July Newsletter - Common Nutrient Deficiencies and Work on the Go!

 Upcoming Events

• TunnelTalk (virtual webinar series taking place at 12:00 pm AST)
• July 6 - Virtual Office Hours
• Bring questions, comments and queries to discuss with myself and your peers! These sessions are all yours to chat about all things protected production
• Link to join - Join from Zoom Workplace app - Zoom
• Passcode - 682082
• July 20 - Virtual Office Hours
• Bring questions, comments and queries to discuss with myself and your peers! These sessions are all yours to chat about all things protected production
• Link to join - Join from Zoom Workplace app - Zoom
• Passcode - 480901
• August 10 - Virtual Office Hours
• Bring questions, comments and queries to discuss with myself and your peers! These sessions are all yours to chat about all things protected production
• Link to join - Join from Zoom Workplace app - Zoom
• Passcode - 353572
• TAILGATE - Cover Crop Demos in Hort Crops 
• July 20 @ 5 pm, South Brookfield (registration coming soon)

Demonstrations and Trials on the Go

I don't typically get around to talking about demonstrations/trials that I've got on the go until they are done, but I thought I would give you a bit of a teaser of what's coming down the pipeline!

On Farm Climate Action Fund - Cover Crops and Phosphorus Mining

Most tunnel growers are quite familiar with what happens to phosphorus levels over time...always on the up and up! I came across a paper a year or so ago talking about how different cover crop species have differing abilities to take up phosphorus from our soils, and thought that would make an excellent demonstration for our protected production community here in Nova Scotia. David and Cindy and Pleasant Hill Farm have agreed to host this for me for a few weeks this summer, and this is one of the stops we will be looking at for the tailgate meeting coming up!

Low Tunnel Everbearing Strawberry Production

Following our berry tour of Ile d'Orleans last September, one of our local strawberry growers has decided to give low tunnel production a try! Their latest batch of everbearing strawberries were planted this spring, and placed under low tunnels. 

It was interesting to hear about the rationale of using the tunnels in Quebec - it was less about season extension, and more about producing a high quality berry and reducing disease pressure that results from rainfall. The impact of rain exclusion on soft fruit is significant, but high tunnel costs are a significant barrier to entry for most. Low tunnels are quite a bit more affordable, and offer some of the benefits that a tabletop operation would give.

We will be tracking a few things along the way - looking at how the growing environment differs from an exposed bed of everbearing strawberries (temperature, humidity, soil moisture and soil temperature as well), as well as how our management changes. The tunnels are going to be lowered for rain events, then lifted back up once things clear up. This is a labour intensive practice, but the grower we chatted to in Quebec swears by it! He's been using this system for 15 years and has found that the input costs are well worth the quality of the berries coming out the other end. If you want to revisit our tour of the farm, check out our video summary! You can jump to Fio's farm at 1:07:14. 

I'm excited to follow this low tunnel trial in Nova Scotia over the next two years, and evaluate the potential for this type of production! Stay tuned!

Sensor Installation for Tunnel Structure Comparison

I'm excited to be exploring opportunities to showcase how high tunnel structures compare to one another in terms of growing environment and management strategies! I'm really hoping to focus on some of the tech options we have available to us to help manage these structures as well, and showcase the impact they have!

The details are still being ironed out on this, but I have my sights set on showing you things like internal temperature and humidity on structures with ridge vents versus roll-up sides, the impact of shade cloth and/or whitewash compared to a more transparent structure, as well as the difference between tall structures and short structures. I hope you like thermal images and graphs because we have a LOT of data coming your way!

Managing Crop Fertility

Now that our plants have been in the ground for a few months, we can start to see some funky stuff crop up. I'm hoping this post will give some tools on how to figure out what our common nutrient deficiencies look like to make it easier to supplement the right fertility and get back on track. 

First off, let this serve as a gentle reminder for folks who are doing split applications of nitrogen through the season!

