What's Growing ON?
What's Growing ON?
Back to Basics: Apple IPM Case Study
In this special extended episode, Cassie goes back to basics with co-host Kristy Grigg-McGuffin, Horticulture Integrated Pest Management (IPM) Specialist to talk about the components of what makes an IPM program using summer disease in apples as a case study. More information on IPM and apple-specific pest issues can be found on the Ontario CropIPM website.
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Have a question or a topic you'd like us to cover? Email us at ONhortcrops@gmail.com
Music: Aspire by Scott Holmes
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Kristy: This is What’s Growing ON? A show where we dig up the latest dirt on Ontario horticulture production, helping producers navigate best management practices and taste the sweet success of a quality crop. My name is Kristy Grigg-McGuffin.
Cassie: And I’m Cassie Russell. Join us as we talk to specialists in the field of fruit, vegetables and specialty crops to find out what’s really growing on.
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Cassie: Welcome to episode 7 of What’s growing ON. Hope everyone had a great August long weekend. This week, we have a special extended release for you on the basics of IPM with a focus on summer disease in apples. For this week’s episode, we apologize in advance for any background noises you might pick up. I’m sure a lot of listeners can understand and sympathize that home offices aren’t always distraction and noise free.
Next week, we will be back to resuming our normal episode format including crop updates and shorter fruit and vegetable segments. As always, for up to date Ontario specific crop updates, please check out our blogs – ONvegetables.com and ONfruit.ca
Without further ado, hope you enjoy this week’s special extended episode.
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SEGMENT 1: IPM Basics with summer apple disease
Cassie: So in the heat of the summer, we often see general pest pressure starting to ramp up around the province, Kristy and I were thinking it would be go back to pest management basics a little bit. And who better to cover that topic than our own co- host, OMAFRA’s integrated pest management specialist for horticulture, Kristy Grigg McGuffin.
Kristy: Thanks for having me on this side of the conversation!
Cassie: So yeah, as I said, lets go back to basics a bit here and talk about integrated pest management, or IPM. Can you describe what this is?
Kristy: The term “integrated pest management” is really nothing new. It has been around since the 1970s when ecological and social implications to pest management started to come to the forefront.
It’s a pest management approach that looks at the long-term prevention of a pest or their damage by managing the ecosystem in a way that is economically, environmentally and socially sustainable. So, in this decision making process, it brings together a combination of multiple control strategies to reduce pest populations below an economic injury level. We’re not talking about eradicating a pest but rather maintaining it at levels below which the damage would have a significant economic impact.
Cassie: So, if it’s not a new thing, why are we still continuing to focus on IPM?
Kristy: While it has been around for some time, IPM is a very dynamic concept and it is continuously evolving as agricultural practices change, our understanding of the agricultural landscape deepens and new technology is developed.
As well, the perception of what constitutes IPM has really changed. There is a lot that has been incorporated into standard programs now that growers wouldn’t think twice about. I think many, if not most, growers have some general understanding of their pest issues before spraying. Many think about impacts of environmental conditions on their pest complex or risk potential. These are components of IPM that have become so ingrained in regular practice that now when people think IPM they look at the advanced technology they haven’t yet adopted.
Cassie: If a grower is using IPM practices, what does that actually look like?
Kristy: It’s not one single program - which is why IPM is such a complex topic - but rather management is really on a continuum depending on the grower and their operation. Differences in geography and climatic variation, soil type, variances in pest complex, availability of labour, equipment and finances all influence the shape that an IPM program takes from one operation to the next.
The goal – at least from my role – is to just try and continue to move grower practices along the continuum as new technology is developed and adopted.
But I would say, overall, the foundation of any effective IPM program is consistent.and involves 6 key components to any effective IPM program:
1. Prevention
2. Identification
3. Monitoring
4. Threshold
5. Control
6. Evaluation
Cassie: OK. Maybe we could go into a little bit more detail of each of those?
Kristy: Definitely – I think what might be helpful is look at a specific pest issue as a sort of case study. What an IPM program looks like really depends on the pest so while it’s nice to speak in general terms, I do think it’s helpful to hear some concrete examples of a program in practice. Wondering what you’d think about talking summer diseases of apples?
Cassie: Sure! My apple knowledge is not quite as extensive as certain vegetables, but this will be a great learning experience for sure. So, why don’t you start with a quick background on some of the summer diseases that apple growers have to deal with?
Kristy: Summer diseases in apples typically refers to the fly speck and sooty blotch complex and fruit rots such as black rot and bitter rot. All of these fungal diseases really come into play mid to late season. I won’t go into specifics on what the damage looks like but if anyone is looking for more information they can go to our Ontario CropIPM page or check out my apple pest updates on the ONfruit blog. Generally speaking though, they cause direct damage to the developing fruit and can impact quality and yield.
