At what times of the day are swede midge males most frequently searching for mates?
To answer that question, one must observe the patterns in their activity for 24 hours. Elisabeth and the U. of Guelph technicians set up pheromone traps baited with swede midge pheromone lures in collard, kale, broccoli, and cauliflower fields around an organic farm in New Hamburg, ON and checked the traps each hour for 24 hours. We caught the most midges in the traps in the early morning and evening, which suggests that males are more active at these times of the day.
Our campsite at the farm, complete with microscopes for identifying midges on the sticky cards from the traps. Coffee on the camp stove was a must for this experiment!
Perks of staying up all night: You get to enjoy beautiful sunsets and sunrises out in the field.
Why do we care when the midges are active?
We are developing a pheromone mating disruption system to manage swede midge organically. A large quantity of pheromone is required to formulate dispensers that will sufficiently confuse the males so that they cannot find their mates. One major challenge with this system is that the swede midge pheromone blend is extremely expensive to synthesize. One way to reduce costs for this practice is to only release pheromones from programmable dispensers (such as these) in the field when the insects are active. High-tech dispensers in the future could be programmed to turn off in the afternoon and at night, when the midges are resting or not searching for mates, reducing the cost of pheromone inputs for a mating disruption system.
In addition to the practical applications of this type of study, behavioral observations are important for understanding an insect species’ ecology. Timing of pheromone release and flights vary between species to achieve reproductive isolation. Insects may be more active during the times of the day when environmental conditions are more favorable for their survival. Our research group aims to learn more about swede midge and its interactions with the environment and our agroecosystems in North America.
Glenna Malcolm at Penn State University and I have just published a case study for ecological thinking from my previous work on sunflower domestication and tritrophic interaction.
The study can be found at NSF’s National Center for Case Study Teaching in Science.
With the beginning of summer last week came the onset of our season of field trials. Graduate student Elisabeth Hodgdon is spending the summer at the University of Guelph in Guelph, Ontario working with our Canadian collaborator Rebecca Hallett testing a new organic management strategy for swede midge, pheromone mating disruption.
Female insects secrete sex pheromones to attract males for mating. Pheromone mating disruption involves the application of large quantities of a pest’s sex pheromone within a field using slow release dispensers. When this chemical signal is ubiquitous in the field, the males become confused and cannot locate their mates (insert witty comment about confused males here!). Crop damage is reduced when the insects cannot mate and females do not lay eggs on the plants.
Pheromone dispenser in the field. Each semipermeable bag contains a small vial that slowly releases the midge pheromone throughout the season at a quantity 100x the amount produced by a single female in her lifetime.
University of Guelph Elora Research Station in southwestern Ontario
The main challenge associated with mating disruption of swede midge is that the pheromone is extremely expensive to synthesize for field application. This summer Elisabeth is testing whether a cheaper, racemic blend of the pheromone compounds will effectively confuse males and reduce damage in a broccoli test crop compared with the more expensive, chiral blend of pheromones naturally produced by the females and an untreated control. The treatments were set up on a commercial farm in New Hamburg, ON and at the Guelph Elora Research Station last week. She will collect trap data within the plots and harvest the broccoli at the end of the season to measure the treatments’ ability to improve marketable broccoli yields.
Swede midge is causing dire economic losses on organic vegetable farms in Ontario, Québec, New York and Vermont, and is spreading to nearby states and provinces each year. The midge was first documented in North America in southwestern Ontario in 2000 and populations have since become well established there, making the area ideal for researching new management strategies. We hope to further our collaborations with Canadian researchers in the future so that we may find solutions for growers in both countries.
Vic is joining Plant and Soil Science at UVM as a Full-time Lecturer! The department is very lucky to have some who is has such a passion for teaching and student mentoring.
I am very pleased that we have been able to retain Vic at UVM!
Swede midge is an insect pest that has recently caused up to 100% losses of organic broccoli in New York and Vermont. The midge is an invasive pest that also attacks a wide range of other crops in the Brassicaceae family (kale, collards, cabbage, kohlrabi, Brussel sprouts, bok choi, napa cabbage, turnips, and canola). So far, severe damage is only restricted to New York and Vermont.
The Insect Agroecology and Evolution Lab is the currently the only lab in the United States that is working on the developing alternative pest control strategies suitable for organic production for the midge. If you donate to our fund, the money will go directly towards funding student research on swede midge pest control.
Help support swede midge research!