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2018 Wheat Stem Sawfly Forecast

 
 
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The sawfly conducted in the fall of 2017 is a story of populations headed in different directions. The population of central Alberta (Camrose, Beaver and Flagstaff and Paintearth counties) has completely collapsed with no evidence of sawfly found in 2017. Meanwhile sawfly in the traditional area of southern Alberta has held steady and in some cases increased. More sawfly were found in Vulcan county and the M.D. of Acadia and the population remained steady in Lethbridge and Willow Creek. Overall sawfly populations remain low compared to the outbreak in the early 2000’s. The area most at risk of economically significant sawfly populations in 2018 will be in the Willow Creek /Lethbridge county border and southern Vulcan county

The damage ratings are based on 94 fields in 20 municipalities.

Four fields had moderate levels of cutting by sawfly (10-25 percent), two fields in the MD of Willow Creek and one each in Vulcan county and the M.D. of Acadia. Low levels of sawfly were also found across a wider area of southern Alberta. Despite the low level of sawfly in the survey and because of the random nature of the survey, individual fields may still have higher wheat stem sawfly populations than are indicated in the survey map. Please feel free to contact us if you feel the map does not reflect the situation in your area. Overall there were zero or very low (< 2% cut) sawfly numbers in 87 of 107 (81%) of fields surveyed. (Field locations denoted by a black dot had zero sawfly found in the survey.)


Eight years of sawfly survey at a glance

The Wheat Stem Sawfly Map is based on cut stem counts conducted after the 2017 harvest. The percent of stems cut by sawfly gives an indication of the number of reproductive adult sawflies that will emerge in late June through early July. Winter conditions have very little impact on sawfly populations and a high proportion of wheat stems cut in the fall will produce adults. Producers in areas with moderate to high levels of cutting should consider using solid stem wheat as a control strategy.


Wheat stem sawfly

Wheat stem sawfly damage

Wheat stem sawlfy larva in stem

Female sawflies lay eggs inside grass and grassy crop stems; the eggs hatch and tunnel inside stems until the crop starts to dry down near harvest. As the crop starts to ripen the sawfly larva migrates to the stem base and cuts a notch most of the way through the stem. Feeding damage from the tunneling can result in hidden yield losses of 10 to 15 percent. Further yield losses can occur from lodging at harvest. More information can be found at wheat stem sawfly life cycle.

It is possible that population hot spots still exist in areas of lower risk, individual producers need to be aware of the potential risks in their own fields.

Cutting levels higher than 10 to 15 percent or higher in the previous crop year indicate the need to consider seeding solid stem wheat to reduce sawfly losses. It is important farmers evaluate their individual situations in making their variety choices. When populations are low it is typical to have small localized populations of sawfly that affect only one field or even just a portion of one field. At lower populations wheat stem sawfly tends to have a very strong edge effect where they migrate into the current year crop from the previous year stubble.


Bracon cephi
Parasitism can reduce populations and reduce the level of cutting. A parasitic wasp, Bracon cephi, has been shown to have significant impact on sawfly populations.

The use of solid stem wheat varieties and the increase in parasitism are the major factors in lower sawfly populations in Alberta.
Frequently Asked Questions
Economic Thresholds

The 2017 wheat stem sawfly survey was carried out by Alberta Agriculture and Forestry with support from Farming Smarter and Chinook Applied Research Association. Thank you for your contribution.

Thank you Jan Lepp, Agriculture and Forestry, Brooks for managing the data from the field sheet to spread sheet.

Thank you David Giffen, Agriculture and Agri-Food Canada, Saskatoon for building the map.

For more information of sawfly and their management contact the Ag-Info Centre at 310-FARM (3276).
 
 
 
 
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For more information about the content of this document, contact Scott Meers.
This document is maintained by Shelley Barkley.
This information published to the web on November 29, 2017.