The 2021 forecast in Saskatchewan and Alberta called for wheat midge in abundance. But what the annual prediction couldn’t take into account is what Mother Nature had in store.
“Wheat midge is really tied to rain. Areas that received enough spring rain to kickstart development had wheat midge emergence and a really good correlation with the forecasting data,” says Dr. Tyler Wist, research scientist of field crop entomology with Agriculture and Agri-Food Canada in Saskatoon, SK.
Drought conditions throughout much of the Prairies, however, left much of the predicted midge population dormant in the soil. “If the rains don’t come, the midge doesn’t come up out of the ground,” says Wist.
A surprising development in some areas was a second flush of the pest later in the season. “Second flushes can sometimes happen after another big rain event,” he says. “It’s like some of them just don’t start developing until after a second hit of moisture. It’s a mechanism that we need to further explore.”
There is also work to be done to better monitor wheat midge emergence and essentially ‘ground truth’ the annual forecast maps.
“There is no coordinated monitoring of actual wheat midge emergence to know if the maps and models are giving good predictions,” says Wist. “With SeCan, I conceived of a network of pheromone traps in their member fields that would have the growers and their agronomists reporting in real time during the 2021 season.”
Pheromone traps were distributed to volunteers (seed growers, independent agronomists and SeCan staff) across the Prairies and the initiative was dubbed ‘Midge Busters.’
The traps were placed in wheat fields and insect counts were done twice per week for one month. Participants entered their trap catches in an online platform so everyone could immediately see counts from other areas. Midge enthusiasts could follow along on Twitter under the #midgebuster hashtag.
“Ultimately, 67 fields were monitored with results showing midge in all traps with an average count of 50. Some traps had very low numbers, while others were as high as 1,350 midge per count,” reports Todd Hyra, SeCan Business Manager Western Canada. “The emergence rates will be correlated with rainfall data to help improve prediction models for the future.”
Hyra adds that the take-home message for many was the complexity of monitoring an insect that can come in multiple flushes. “It also reinforced the efficiency and convenience of growing Midge Tolerant Wheat as an effective and sustainable solution to a pest that has plagued growers for decades.”
What to expect for 2022
Should fields that expected high midge pressure in 2021 but missed a timely spring rain, be bracing for dormant midge to emerge in 2022?
Wist can’t say for certain. “We’ll know better when we see the forecast maps,” he says. Soon researchers will be heading into fields to collect soil samples that are the basis for these maps. “They pull the overwintering cocoons of the wheat midge out of the ground and open them up to see if they’ve been parasitized by Macroglenes penetrans,” explains Wist. The beneficial parasitoid helps to keep the midge population in check. “When a midge is parasitized it doesn’t go onto the map because it’s not viable.”
While growers await the maps, which are typically available in January, they can protect their wheat yields and quality by planning to seed Midge Tolerant Wheat and following stewardship protocols to keep the technology viable for future.
Wist says the Midge Busters initiative has given him a wealth of information that will help his team validate models and future predications. He is eager to build on the knowledge for next year. “Stay tuned for Midge Busters II in 2022,” he says.