We've been talking a lot about nitrogen management planning these last few years, and how we can combine the practice of front-loading fertility with split applications in season. This is a great blend of nutrient delivery strategies that will help to feed our crop all season long. Based on the first few weeks of June where we had prolonged cool temperatures, I would expect that our slow-release amendments may be a bit behind in the break-down compared to the last few years. When that mineralization is compromised, plants are not able to access all of the nutrients that they need, and you'll notice that the older leaves will start to turn yellow. This is where coming in with a soluble application of nitrogen is really handy! We can recognize that the release process is much slower than it will be in September and October, so its the perfect time to supplement readily available food until we can feel more confident that our preplant amendments are breaking down.

For folks who did apply a preplant application of nitrogen, we want to take the amount of remaining nitrogen that our crop requires and divide it by the number of weeks we want to supplement (once a week until the end of August would translate to 8 weeks), and then by the number of times we are able to run it through the drip (ideally 2-3 times a week). 

I really like this table from the New England Vegetable management guide. It breaks down our nitrogen requirement based on your yield goal/what you are typically growing per square foot. Take a look at that 'N Need' category, and that is your total over the entire season. 

Table 1. Recommended N application rate based on yield goal. This screenshot was taken from the New England Vegetable Management Guide (https://nevegetable.org/crops/tomato-greenhouse-and-high-tunnel)

We certainly can't forget about Potassium

Signs of deficiency to look for:

• yellow shoulders
• hard white pith in the fruit 
• tip and marginal leaf scorch
• chlorosis throughout the leaf
• reduced fruit size

Potassium for ripening tomatoes is crucial and the deficiency can creep up on you. Our soil tests are typically reporting that we have an abundance of potassium in soil-based high tunnel tomato production, but our fruits are still turning up like this. In my experience, that is usually the case when we also have excess levels of calcium and magnesium in our soils. Calcium has a stronger hold on our soil particle surfaces compared to magnesium and potassium, and therefore it can interfere with the plant's access to these nutrients that are lower on the chopping block. 

My recommendation for folks that are primarily supplementing nitrogen in soil-based systems is to start supplementing potassium through the drip this time of year. This will make it a bit more accessible for the plant to take up, and should help to counteract the signs of deficiency. I like to start feeding it through the drip this time of year, now that we have active fruit set and ripening happening. Potassium sulphate is a great option and should be readily available to you. 

Next up is Magnesium

Signs of deficiency to look out for:

• stiff, brittle leaves
• upward leaf curl
• chlorosis between leaf veins

Magnesium is the center molecule in chlorophyll, meaning this is an important accomplice to nitrogen for a healthy and productive plant. Similar to potassium, magnesium can be overshadowed by an abundance of calcium in protected soils, so this is another nutrient that I like to see supplemented in season. 

Epsom salts are a great way to put magnesium in through the drip. It doesn't have to be there for every watering, but I think prioritizing this addition every 3-4 weeks will keep those leaves beautifully green. Now is a great time of year to start feeding some magnesium to your soil-based crops if you haven't already done so.

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If you find that you are seeing symptoms on your plants but they don't quite fit the bill of nitrogen, potassium or magnesium samples, Perennia has a great Nutrient Deficiency guide that you can access here. Pay attention to where the deficiencies will show themselves along the plant, and that can help point you in the right direction. If you are seeing the discolouration through the whole crop, that's a good indication it's a nutrient or environmental stress. 

Don't forget that tissue testing is also an option for figuring out the root cause of our leaf symptoms! I really like in-season tissue testing, because it serves as an evaluation of the plan that we put together in the winter. Are the amendments behaving the way that we think they would? Are the supplemented nutrients being taken up by the plant? 

These results are a great way to get in-season feedback on our split nutrient applications. If I'm sitting 10% over the target for nitrogen based on my plant stage, then I will start to dial my weekly amount of nitrogen back as well. It makes absolutely no sense to provide additional fertility than the crop needs, and this is a great way to quantify what those needs are. 

Check out our landing page for the analytical lab to get pricing, submission forms, and information on how to tissue sample. There are many reference tables available on the internet as to what our target numbers should be. I really like tables that take plant stage into account, for that added edge of crop steering and making sure we are supporting plants with a heavy fruit load. 

