Evaluation of Alternative Planting Strategies to Reduce Wheat Stem Sawfly (Hymenoptera: Cephidae) Damage to Spring Wheat in the Northern Great Plains

Abstract

Wheat, Triticum aestivum L., producers are often reluctant to use solid-stemmed wheat cultivars resistant to wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), due to concerns regarding yield, efficacy or market opportunities. We evaluated the impact of several planting strategies on wheat yield and quality and wheat stem sawfly infestation at two locations over a three-year period. Experimental units consisted of large plots (50 by 200 m) located on commercial farms adjacent to wheat stem sawfly-infested fields. Compared with a monoculture of a hollow-stemmed cultivar ('AC Barrie'), planting a monoculture of a solid-stemmed cultivar ('AC Eatonia') increased yield by an average of 16% (0.4 mg ha(-1)) and increased the grade of wheat by one unit at the two most heavily infested site-years. Planting a 1:1 blend of AC Eatonia and AC Barrie increased yield by an average of 11%, whereas planting 20- or 40-m plot margins to AC Eatonia increased yield by an average of 8%. High wheat stem sawfly pressure limited the effectiveness of using resistant cultivars in field margins because plants were often infested beyond the plot margin, with uniform infestation down the length of the plots at the two most heavily infested site-years. The effectiveness of AC Eatonia to reduce wheat stem sawfly survivorship was modest in this study, probably due to weather-related factors influencing pith expression and to the high abundance of wheat stem sawfly. Greater benefits from planting field margins to resistant cultivars or planting a blend of resistant and susceptible cultivars might be achievable under lower wheat stem sawfly pressure.

Host selection by the wheat stem sawfly in winter wheat and the role of semiochemicals mediating oviposition preference

“…Wheat stem sawfly oviposition behavior, as in other insects (Hattori, 1988;Nottingham, 1988), is a process involving different host location cues as well as host acceptance cues (Ramaswamy, 1988). Improvement of trap crop effectiveness is needed before this practice is widely adopted (Beres et al, 2009) and the results obtained in the present study indicate that the choice of trap cultivar can have an impact on WSS preference, leading to a concentration of feeding larvae in the trap. Improvement of trap crop effectiveness is needed before this practice is widely adopted (Beres et al, 2009) and the results obtained in the present study indicate that the choice of trap cultivar can have an impact on WSS preference, leading to a concentration of feeding larvae in the trap.…”

Solid-Stemmed Wheat Does Not Affect Overwintering Mortality of the Wheat Stem Sawfly,Cephus cinctus

“…Together, these biological factors inflicted higher mortality than winter conditions, and their contribution increased significantly in each successive year of the study. In 2006, ∼ 5% of stubs cut by sawflies (39 cases) had a large circular hole on the plug, suggesting predation by a beetle (Morrill et al 2001; Beres et al 2009); only one and 13 sawfly larvae were killed by this predator in 2004 and 2005, respectively.…”

An Artificial Neural Network Model to Predict Wheat Stem Sawfly Cutting in Solid-Stemmed Wheat Cultivars

“…The conclusion reached was that pith expression is suppressed in conditions of sustained days with precipitation because the amount of light a plant receives is suppressed. However, the fit of predicted vs. actual cutting was modest (R 2 = 0.55) using the model, and other attempts to use the regression model to explain variability in solid-stemmed wheat susceptibility have produced inconsistent results (Beres et al 2009). …”

“…Producers in the past have been reluctant to adopt solid-stemmed wheat as there was a perceived yield penalty when growing solid-stemmed wheat and a concern that increased wear on harvesting equipment occurs when threshing solid stems (B. Buckman, personal communication). Beres et al (2009Beres et al ( , 2007 and Nilsen et al (2016) demonstrated that solid-stemmed common and durum wheat can be agronomically superior to hollow-stemmed wheat, particularly in the presence of sawfly pressure. Lillian , the latest solid-stemmed cultivar, has occupied up to one-third of the wheat hectares in Saskatchewan and 20% of the prairie-wide wheat hectares (Anonymous 2010).…”