Codling Moth: The Canadian Experience | WSU Tree Fruit

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Good morning, or afternoon, if we happen to be running a little behind schedule. I am Melissa Teche, the GM of the Canadian SIR program, and it’s a pleasure to present now the Canadian experience with Coddling Moth IPM. We’ve been asked to share some of the successes and challenges of the program, but we only have 20 minutes to do that, so I won’t get into the storied history of our failed eradication attempt, but rather frame the presentation around the current IPM program that we run today.	Title slide. Presentation title: The Canadian (Okanagan) Experience: Codling Moth IPM: Successes and Challenges. Presenter information: Melissa Tesche, M.Sc., General Manager and Evan Esch, M.Sc., P.Ag., Entomologist.
I just said I won’t get into it, but it is worth noting that one relic from the failed eradication program is that it truly is an area wide program that we run in Canada, and all pome fruit orchards must participate in and pay for the OKSIR program. So that’s legislated by the provincial government. Some growers like it, some of them don’t, but we do provide a full service IPM program. And so since this is an IPM talk, I thought I’d organize it around the six principles of IPM. And they’re always a little different depending on where you look. So I thought I’d take the terms right from the WSU extension website. So the six components of IPM that I’ve got listed here and a little bit about how we fulfill each of those. And then we’ll go into each one in turn with what are the successes and challenges we have with that component.	Slide titled “Current IPM Program” contains a diagram of the codling moth lifecycle as well as a numbered list outlining six components of IPM: Prevention, Identification, Monitoring, Threshold Determination, Treatment, and Evaluation.
So the first component is prevention, and this is stopping an infestation from spreading. We have backyard wild tree orchard monitoring and compliance programs, and we do have legislated enforcement capabilities to get trees cleaned up or removed if we can’t get them cleaned up.	The speaker remains on the slide as she elaborates on the listed components of IPM
Identification is probably the second principle. This should be pretty easy. Most people know what a coddling moth looks like now, but it does require regular training of seasonal staff.
Monitoring is a very important component. We have a network of 3,400 traps over our 7,300 acres. We check them weekly. We make that data available in real time.
And the fourth one would be threshold determination. So when do you actually need to treat codling moth? And the more time I spend in this world the more I realize how rare it is that you don’t need to treat for codling moth but we do have that luxury in some areas of our program. But then when is the threshold for adding more moths or adding spray or adding mating disruption or some other supplemental tax on top of the base level of steriles that we provide, and when do the economics justify it for the farmer, but also for our program?
The fifth component would be selecting your treatment, and the principle is least toxic first, which we definitely do with use of sterile moths. It’s dropped pesticide use by a lot. But why sterile moths instead of mating disruption? And again, when more sterile moths? When should we select a spray versus adding MD?
And then, of course, the final and most important component probably is the evaluation. So is it worth it to run such a big program?
Getting right into that first principle of IPM, the principle of prevention. So in addition to the work that we do in orchards and preventing one infested orchard from contaminating their neighbors, we also work in the urban site. So the Canadian Okanagan is a real patchwork of urban and rural properties. You have backyards that are situated right against orchards. In the year 2000, we had over 5,000 urban sites that had backyard apple trees, and those were within 250 meters of commercial orchards. About a little less than half of those were infested in 2000. And you can see through program efforts that the number of sites has dropped now to fewer than 3,000 sites. But most importantly, the number of sites that are infested down to just a few hundred in the Okanagan. So really controlling those source populations. We do that with wild trees as well. We can remove wild trees and ditches, non-properties. And then, of course, within the orchards themselves, so preventing the orchards from becoming infested so that they spread that problem.	Slide titled “Prevention: Success” contains a bar graph of urban sites within 250 m of orchards for years from 2000 to 2021. Data is shown for both total sites visited and sites with infested apple trees. There is a consistent decrease in infested sites from 2000 to 2021.
So while we’ve had success with prevention, we also have a lot of challenges. It’s been lovingly termed a game of whack-a-moth here in the Canadian Okanagan. And hopefully it’s not too early to use this term, but probably our biggest challenge is super spreader events. Nobody wants to be the super spreader, but hotspots are really the Achilles heel of SIT. What we see is when acreage is removed, infested orchards come out, the wood gets piled and stacked left on the property, sold for firewood, and any overwintering larvae in that wood gets spread from neighborhood to neighborhood. We also see this problem with bin movement. Most Canadian growers still use wooden bins, which can be a real source of codling moth movement between infested and uninfested areas. And so we see this particularly around the packing houses where the bins are stacked up. So that’s an ongoing challenge, this game of whack-a-moth.	Slide titled “Prevention: Challenges” contains a bullet point list of “Super Spreader Events” noting issues with acreage removals and bin movement. A photo to the right shows excavators pulling up trees in an orchard block.
