding, and get the crop off to a good start. But populations of wireworms may not be significantly reduced. Seeding into warm and moist soil, which can result in quick germination and early growth, can also reduce the level of damage by wireworms.
Some have also been asking about other white larvae that can be found in some fields. Larvae of stiletto flies (sometimes referred to as Therevids) can sometimes be found when looking for wireworms and cutworms. These are white and will have no legs, whereas wireworms will have 3 small pairs of legs near the front. Stilletto fly larvae are predators of things such as wireworms and earthworms. A behavioural trait you will note if handling Therevid larvae is that they will thrash around a lot when disturbed. 
     Figure 1. Wireworm                                    Figure 2. Larva of stiletto fly


Cutworm feeding has been reported from a few fields. Fields near Starbuck and Ste. Agathe have had insecticides applied to control cutworms, and in other instances agronomists are keeping watch over the level of feeding. Dingy cutworms seems to be one of the more numerous species this year. A factsheet showing some of the differnet types of cutworms in Manitoba can be found at:

We need your 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).  


Insect Monitoring Programs

Diamondback moth: Counts have generally been low so far from the diamondback moth traps. The highest trap counts have been from Eastern Manitoba. Highest counts are:

     Oldenburg - 40

     Steinbach - 14

     River Hills - 14

     Altona - 14

.    Emerson - 13

We do not seem to have received any high populations of diamondback moth arriving on any of the winds that have been from the south.

Bertha armyworm: For those who will be putting out traps for adults moths of bertha armyworm, I originally indicated that this week (June 3-9th) would be a good week to try to get the traps out. Based on degree day maps, development of the pupae is delayed this year, and emergence of adult moths should not happen too soon in Manitoba. So if you don't get the traps up this week, the week of June 10-16th would be fine for trap setup. 

Aster Leafhopper: Last year aster leafhoppers blew into Manitoba early and aster yellows was a big concern in some crops. So we are keeping track of levels and in Manitoba and in states to the south of us. The good news is that so far there is nothing to report. There have been no reports of aster leafhoppers in Manitoba yet, and in a recent conference call that included entomologists from states in the North Central U.S. nobody was mentioning aster leafhoppers being of noticeable concern. Historically, we have not had 2 bad aster yellows years back-to-back. So we are off to a good start this year to keep this trend.