The codling moth is both the proverbial and literal ‘worm in the apple’ when it comes to pome fruit. It remains the number one pest of pome fruit around the world, even after a century of pesticide arms races and the development of environmentally-friendly innovations like pheromone-based mating disruption and mass trapping.
The changing climate is working in the codling moth’s favour, and the apple industry in Washington State has recently struck a codling moth task force to grapple with continued seriousness of the pest.
At the annual Orchard Pest and Disease Management Conference in Portland this January, a retiring researcher shared codling mothcontrol data from the early 1900s.
Even after treatment with lead arsenate, the codling moth survival rate was still a remarkable 10 percent. Then along came DDT and then Guthion, both of which have long been replaced with softer formulations.
Pheromone-based mating disruption was a key innovation that allowed growers to reduce the number of spray applications required.
Codling moths that can render an apple crop worthless in other regions have been significantly controlled in the Okanagan through the Sterile Insect Release program.
Most apple growers around the world use some combination of pheromones and pesticides, except in B.C. where an innovative sterile insect release program has been operating since the 1990s.
In the Okanagan and Similkameen valleys where the Okanagan-Kootenay Sterile Insect Release Program (OKSIR) operates, nearly half of the apple acreage is considered codling-moth-free.
Most growers in the program’s service area do not need to use any supplemental control sprays for codling moth, and some growers haven’t needed to spray in well over a decade. Data from the program shows that the amount of pesticide used against codling moth in the region has decreased by over 90 percent since the program was put in place.
The OKSIR Program rears millions of the moths in their custom-built facility in Osoyoos, B.C., just minutes north of the U.S. border. Moth larvae, the ‘worm’ stage of the codling moth life cycle, are raised in cafeteria trays filled with a bran muffin-like diet with a texture and moisture profile similar to the inside of an apple. The larvae spend several weeks in the tray eating and growing bigger. When they are ready to pupate, the humidity in the rearing rooms is dropped so that the diet in the tray dries out—it becomes less like an apple and more like the bark of a tree where codling moths like to pupate in the orchard.
The moths pupate at the surface and when the adults are ready to emerge, they leave their pupal casings and fly into the room. These specialized emergence rooms are kept pitch black, except for four slivers of light in the ceiling. As moths are wont to do, they fly toward the lights where they are immediately sucked up by a vacuum in the ceiling. They are sucked along tubing and into a specialized collection room where the temperature is kept around two degrees Celsius, cool enough to immobilize the moths.
Here the chilled moths are put into paper deli cups, about 3,200 moths per cup, half males and half females. A small portion of the moths are held back to mate and continue the facility’s production and the rest of the moths are exposed to a small amount of radiation. The radiation leaves the moths sterile but still sexy, which is the ultimate goal of any sterile insect release program—strict QA/QC protocols are in place to ensure that only properly sterilized moths leave the facility.
The sterile moths are released at least once a week into the orchards where they find and mate with wild moths—offspring from these matings are not viable.
The program was built on the research of scientists at the Summerland Research and Development Centre, part of Agriculture and Agri-Food Canada’s network. OKSIR is now entirely operated locally and it is funded with a combination of an acreage tax for pome fruit growers and local property taxes.
This built-in-B.C. program is the envy of apple-growing regions around the world and many countries are now trying to figure out how to start their own programs. New Zealand, Australia, France, the U.S. and South Africa are among the countries that have imported sterile moths from the OKSIR program for pilot programs and feasibility studies.
When I was invited to contribute to this Innovation Issue, I knew I wanted to share a glimpse into the OKSIR Program. Not just because I am proud to have spent the last nine years at the helm of OKSIR, but because the program is a testament to the power and possibilities when people think big.
There are a lot of challenges in our industry that seem nearly insurmountable—they require innovation and big thinking. But if the B.C. apple industry could do it with OKSIR in the ‘90s, we can certainly do it again.
Melissa Tesche is the general manager of the BC Fruit Growers’ Association.