The second principle of IPM monitoring. This is something that the program does well. We have quite a huge network. We’ve got 3,400 traps that cover about 7,300 acres. That’s quite a high resolution trap network. We have riders that go out on ATVs. They check these traps weekly. They write the trap count on the trap, but then also input it in the computer that day so that the grower gets an email with their trap counts. It also gets put onto a GIS database, which is available for growers to see not only their property and their counts, but also their neighbor’s property and their neighbor’s count. So they have an idea if there might be a problem growing in a property next to them.	Slide titled “Monitoring: Success” contains two screenshots of the GIS database showing a map of codling moth counts for a specific area as well as a map with the total count for each property.
This is done at expense. And that expense is one of the challenges of our monitoring program. So it is expensive to run such an extensive trap network. Another challenge would be that there can be a time lag in the data. So if we check a particular trap on a Tuesday and a wild moth lands on a Wednesday, we might not find out about it until the next Tuesday when we come and check it. So that data can be as much as six days old sometimes.	Slide titled “Monitoring: Challenges” contains a screenshot of an interface showing trap counts for a site for a range of dates. There are gaps of six days or more between the date points and some dates are missing data altogether. Below this is a photo of a sterile codling moth, with a dyed red abdomen, and a wild codling moth with a grey abdomen. To the right is a bullet point list outlining the challenges of trap checking.
It’s very time consuming, not just to get to this network of traps, but to actually count the steriles and wilds in the traps. And so if you’re not familiar with our program, we do it by squishing the moths. Our insects, when they’re reared, are fed this red dye that makes them squish red as appears on the left hand moth of the screen. And you can see the abdomen of the fellow on the right, more like the color they appear when they squish on your windshield. And so our staff have to go out and squash all of these moths. and record the sterile and wild counts. And you can see from the middle column that they can catch as many as 349 steriles in a trap, and none of those show up to be wild. So that takes a long time. It also leaves them prone to human error. When you’re counting 304, 349, 235 steriles in a trap all day long, are you starting to miss those wilds, right? Do you become a little less attentive?	The speaker remains on the slide as she elaborates on the listed challenges of trap checking.
Or what if a trap checker is some degree of colorblind? Perhaps they miss it there. We’re certainly prone to human error on our trap checking. Then we also run into the problem of wasps and birds who will come and pick the traps absolutely clean. And then we get no data for a week, as you can see happened here on the week of June 27th and July 25th. We had no usable data from that trap. So those are a couple of the challenges with monitoring.
And then a bigger picture challenge with monitoring. Which lure is best? We still use the old school pheromone lure in our traps. We know that there are other lure options out there right now. Some of them are more attractive. Below, I have some work done by our program entomologist, Evan Esch, comparing the mean wild captures by each of the different lure types across our different release rates of sterile moths. So we can see that some of the more modern lures will catch more wilds. We’re not convinced that catching the most moths means that’s the type of lure that should be used. Instead, we’re more concerned with what information that lure is telling us.	Slide titled “Monitoring: Challenges” contains a bar graph of mean wild captures per trap per season for four different codling moth lures: CM, Combo, Combo AA, and DA AA. The data is presented for 3 different moth release rates: 800 per acre, 1600 per acre, and 3600 per acre.
Because really, the best lure for the program would be the one that best correlates with, or ideally predicts, codling moth damage. and that would allow development of an appropriate threshold for further intervention with supplementary tactics. In the same study as the captures presented on the left, Evan also did intensive damage sampling while comparing the lures to see which of those lures was most correlated with damage throughout the season. I don’t have time to get into this, and it’s too early to draw conclusions yet from one season of data, but the program isn’t averse to switching lures if one of the newer lures does a better job of predicting damage.	An additional graph appears on the right, which shows the percentage of damage seen for each lure type.
We’ll have to weigh, though, the benefits of switching against the cost of switching. You know, it’ll be very important to have a good understanding of what the new spray threshold would be with a newer lure. And that brings me to the next principle of IPM, the use of thresholds.
So our program uses a spray threshold based on the number of wild moths in a trap to guide growers on when to spray. Here’s a little bit of data from the last three years. And if we look at the data from 2021 based on wild captures, nearly 80% of the acres in the program did not reach a spray threshold. 5% of the program area should have applied one to two sprays and 9% of the area should have used three or more sprays. Now, whether or not the sprays got applied at the right time or at all is another story, but we do try to help our growers use a quantified threshold. We send them an email like the one pictured here for each of their traps to make it easy for them to identify when a threshold has been reached. And then we’ll try to follow up the email with a call from the area supervisor to make sure they’re on top of it.	Slide titled “Threshold: Success” contains a chart of the percentage of acres that did not reach spray thresholds in 2019, 2020, and 2021. The percentages for acres that did not reach the thresholds are above 70% for all three years. To the left, an example of the codling moth trap-count emails sent to the growers is shown.
