2010 Wheat Stem Sawfly Forecast

The area at risk of economically significant sawfly populations in 2010 will be lower than last year. The 2009 field margin survey shows low populations in most of the area surveyed including the traditional sawfly areas in the Special Areas and the M.D of Acadia. Some areas of southern Alberta still have populations that are high enough to result in significant damage to wheat crops if conditions are favorable. The highest populations of sawfly were found in Forty Mile and Cypress counties south of Bow Island and north of Foremost and south of Medicine Hat.

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The Wheat Stem Sawfly Map is based on cut stem counts conducted after the 2009 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 very high proportion of wheat stems cut in the fall of 2009 will produce adults. Producers in areas with moderate to high levels of cutting should consider using solid stem wheat as a control strategy.

Female sawflies lay eggs inside grass and grassy crop stems; the eggs hatch and tunnel inside stems until near harvest. At harvest the sawfly larva migrates to the stem base and cut it. 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. For more information about the lifecycle can be found at Wheat Stem Sawfly Life Cycle.

Our experience over the past few years shows us that it is possible that higher 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 25 percent in the 2009 crop 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.

Parasitism can reduce populations and reduce the level of cutting. A small 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 resulting in lower sawfly populations under Alberta conditions.

For more information of sawfly and their management contact the Ag-Info Centre at 310-FARM (3276).

Wheat Stem Sawfly FAQ

Economic thresholds for wheat stem sawfly