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Manitoba Agriculture, Food and Rural Initiatives

Manitoba Insect and Disease Update

May 25, 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.


Summary

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

Recent Insect and Plant Pathogen Activity

Cutworms: Cutworm damage in oats, canola and sunflowers has been reported from fields in the MacGregor – Bagot area. Some spraying for cutworms is occurring in this region, and a field of canola was quite badly damaged. Redbacked and dingy cutworm are thought to be the more prevalent species doing the damage.

Another species of cutworm that we don’t see as much, known as black army cutworm, was found feeding on alfalfa in the Interlake. Like dingy cutworm, this is a species that overwinters as a partially grown larva, and can be quite large early in the season.

Below are pictures of black army cutworm, dingy cutworm, and redbacked cutworm.

Black Army Cutworms Dingy Cutworms Redbacked Cutworms

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. In some instances part of the problem is wheat curl mites surviving in fields that were canola last year but had volunteer winter wheat, from wheat that would have been planted 2 or more years ago, acting as a host for the mites. In some of these fields glyphosate had been used to kill the volunteer wheat, but the farmers had not waited long enough after applying the glyphosate before seeding this year’s wheat. Depending on conditions, it may take a few days after glyphosate application for the plants to die, and to kill the mites it is important to have a period of at least 7 to 10 days of no live grassy crops or grassy weeds to prevent live grassy plants “bridging” the mites to the next crop.

 

Surveys and Forecasts

Diamondback moth: Adult diamondback moths have been found in pheromone-baited traps in several areas of Manitoba. Highest counts are from the Eastern part of Manitoba. Some of the higher counts are 68 from a trap near Landmark, 66 from a trap near Altona, 59 from a trap near Carey, 33 from a trap near Killarney, and 27 from a trap near Dufrost. Diamondback moths arrived early this year. Conditions have been good for survival and egg-laying, and with favorable weather in the forecast diamondback moth could get off to an early start. Traps for diamondback moth are placed in fields (even if not yet seeded) in early May to monitor when diamondback moths begin to arrive in Manitoba.

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

Cereal Leaf Beetle: Last year cereal leaf beetle, which is a new insect in Manitoba that will feed on cereal crops, was found in the Swan River area. We are still not sure of the full distribution of this insect in Manitoba, and trying to get a better idea of where it may be present. Attached below is a link to a monitoring protocol for cereal leaf beetle that has been used for several years in western Canada to determine the extent of cereal leaf beetle.

Several fields in the Swan River area will be monitored for this insect, but it may be good if fields in other areas of Manitoba are monitored as well. So if interested in sampling a few fields in your area, the help would be appreciated. Have a look at the images in the protocol; reporting any suspected occurrence of cereal leaf beetle would be appreciated.

If the technique suggested in the protocol takes too long to fit between farm visits or fit into your normal monitoring program, then please modify it to suite your needs. It may be good to examine the contents in the nets after 25 sweeps; sometimes there is too much debris in the net after the 100 sweeps the protocol currently recommends.

Any winter cereals can be sampled stating immediately (mid-May) until the end of June. The general recommendation in the protocol is to sample spring cereals from mid-June to early July. With the warm spring so far, this can be modified for this year to sample from the beginning of June until early-July.

The protocol that is generally used is found at the following link:
http://www.westernforum.org/Documents/PPMN%20Protocols/2010_CLB%20protocol.pdf

Please forward this to others in your region who may be out scouting in cereal fields; the more people looking the better. And please send me any suspected positive identifications so we can get these verified.