But the use of a spray threshold has some challenges that we grapple with as well. The threshold we use has its origins from Vacanti and Madsen, 1976, which is a bit dated and wasn’t developed exclusively for SIT. A threshold should be built on economics, and the economics of spraying codling moths has certainly changed from the 1970s. But if you look at this pie chart of all of our program area last year, in the dark green, 52%, that area of the program had no detectable levels of wild codling moth, no wilds caught in their traps. And even the next green shade, 22%, had fewer than two wild moths caught in the orchard all season. The economics are easy there don’t spray. Similarly on the red and brown parts of the chart, high levels of infestation where the problem is getting worse, get some sprays on. But the middle portion, the 14%, the economics are less clear here. This is where we need to work to better understand what an appropriate threshold would be, depending on the type of apple, the type of planting, the type of product used, etc. There’s still work to do on that spray threshold itself.	Slide titled “Threshold: Challenges” contains the title and author information of the mentioned study as well as a pie chart of codling moth trends in the area for the year. Only 10% of the areas had an increasing level of codling moth, while the majority had no detectable wild codling moths.
And then never mind sprays for a second, but the age old question of SIT is how many moths do you need? The original work done by Dr. Proverbs reported a sterile to wild ratio in his study plots. And this 40 to one ratio became almost gospel in the codling moth SIT world. But since it’s virtually impossible to know what your total wild population is, the ratio of sterile to wilds in a particular trap can be examined instead. And in fact, the program would occasionally come under fire for not meeting sterile to wild ratios in traps. As we were trying to clean up a couple of really infested properties, we started dumping thousands and thousands of moths into a couple of these properties to see if we could clean them up by absolutely flooding them with steriles.	Slide titled “Threshold: Challenges” contains a plot of mean sterile moth recaptures per week for the three release rates: 800 per acre, 1600 per acre, and 3200 per acre. This data is shown for the four lures tested: CM, Combo, Combo + AA, and DA+AA. The moth recaptures initially increase for all lure types with higher moth release, but then level out from 1600 moths per acre to 3200 moths per acre. Text to the side of the graph outlines that sterile to wild moth ratio is virtually impossible to determine and is an outdated principle.
But a funny thing happened, and our sterile recapture numbers would hit a ceiling, no matter how many moths we treated the block with. So you can see that in this graph, that for all lure types, and this is done with four different types of lures, there’s a declining rate of sterile recaptures. So you really don’t recapture any more steriles with 3,200 moths per acre than you do with 1,600 moths per acre. And it’s tempting to say, well, your trap is saturated. It can’t possibly hold any more moths. But if you recall the trap data from an earlier slide that I shared for a trap in Kelowna, it’s certainly possible to catch 200 plus sterile moths in a single trap. And if you look at the graph here with the lure types, the DA+AA lure that averaged fewer captures than the other lure types, it shows the same declining rate of recapture	The speaker remains on the slide as she elaborates on graph.
Now Dr. Adams is going to want to say that this graph tells you that releasing at those higher rates is not worth it. We’re not quite ready to make that same strong conclusion because sterile recapture rate isn’t a direct measure of codling moth control, but it’s certainly something we’re looking at. So what is the threshold that you use to determine how many moths you put into a particular property? So that’s one of the challenges that we wrestle with thresholds.
Okay, on to the fifth of the principles, selecting the treatment. So the general principle is, you know, choose the most environmentally friendly option first, right? That desire to get away from OPs in the seventies, eighties, nineties was a driving force behind the program and the pesky failed eradication attempt. So SIT as the primary control tactic is what our program has by default. You can see from this graph though that it’s been fairly successful. So we’ve got the average codling moth per trap per week here from 1995 to 2021. It wasn’t rolled out through the whole service area all at once. It was rolled out from south to north in these zones. And so that’s why you’ve got three colored blocks for each year for the results. And the black arrows kind of show you where the sterile insect release started for zone two in the central and then zone three in the north. And so you can see that as a whole, the wild codling moth populations have really dropped since the program started. So altogether, area-wide codling moth is the primary control tactic. It’s been very effective, but also very expensive.	Slide titled “Treatment: Success” contains a bar graph of annual average codling moth captures per trap per week from 1995 to 2021. This data is shown for three different zones, which are indicated on a map to the right of the graph. Black arrows indicate when the program was started in each zone. There is an overall decline in codling moth captures from the start of the program to 2021.
