Wheat stubble, particularly if it’s beneath 2021’s canola crop, has hidden value in the form of beneficial Macroglenes penetrans wasps that begin to emerge as the canola reaches early to mid-flowering stages.
In 2014, we were excited to observe high numbers of these mighty parasitoid wasps in our canola sweeps at several locations throughout the Peace River region and we were able to track the highest numbers back to canola standing above wheat stubble! Since then, we’ve tracked M. penetrans to even more sites throughout the region so we urge growers to consider that 2020’s wheat stubble contains a powerful ally – but only if they manage it well in 2021!
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| AAFC photo of Macroglenes penetrans. Photo: AAFC-Beaverlodge, S. Dufton” |
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| Graphic summary of the lifecycle of the wheat midge: Review Figure 6 (Image credit: Extension Entomology, NDSU) shared within the "Integrated pest management of the wheat midge" (Knodel 2016). https://www.ag.ndsu.edu/publications/crops/integrated-pest-management-of-the-wheat-midge-in-north-dakota |
Access more information related to this topic:
• Jorgensen, A., Otani, J, Evenden, M. 2020. Assessment of available tools for monitoring wheat midge, Sitodiplosis mosellana (Diptera: Cecidomyiidae). Environmental Entomology. 49(3): 627-637. https://doi.org/10.1093/ee/nvaa017
• Jorgensen, A., Evenden, M.L., Olfert, O., Otani, J. 2020. Seasonal emergence patterns of Sitodiplosis mosellana (Diptera: Cecidomyiidae) in the Peace River region, Alberta, Canada. The Canadian Entomologist. 153: 222–236. (Published Online 2020Jan15). https://doi.org/10.4039/tce.2020.76
• Dufton, S.V., Laird, R.A., Floate, K.D., Otani, J.K. 2020. Diversity, rate, and distribution of wheat midge parasitism in the Peace River region of Alberta, Canada. The Canadian Entomologist. (Accepted 2020Dec22; Published Online 2021Apr14). https://www.doi.org/10.4039/tce.2021.7
• Predators & Parasitoids Series 2 podcast entitled, “Secret Agents in the Stubble” where Jennifer Otani describes the relationship between wheat stubble and M. penetrans.
• A Growing Point article entitled, “Wheat midge parasitism in the Peace River region” which provides an overview about parasitism levels in wheat midge and its and dominant parasitid, M. penetrans.
• Learn more about midge tolerant wheat
• A fun infographic describing why and how wheat midge pheromone traps are used to assess risk (Jorgensen 2016).
• Field Heroes “Scouting for beneficials in cereals”
• Field Heroes new Field Guide (free PDF copy)
Finally, every year growers across the Canadian prairies have four valuable sources of information supporting their management of wheat midge:
1. Refer to annual forecast map to assess if fields in your region are anticipated to carry a higher risk of potential high densities of viable wheat midge in 2021 - Maps are normally available by mid-January and onwards for Saskatchewan and Alberta while the PPMN’s prairie-wide map is normally available in March. Before seed is purchased, growers can access these forecast maps to assess potential risk for wheat midge. Growers in high areas of risk should consider midge-tolerant cultivars. In June, review these maps to help gauge regional risk levels for wheat midge.
2. From June to July, access the Prairie Pest Monitoring Network’s “Weekly Updates” – Predictive model outputs are updated weekly through the growing season. These estimates use current weather data observed across the Canadian prairies along with biologically known parameters necessary for wheat midge to develop. More specifically, the outputs estimate dates when 50, 80, or 90% of regional wheat midge populations have begun to emerge from cocoons. Ideally, growers begin in-field scouting from 90% onwards in order to most accurately assess their actual in-field populations and apply economic thresholds (if they’re growing wheat cultivars susceptible to wheat midge).
3. By mid-June, track provincial weekly reporting resources to find updated estimates of regional wheat midge numbers intercepted in pheromone-baited traps (Alberta's Live Map, Saskatchewan’s Crop Production News, or Manitoba’s Crop Pest Updates). Cumulative counts of adults in the traps serve as estimates that again help growers prioritize the need for in-field scouting in their region. Every field can vary so in-field scouting is needed to accurately assess pest densities but also to refrain from spraying insecticide when numbers remain below the thresholds. In the latter situation, opting NOT to CONTROL preserves resident natural enemies like Macroglenes penetrans.
4. Links detailing how to perform in-field scouting AND the two economic thresholds for wheat midge are available from Alberta Agriculture and Forestry, Saskatchewan Agriculture, and Manitoba Agriculture and Rural Development.