Pest Management Resources

It can be very difficult to sift through all of the biological-based products that are commercially available and know which ones are going to work for you! I came across some efficacy tables put together by Koppert in last month's edition of GrowerTalks magazine, and figured I would share that here with you! I like that each line item includes information on how the product can be applied, the use sites (greenhouse vs outdoor nursery production vs landscape), and all of the issues that are controlled by each product. It also comes with an activity rating, which is information that can be very hard to come by! I can't speak to how these were all evaluated, but I think this is a great starting point when we are having to make decisions on what products to use compared to others on the market. 

I was unable to upload a legible copy of either of these, but the link to the virtual version of this chart is linked in the table description, as well as the image. 

Table 1. Common biofungicides used in floriculture and nursery in the U.S. and their target diseases. The + symbol indicates some activity, +++ indicates high activity. Taken from GrowerTalks Biosolution Guide 2026. 

Table 2. Common bioinsecticides used in floriculture and nursery in the U.S. and their target diseases. The + symbol indicates some activity, +++ indicates high activity. Taken from GrowerTalks Biosolution Guide 2026. 

That's all I've got for now folks! Happy growing, and don't hesitate to reach out with any questions. 

Cheers!

Talia (tplaskett@perennia.ca)

June Newsletter - Tomato Pruning and Managing Summer Conditions

 Upcoming Events

• TunnelTalk (virtual webinar series taking place at 12:00 pm AST)
• June 2 - Considerations for Protected Production
• June 14 - Virtual Office Hours
• Bring questions, comments and queries to discuss with myself and your peers! This session is all yours to chat about all things protected production
• July 6 - Virtual Office Hours
• Bring questions, comments and queries to discuss with myself and your peers! This session is all yours to chat about all things protected production
• TAILGATE - Cover Crop Demos in Hort Crops 
• July 20 @ 5 pm, South Brookfield (registration coming soon)

Production Tidbits: Pruning Matters!

As our tomatoes are taking root in our tunnels, it's worth starting to wrap our minds around pruning strategies for the year! I usually like to do my first light prune on tomatoes once the second cluster is upon us. Once the third flower cluster is ready to rock, I'm starting to fall into my routine for the season. 

Tomato pruning on indeterminate varieties has a lot of benefits for the plants and the quality/size of the fruits harvested. While it is crucial for managing the energy resources within the plant, as well as managing pest and disease outbreaks, it also has implications on our fruit production and ripening. 

Figure 1. Three images of sunscald on tomatoes. Photo credit goes to the University of Florida IFAS.

I was able to take a thermal camera out and about last year, and captured some interesting images on fruit temperature. Fruits that were fully exposed to the sun were significantly hotter compared to those that had some shade from overhead leaves. These photos were taken in the same area of the greenhouse within a few minutes of one another.

Figure 2. The king fruit on an exposed cluster of cherry tomatoes, reading 29.5C on the thermal camera. Photo credit Talia Plaskett

Figure 3. The recorded temperatures of two tomato clusters under the shade of the overhead canopy. Photo credit Talia Plaskett

Developing fruits are sensitive to the sun. Our pruning strategies for tomatoes can either help us, or hinder us. Here is a quick look at my general rules of thumb for pruning slicers:

1)For every one tomato/flower cluster, I want to have 2 fully expanded leaves on the plant. For example, a plant with 4 fruit/flower clusters means I want to see 8 fully expanded leaves. A plant with 6 clusters is going to require 12 leaves. I typically do my leaf counts starting from the bottom of the plant and working my way up to the growing point.

• Less than 2 leaves per cluster means that the plant may not be able to generate enough energy to sustain a high yielding plant through the full growing season.
• More than 2 leaves per cluster means that the plant will be more likely to hang out in its vegetative state. Vegetative states favour leaf production over fruit production, which doesn't help us much when it comes to harvest and having produce to sell. 