Cassie: And those fungal pathogens will colonize on fruits as sizing throughout the summer?
Kristy: Exactly - We’ve been seeing an increase in pressure from these diseases in recent years. There are a number of factors that may be involved here – changing climate, reduction/change in registered control products, markets driving demand for more susceptible varieties, etc.
Cassie: OK, so lets start going through those 6 key components of IPM and managing apple disease – so, The first piece of the puzzle you said was prevention, right?
Kristy: Yes, so this is a really key step in management by actually preventing or at least reducing the potential for pest establishment in the first place. You don’t have to put the time and money in season into control of something that isn’t there. We’ll talk about controls in a little bit, but cultural and physical controls are often preventative measures.
Site selection has a big impact on the prevention of pest problems. Where possible, choose a spot that has good drainage and air flow. Prepare the land and reduce soil-borne pathogens with the use of cover crops. Be mindful of what your surrounding landscape is.
For summer diseases in apples, black rot can be found on dead or decaying plant tissue so it’s really common to have higher pressure in orchard blocks beside a woodlot. Clearing out some of the dead trees will reduce inoculum coming in. Similarly, fly speck and sooty blotch often overwinter on wild hosts like brambles, or wild raspberry and blackberry. Removing those from around the orchard can be a really effective management tool.
If you grow annual crops, then it’s crop rotation to break pest cycles or adjusting planting/harvesting dates. As well, choose resistant varieties where you can. In apples, there aren’t really varieties with known resistance to any of the summer diseases. However, there are varieties that are more prone to infection. For instance, any variety that really holds onto fruitlets during chemical thinning like Gala are quite susceptible to black rot as the pathogen can overwinter in these fruit mummies that form.
Prevention isn’t just prior to planting. Maintaining good plant health by fertilizing and irrigating where needed helps the plant defend against pests. For instance, with bitter rot on apples, this pathogen does really well in hot, humid conditions. There are some pathologists that believe reducing the heat stress on the fruit will reduce its susceptibility to infection. In other words, the fruit’s immune function gets knocked out when internal temperatures reach a certain level. Applying a sun protectant product such as Surround or Screen Duo and keeping up with a consistent irrigation schedule helps reduce that stress.
Cassie: Ok wow lot of preventative practices and tool, probably more than most would realize they have available. Ok, so next – identification ; now what is part of that component?
Kristy: Another really important part to an effective IPM program that will save you money and time. It’s important not only to be able to recognize a pest or its damage but to understand its biology and life cycle. You’re aware of when the pest is active; what conditions are conducive to growth or development – something like black rot or bitter rot need rain splash to spread spores and bitter rot can infect intact tissue whereas black rot needs a wound or natural opening to cause infection; what life stage or timing is easiest for control – with disease, control is preventative while an insect pest may have a life stage that is more vulnerable or which is the damaging life stage; what natural enemies are present and where it may overwinter. Having an understanding of this biology will help determine appropriate management.
For instance, fly speck and sooty blotch tends to not really come into people’s radar until rather late in the season when these markings start showing up on fruit. Without knowing the biology of these pathogens involved, it’s easy to make the assumption that control would be initiated at that point when symptoms develop. When in actual fact, fly speck and sooty blotch infection actually occurs 4-6 weeks after petal fall – sometimes even earlier. Then the incubation period before symptoms develop is about the same amount of time. So, while you may be just starting to see damage, the infection and timing for control actually happened weeks before.
Cassie: Honestly that is something so critical to remember and understand. You really need to know what pest you’re dealing with because like you said, sometimes when symptoms show up – you’ve already missed your window to control that pest. So I think that ties really well into the next part of IPM (which I would argue is probably the most important; and that’s maybe because I did my masters on improving monitoring pratices, but yes… what about monitoring!
Kristy: Once you understand the biology and life cycle of a pest, you can begin regular monitoring to determine the actual pest activity in your block or field. For example, if the pest or damage is actually present; what is the extent of damage or size of population; or if there are signs of the population increasing.
The black rot pathogen can infect multiple parts of an apple tree – leaves, fruit, limbs, trunk. Often times, you can find leaf symptoms well before the fruit has even started to develop giving a good indication there are active spores in the orchard which gives you a head start at protecting the fruit.
But, as I mentioned earlier, disease management is typically different from insect or signs of early infection as in black rot so the focus is on preventative control. Much of disease monitoring is looking at growth stage of the plant and whether conditions are conducive to infection plus the level of risk in the field based on historical presence of pest or regional pressure.
