Our program deals only with codling moth, which is the most serious pest of apples and pears. If left unchecked, codling moth populations can explode and damage almost every piece of fruit on a tree. The SIR Program was started in the 1990s to reduce the environmental impacts of the chemical sprays that commercial growers were using to control codling moth. To this end, the program has been very successful. The last estimate, calculated in 2018, shows that since the beginning of the SIR Program, pesticide use against codling moth has dropped by well over 90%, keeping our shared air and watersheds cleaner. Many of the Okanagan’s commercial orchards (66% of acreage in 2020) do not have to spray at all to control codling moth—a feat that has made our program the envy of apple-growing regions around the world. One of the main reasons for the program’s success is the area-wide approach. Unfortunately, pests don’t respect property lines, so a big part of the program is monitoring and controlling as many wild moth population sources as possible.

What services does the OKSIR Program Provide Orchardists?

Our program releases sterilized moths into every apple and pear orchard in the program’s service area (Salmon Arm to Osoyoos to the Similkameen). We bait and check weekly a network of over 3400+ codling moth traps in orchards, band orchard trees for monitoring, check fruit for damage during the season and at harvest time, and advise orchardists on additional control measures required in their orchards. The goal of the program is to keep damage from codling moth to less than 0.2% at harvest time. That means only one damaged fruit for every 500 harvested from the orchard. It is very tough to make a living farming apples, and excess codling moth damage can be economically devastating for growers.

What Does this Program Mean for Backyard Tree Owners?

Because backyard trees can be a wild moth population source and moths don’t care about fence lines, it is important that backyard trees are kept codling moth free, which is not an easy task. When the program began, the hope was to eradicate all codling moth from the valley. During this time, backyard tree ownership was discouraged, and the SIR program tried to monitor every backyard tree in every city in the service area—an expensive proposition! When the program goal shifted to suppressing the population rather than trying to wipe it out entirely, the program switched to monitoring only trees within a short distance (200-250m) of commercial orchards. Each year, as new orchards are planted and old orchards are removed, backyards will move in and out of the urban monitoring zone.

All backyard tree owners, not just those living within our current urban monitoring zone, have a responsibility to keep their trees free of codling moth. This doesn’t mean that all tree owners are automatically required to spray their fruit trees—trees with little to no codling moth can be managed with other means. Responsible fruit tree ownership is the goal, and this is not an easy task! Proper maintenance of fruit trees requires pruning, thinning of fruit, quick removal and proper disposal of infested fruit, and sometimes the services of licensed pesticide applicators. It is worth noting that requirement is the same for cherries and all other fruit trees and their many possible noxious pests—but monitoring and enforcement of everything other than codling moth would fall under the noxious best bylaw of RDOS (https://www.rdos.bc.ca/public-works/pest-control/tree-fruit-pest-control/).

Even pesticide sprays for codling moth are not a silver bullet for codling moth, and infested trees can require multiple sprays for multiple years before codling moth are really cleared up. Good pruning, fruit thinning, spray coverage, appropriate spray timing and cooperation from mother nature will all help improve the efficacy of sprays. Gone are the days of the really strong and effective insecticides that you could spray a tree with to kill moths on contact and get a month’s worth of coverage from a single spray—it turns out those pesticides were really bad for human health and our environment! Pretty much every insecticide registered for use against codling moth now is ‘reduced risk’—they are either designed to impact the eggs (laid on underside of leaves, so pruning and spray coverage is very important) or to be eaten be the tiny caterpillars as the enter the fruit (timing and good coverage very important). A perfectly timed and applied spray will only kill 90% of the targeted life stage. They are also designed to not last as long in the environment, so coverage periods for a single spray are relatively short and good control requires multiple applications at the correct intervals.

Why do I have to remove my fruit?

One of the ways to reset a tree with a codling moth population is to remove all the fruit from the tree for a number of years (usually 3, but possibly more). This is the most common action required of homeowners. It does not kill or harm the tree, which will allow the homeowner to keep the possibility of fruit production once the infestation is cleared. It takes more than one year of this process to get rid of a population, because codling moth larvae can remain dormant on a tree for multiple years, emerging when the conditions are just right.

Why do we have a codling moth problem that wasn’t here before?

Codling moths spread easily throughout the valley. Not just through backyard trees with infestation, but also from wild trees in ditches and hillsides, on abandoned properties, infested fruit bins, and woodpiles. One of the main culprits of moth movement is firewood. When apple orchards are removed, the temptation is to save the wood for firewood—who doesn’t love seeing ‘applewood-smoked’ on a menu, right? The problem is that codling moth larvae spend the winter under the bark of these trees, and they can stay dormant in the wood for between 1-3 seasons. So when wood is moved into a new area, the moths come out in the spring and go looking for a new food source. The program is locked in a constant battle of whack-a-moth!

How Can I Learn More?

Our website is a good source of information, and we are happy to hear from homeowners. You can call head office, in Kelowna, 250-469-6187, to speak to our staff Entomologist or myself, the General Manager. For West Bench specific discussions, contact Alexis Friesen, the Area Supervisor, 250-809-9920, or Colleen Blatz, Urban Supervisor for the area, 250-300-3893.

Kind regards,

Melissa Tesche General Manager, OKSIR

Melissa Tesche, B.Ed., M.Sc.

GENERAL MANAGER

Okanagan-Kootenay Sterile Insect Release Program

1450 K.L.O. Road, Kelowna, BC, V1W 3Z4

Tel: 250-469-6182, Cell: 250-488-5274

RDOS Pest Management Resources + Sterile Insect Release Program

The RDOS had a summer student put together the following videos and PDF resources for backyard fruit farmers.

OKSIR

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