Manitoba Insect & Disease Update

Issue 1:  May 24, 2017

 
Summary
 
Insects: Insect pest concerns are currently low overall. There have been some insecticide applications for cutworms in the Northwest, and for flea beetles in canola in the Central and Northwest Regions.
 
Plant Pathogens: Striped rust has been reported from a winter wheat field; no other plant pathogen activity has been reported.
 
Stripe Rust Overwinters in Winter Wheat

Stripe rust was observed in a winter wheat field near Austin this spring. This field was being monitored by local agronomist, Amber Knaggs, as there were disease issues, including stripe rust, already present last fall. When stripe rust is well-established in the fall and heavy snowfall provides a good insulating layer, the pathogen can overwinter even in harsher climates. Alberta also reported overwintered stripe rust this year, as has been observed in that province in the past.
The disease was detected over a month ago and the field has been continuously monitored this spring. The disease has not progressed much at this point (picture is from May 12th). Stripe rust typically likes cooler weather with adequate moisture available. Growers in the area surrounding this field should scout both their winter and spring wheat to determine whether the infection has spread. If fields are planted to a variety susceptible to stripe rust, infection is present, and the weather remains conducive to the spread of disease an early fungicide application (at the herbicide timing) may be warranted. For growers in the rest of the province, the main source of inoculum for stripe rust (like stem or leaf rust) remains when large spore loads begin to blow up from the southern United States.
It is interesting to note that in the field where stripe rust was observed, the grower had seeded two varieties, CDC Falcon (rated “S” for stripe rust) and Emerson (rated “MR” for stripe rust). The disease was only detected in the areas seeded to CDC Falcon.
                                                
                                                         Photo courtesy of Amber Knaggs.
 
Review of Soil Insects  
 
Several primarily soil-dwelling insects have been noted by crop scouts. It is good to know the potentially harmful from those that won't feed on crops. Below are 4 images of insects found in the soil, 2 are potential crop feeder and 2 do not feed on crops. See if you can determine what all 4 of these are.
a)                                                                                                     b)
             
c)                                                                                                                  d)
 
A) - This is the larva of a crane fly. They will have no legs at all. They are not crop pests. 
B) - This is the larva of a stiletto fly, sometimes also called therevid flies. These are predators and will not harm crops. They also do not have legs, but will thrash around a lot when disturbed. Don't confuse these with wireworms.
c) - This is a dingy cutworm larva. They will feed on many crops and weeds. There are reports that they are starting to pupate already in some fields in Manitoba. They will have three pairs of true legs at the front, 4 pairs of short and stubby legs in the middle of the body called abdominal prolegs, and a pair of prolegs at the back called anal prolegs.
D) - These are wireworms. They also will feed on a variety of plants. They have 3 pair of small legs at the front, but no prolegs.
  
Insect Monitoring Programs
 
Diamondback Moth: Diamondback moth monitoring with the pheromone baited traps has been underway since the beginning of May. Some moths have been caught in the traps, but levels so far have been low. Out of 70 traps, 41 had cumulative counts of 0 as of May 20. Table 1 below summarizes the highest cumulative counts in Manitoba.
 
Table 1. Highest cumulative trap counts for diamondback moth adults over the trapping period May 1 to May 20, 2017.
 
Location Count
Ste. Elisabeth 12
Fisher Branch 5
St. Adolphe 5
Lockport 4
Morris 4
Ste. Agathe 4
 
A more detailed update of diamondback moth counts in Manitoba is available in the Manitoba Agriculture website at: https://www.gov.mb.ca/agriculture/crops/insects/diamondback-moth-forecast.html
 
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Compiled by: 
 
John Gavloski, Entomologist                    Holly Derksen, Field Crop Pathologist        
Manitoba Agriculture                                   Manitoba Agriculture
Phone: (204) 750-0594                              Phone: (204) 750-4248      
 
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 contacts.
 
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.