Bitter rot was originally an issue we considered a southern disease but have been seeing increased pressure because of the hot, humid summers we’ve been experiencing. In a year like this, it’s important to monitor weather as this hot spell we’re in is optimal for bitter rot development. Any rain event can cause infection and we could see many regions in quite a difficult situation if there are any gaps in management. But go back to last year, 2019 was a relatively wet and cool summer so it really wasn’t a bitter rot year which meant management didn’t need to be as intensive.
So, monitoring can be as simple as visual inspections on a biweekly or monthly basis to quite intensive weekly counts, trapping and weather monitoring. But it’s important to stay on top of monitoring. I see so many times that growers get busy with all the other tasks they have to handle, they let monitoring drop off the table. But it’s your early warning system. The earlier a problem is found, the easier it is to manage. So, if possible, it really is helpful to have someone on-farm or a hired scout or consultant designated to provide that regular monitoring information.
Cassie: Yeah that’s a really great point – see agruably the most important part IS monitoring! So, once your scouting report indicates a pest or damage is found, I know that a lot of times triggers a response at least in some growers minds that it’s time to control… but that’s not necessarily the case, right?
Kristy: Right, exactly. And that where the next component of IPM comes into play – action thresholds. This is where you make control decisions considering potential damage, cost of control methods, value of production and impact on other pests, beneficial organisms and the environment. Thresholds are going to vary depending on the pest – some have zero tolerance for damage on the market so it’s really a presence/absence whereas others are based number of individuals per leaf. It’s also largely how much damage the grower is willing to accept.
Thresholds are also going to vary depending on the control strategy. Many biological products are slower acting, either needing to establish themselves on the plant surface if the mode of action is competitive exclusion or the product may impact a stage in pest development. So, these need to be applied much earlier in pest activity.
Some pests have established thresholds, whether that’s number per leaf as I mentioned or a developmental model that uses weather data. For instance, a model for fly speck exists that determines the incubation period on wild hosts in the early season leading to the start of fruit infection as well as the incubation period on apples before symptoms develop. So, infection can occur starting about 180-190 leaf wetting hours after petal fall with symptoms starting to appear 360-380 leaf wetting hours after petal fall. Having thresholds like this help to time appropriate control strategies.
But there are quite a few pests that don’t have threshold information or models available, including fruit rots on apples. This is where record keeping is important to look at trends and really refine a program that works for you.
Cassie: OK – so lets get to the big pressing question here – what does control cover when were talking an IPM strategy?
Kristy: All the information leading up to this point is what is used to choose the best combination of control strategies. There’s 5 main categories of control: cultural, mechanical/physical, biological, behavioural and chemical.
Cultural control are practices that disrupt the pest or make the environment less suited to support it. I mentioned a few examples earlier with crop rotation and planting resistant varieties. Orchard sanitation is one of the key strategies for managing summer diseases in apples. This involves pruning and removing all dead or dying branches, removing fruit mummies and mulching decaying fruit on the orchard floor all of which act as sources of inoculum for black rot and bitter rot. As well, removing potential overwintering sites like wild brambles will help reduce fly speck and sooty blotch.
Mechanical and physical control make use of equipment, barriers or other means to kill a pest directly, block it out or make the environment unsuitable for it. This type of control is really common for weed control such as mulches, tilling, mowing as well as with bird and vertebrate management with bird bangers, deer fencing, etc. For summer disease management, while it’s not commonly used here in Ontario, netting can be used to cover the trees and prevent the introduction of fungal spores.
Biological and behavioural control are more commonly used with insect, weed and vertebrate pest management rather than disease. Biological control is the use of natural enemies like predators, parasites and pathogens. This is either through artificial release (eg., predatory mites) or enhancing the landscape to support natural populations. Behavioural control uses the pest’s natural behavior to suppress the population such as using mating disruption, pheromones, toxic baits and sterile insect release. Hopefully we can talk more about these controls in another podcast.
Cassie: Yeah, you’re right those alone are their own segement for sure. And something, like you said that’s a lot more common in insect control… but I feel like your building up to cover one more control strategy that can be especially applicable to controlling summer disease in apples…
Kristy: Lastly, another important type of control is chemical control or the use of pesticides –including synthetic, biological and organic. In IPM, pesticides are used only when needed and in combination with other approaches for more effective, long-term control as well as longevity of the control product (aka resistance management).