So it would be natural to ask, you know, wouldn’t mating disruption be cheaper or better? And the program was certainly interested in this option, especially as the number of acres in the service area continued to decrease. So from 2011 till 2014, the central and northern regions actually switched over to mating disruption as a primary control tactic. So that’s the years with the stars over them. Now these capture data need to be interpreted with caution because the lures are switched to the more attractive mating disruption lure, but the damage sampling that we did at the same time, it held a similarly concerning trend and it showed that mating disruption was not holding down the wild population as well as sterile insect ECAD. And at the end of the 2014 season on the advice and external review panel, the program actually switched back to SIT as the primary control tactic.	Text appears above the graph: Would MD be Cheaper? Better?”. Stars appear over the results of 2011-2014 on the graph which show slightly heightened codling moth levels compared to the surrounding years.
This is probably another place where the spatial layout and the geography of the Okanagan cause problems. So our region really is this patchwork of small and, by Washington standards, tiny orchards. A 10 acre block is considered large here. And so we’re missing that huge contiguous acreage that seems to best position mating disruption for success. Still though, in some organic properties that struggle, we use mating disruption as a supplementary tactic, layering it over top of SIT. And that brings me to kind of the biggest ongoing challenge with our primary control tactic, which is moth quality.
The trick with sterile insects is that you need to make them sterile, but also make and keep them sexy. So wild females in the field won’t be wooed by beat up or scraggly moths, and we’re constantly refining rearing and collection techniques and transport and release protocols. Our collaboration with M3 has brought some great advances. The drone release is much gentler on the moth than being rattled around on an ATV and shot out the side of a moth cannon, which is our traditional way of distributing moths. And then the picture on the right is one of our proudest in-house innovations. You can imagine there’s not a lot of off-the-shelf options for codling moth rearing. But this is our collection device that’s improved our overnight collection quality dramatically. So there’s cool air is pushed through those baffles. The baffle holes that you see extend all the way to the back of the collection chamber and that reduces compaction as the insects are collected overnight. So collectively all of these improvements come into play when we think about the final principle of IPM which is evaluation of the program as a whole. And you might have guessed from the data we’ve already shared, our program is quite effective when we look at it in terms of wild captures, but does that translate to less crop loss?	Slide titled “Treatment: Challenges” contains photos of a codling moth collection device in the lab, an image of the drone used for releases, and an aerial photo taken by the drone of an orchard.
Absolutely. So the ambitious goal set for the program when they gave up on eradication was to have 90% of the acreage in the program service area with 0.2% or less fruit damage at harvest. We most often meet that goal, we did last year. So less than 0.2% is about one damaged fruit in 500. If we zoom in on the portion of our program that didn’t meet the damage target, you can see that most of these areas are only just off that mark.	Slide titled “Evaluation: Success” contains a bar graph of the fruit damage seen in 2021 versus the percentage of planted area. Less than 10% of the total area had more than 0.2% fruit damage.
Here’s a breakdown of that 10% not meeting target. And most of that acreage is actually below 2% fruit damage at harvest sampling. This is harvest sampling that’s done in the field by OKSIR staff. Yes, some damaged fruit is thinned off before harvest sampling. We certainly hope it’s thinned throughout the season. Of course, that’s considered part of the IPM process as well.	Slide titled “Evaluation: Success” contains a bar graph of the damaged fruit versus the number of orchards for the areas that had more than 0.2% fruit damage. The majority of the orchards shown had below 2% fruit damage.
Finally, a critical component of the evaluation of success for us as a program is the amount of pesticide that’s been saved by using a sterile insect technique. So this data is a bit old. It’s imperfect. It’s derived from sales numbers. It has been adjusted to a per hectare basis to account for declining acreage in the region. But you can see that since the beginning of the program in the early 90s, there’s been an over 95% reduction in the pesticides used against codling moth. And that’s a big win for reducing the speed on the pesticide treadmill and also for the residents of the Okanagan that help fund the program through taxes. So the social and political implications of the program are a whole other talk of successes and challenges. I’m happy to talk about that at length in another presentation at another time.	Slide titled “Evaluation: Success” contains a line graph of the kilograms of active ingredient applied per hectare from 1993 to 2016. There is a consistent downward trend to the application.
In conclusion, as a tactic, sterile insect technique is not a similar bullet, but it has been a solid primary tool in our IPM toolbox here in the Okanagan. And with that, I’ll conclude my talk. Thank you.	A conclusion slide titled “SIT: Main Tool in our Toolbox” contains an aerial view photo of the program area as well as a screenshot of the OKSIR website: www.oksir.org.
Music plays.	Credits for the presentation and video production roll.

Link to YouTube video: Codling Moth-The Canadian Experience