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Manitoba Agriculture, Food and Rural Initiatives

Manitoba Insect and Disease Update

June 14, 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

• Rust has been found on wheat in southern Manitoba
• Plants in some retail chain stored in Manitoba have been found to contain late blight
• Cutworms continue to be a problem in some areas of Manitoba.
• Diamondback moth counts continue to increase in traps, with highest counts in eastern Manitoba.

Recent Insect and Plant Pathogen Activity

Rusts on Cereals: An agronomist from Cargill found rust on wheat in the Winkler region over the past week. The spots were identified as Leaf Rust (Puccinia triticina synonym P. recondita f.sp. tritici) and Stripe Rust (Puccinia striiformis f.sp. tritici). It is an early incidence and the severity of the disease will depend on the weather over the remainder of the summer.

Leaf spot diseases: On spring wheat, Tan spot is currently the most common leaf spot; few spots of septoria leaf spots are also being reported.

Sclerotinia: Apothecia of Sclerotinia were also found this past week. They were found in a wheat field, which was in beans in 2009. With current conditions of high humidity and some volunteer canola seen all over, there is a possibility of volunteers showing earlier disease symptoms.

Late Blight on plants in retail stores: Some tomato plants on the shelves in a retail chain store in Brandon were recently found to have late blight symptoms. Plants at some retail chain stores in Winnipeg were also examined and there too late blight infected plants were found. All infected plants were confirmed to be late blight infected by microscopic examination of the pathogen spores. Report of late blight this early in the season is worrisome to the potato industry, which needs to be cautious of this disease.

Cutworms: Cutworms continue to be a problem, with several recent reports of problems from western Manitoba. Dingy cutworm is one of the dominant species this year. They overwinter as larvae, and should be finished their feeding soon.

 

Surveys and Forecasts

Diamondback moth: Some traps in Manitoba continue to catch high levels of diamondback moth adults, with the highest counts still in eastern Manitoba. Highest counts so far are:

Location of trap

Recent Count

Total count since early-May

Landmark

127

353

Beausejour

111

256

Dugald

28

216

Sewell

67

196

Kleefeld

54

191


The highest single week count is still the 137 near Dugald 2 weeks ago.
The highest count from Central Manitoba is 135 from a trap near Oakville.
The highest count from western Manitoba is 82 from as trap near Griswold.

Diamondback moth do not overwinter well on the Canadian prairies but can get moved here on winds.
The trap counts have alert us to the fact that
• the moths have moved in early this year, and in significant numbers
• the eastern part of Manitoba seems to have been where highest levels were deposited.

Knowing this, it is now important that monitoring for diamondback moth larvae be an important part of canola crop scouting this summer.

In some years parasites or inclement weather can help keep levels of larvae low, even when large numbers come in early. But whether this is the case in 2010 will not be known for awhile.

The other risk is that with the early arrival they may go through an extra generation than if arrival had been later. This extra generation can help build the population if they are not well regulated by natural enemies or weather.

Traps for monitoring diamondback moth can be removed after counts for this week, since we now have the information that we need from these traps. Once we get into the second generation it would not be clear whether trap counts are new arrivals that got blown in, or second generation adults.

The important thing now is to focus on looking for the larvae. If any fields are found to contain high levels of diamondback moth larvae, please alert myself or a nearby Farm Production Advisor so we can provide alert in future Manitoba Insect and Disease Updates of any regions where high larval counts are starting to appear. The photo below shows a picture of a diamondback moth larva and pupa:

Diamondback Moth

Data for the diamondback moth monitoring program is updated at the beginning of every week on the MAFRI website at: Diamondback Moth Forecasting Program

Bertha Armyworm Monitoring: Trap counts are just stating to come in, and it appears that adult emergence is just starting; only 0, 1 or 2 in the traps reporting so far.

A reminder to anyone involved in monitoring adults of bertha armyworms that traps can now be set up. A protocols for setting up the traps can be found at: Trap Assembly and Monitoring Protocol for Bertha Armyworm

Data for the bertha armyworm monitoring program is updated at the beginning of every week on the MAFRI website at: Bertha Armyworm Monitoring Program