To understand chemical control for summer diseases in apples, we have to think about apple scab management. This is the primary disease for apples in Ontario. The way a typical program looks for scab is a fairly aggressive early season preventative program with fungicides going on regularly during times of rapid growth and periods conducive to infection which is warm and wet conditions. Once the primary apple scab period is over, which is typically mid to late June or maybe even early July, and no scab lesions are found, growers start to back off rates and extend intervals between sprays. Unfortunately, this means protection may be lacking for summer disease control.
Quite a number of scab fungicides have efficacy on summer disease. There is an efficacy table in our Publication 360A, Crop Protection Guide for Apples that lists these products. Keep in mind the preharvest interval and maximum applications for some of these products as you continue to use them into late season. It’s also important to pay attention to rate as with some products such as captan need the high rate for effective control of summer disease. So, after primary apple scab, it is still important to maintain regular fungicide coverage, keeping a 14-21 day schedule to ensure residue levels remain. If it is a wet season, this interval should be reduced to 7 days. And regardless of interval, reapply after 2 inches of rain since last application. Infection can continue right up until harvest so those late-maturing varieties may need management well into the fall.
There has been some really interesting research looking at residual control of fly speck and sooty blotch that suggest fungicides may not actually erradicate the pathogens but rather suppress development. These researchers limited fungicide applications at the onset of the infection period to allow for infections to occur. They then continued with a standard summer fungicide program and monitored symptom development into the fall following the end of the program. As residue levels declined, symptoms began to develop. This reinforces the importance of maintaining fungicide coverage as its during these gaps in protection that infection can get hold.
Chemical controls for summer diseases really gives a good snapshot of the current state of the industry and how registered control products fit. We’re seeing a changing picture for control products – moving towards more target specific, reduced risk products but also seeing limited options whether that’s chemical group alternatives or restrictions on use. We’re also seeing resistance concerns because many of the products available are single site or high resistance risk products and continued use can select for pest populations that are resistant. So, sprays need to be precise and they need to be strategic. Make use of other control strategies, monitor and consider appropriate action thresholds to supplement reliance on chemical control.
Cassie: Yeah, can’t highlight enough that every successful IPM program uses all of those different technologies and doesn’t heavily rely on just one, like chemical controls because that’s when we get resistance issues.
Kristy: Yeah, for sure.
Cassie: Ok, so we’ve talked about pest prevention, understanding pest biology, monitoring and using thresholds to help determine control timing, making use of multiple control strategies, is there anything else that’s involved in an IPM program?
Kristy: Yes, what I consider one of the most important but often overlooked elements of IPM – evaluation. How do you know what worked, if you’re not evaluating it? Growers are busy and they spend a lot of their time moving from one task to the next, so it is really easy to continue doing what they’ve always done. But it is important to take time to get feedback on your program so that you can adapt to changes as they arise. This is information can be used in the short-term to determine if your management strategy was effective as well as for a record-keeping system to establish trends or patterns in your operation which will help with plans moving forward in future years.
Cassie: Alright, so I know this will be tricky, but if you could sum it all up into one or two sentences or key take away points to a grower trying to use more IPM strategies, what would you say?
Kristy: That’s a really good question. What I think is important to know is that it’s best to take baby steps. Don’t try to change your practice all at once. Don’t try to take on these really huge changes right away. Try just little changes. Maybe one per year and see how it goes. Find what works for you. A lot of times we see someone try to take on something and it’s just too much too soon and dropped quickly. But if you go at it slowly and find ways to integrate things that fit with what works for you in terms of labour, cost and if you’re actually seeing the benefits of what you’re doing.
Cassie: And you’ll only know if you have benefits if you’re evaluating! Maybe you made a good case for that.
This has been a great case study specific to apples but also in general getting to know more on how to use IPM strategies in your production practice.
Kristy: Yeah, it’s really looking at the big picture and how many ways can you manage this pest.
Cassie: Well, thanks Kristy. This was great!
Kristy: Thanks for having me!
Cassie: That was Kristy Grigg-McGuffin, Horticulture IPM Specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs.
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Cassie: Thanks for tuning into our episode today. This has been Cassie Russell -
Kristy: - and Kristy Grigg-McGuffin, for the What’s Growing ON podcast. For more information on horticulture grown in Ontario, check out the links to our fruit, vegetable and specialty crop blogs in the show notes.
Cassie: Special thanks to Kristy for wearing two hats this week; cohosting and being our guest for this week’s extended episode.
And as always, a big shout to Michael Pupulin for the editing of our episodes. Music from this episode is the track Aspire from Scott Holmes.
Kristy: We will be back soon with an all new episode of What’s Growing ON. In the meantime, if you have questions, comments or suggestions for a topic you would like us to cover, Please send us an email us at ONhortcrops@gmail.com. We would love to hear from you.