2)When choosing which leaves to remove, I don't exclusively remove from the bottom. While that does become the usual place to remove leaves, there's a bit more to the story:

• The top of the tomato plant is actively responding to the conditions it is experiencing at the time. This will influence the number of leaves between clusters, as well as the thickness of the stem. If our variety is consistently putting out two leaves between each flower cluster, sometimes you will see one leaf and others you may see three or four leaves between each cluster. When we start to see these sections of higher density leaf canopy between clusters, this can be a good place to include in our thinning efforts. By managing the canopy density along the length of the tomato stem, we can reduce the likelihood of disease issues in higher density spots.

3)As much as we are managing the canopy along the length of each tomato stem, it's also worth looking at the bigger picture, and managing the density of plant leaves from adjacent plants. There will always be sections of the tunnel where the canopy seems to have higher density spots compared to others. When I'm deciding which leaves I want to remove as I look up a tomato stem, I do try to take the leaves from the neighbouring plant into account. Trying to maintain a more even canopy through the production space is an important strategy for managing humidity, airflow, and disease pressure as well. 

As a general rule, I don't like to remove more than 3 leaves at one time. It needs time to adjust to the new source (leaf) and sink (fruit) dynamics as to not completely throw off your harvest schedule. If you did get a bit behind, just approach it with removing 3 leaves a week, for as many weeks as it takes to catch up to where you want to be. 

Ideally pruning is going to happen early in the morning. We want the wound to dry up as much as possible before night time. Evening temperatures typically drop, causing condensation/humidity to spike which leads to disease pressure if left unchecked. If we are pruning in more wet/overcast conditions, either wait until another day in the week to tackle the project, or get it as early on the schedule as possible for that day, maximizing the time for the wound to dry out. 

Seasonal Considerations: Managing Summer Heat and Humidity

May brought us some HEAT mid month, so let's talk a bit about how to manage those things before it comes more consistent! Protected production is unfortunately a highly interlinked production method. We have many variables that we want to work nicely together in order to get that peak production. It quite a balancing act...but that being said, I think understanding how things are working together is half the battle!

IRRIGATION

First step is obviously going to be irrigation. Plants require water to photosynthesize. The more sunshine available, the more the plant has the capacity to be photosynthesizing...so we need to make sure that there is enough water available for plants to do what they do best. I completed a 2 part webinar series with Jacques Theriault from Climax Conseils in the spring, so for those of you who want to revisit those recordings, you can find them linked here:

Irrigating High Tunnels pt 1 
Irrigating High Tunnels pt 2

These sessions focus on how to dial in your irrigation schedule in order to best support your soil-based crops. At the end of part 2, Jacques did a quick summary of some of the ways that plants can show their irrigation stress, which I thought was a great tool for us this time of year, so you can find the shortened version of that video linked here: Irrigation-Linked Symptoms in High Tunnel Crops.

TEMPERATURE

Mother nature has already flexed her muscles this year on just how warm it can get in a tunnel, and I have a feeling it is just the beginning! Where we aren't actively cooling our protected spaces, we do have a few tools we need to be using to try and manage indoor temperatures. Pollination and plant productivity do start to slow down depending on the crop. Protected strawberries, for example, don't love temperatures over 24C. Tomatoes tap out around 27 or 28 degrees (mostly in terms of pollination success). 

While we can't control the sun, we can play around with reducing the intensity of the sun coming through our greenhouse. Shade cloth and whitewash are great strategies to reduce the amount of radiant energy coming into the greenhouse. It diffuses the light coming in, and reduces the heat that enters the space. I've opted to stand inside a whitewashed- tunnel on a hot August day as opposed to out in the full sun...these tools can be incredibly effective to reduce temperature indoors!

Whitewash is applied one time via brush, roller or spray, and is then left for the season. The product purchased is meant to be diluted with water, so you get to decide the degree of shading you want to get with each application. There's a bit of unknown as to how the summer is going to flesh out, but this is quite easy to apply and then it's not something you have to worry about. You could always start with a lighter layer and come in behind it with a second coating if you're finding there's still a bit too many rays getting into the tunnel. The product is said to come off through the fall and winter with precipitation, but for those of you who are wanting to do winter production, there is a cleaning product you can purchase to help get that whitewash off earlier and you can rest easy there will be no light blocked when it starts to become limiting again in the fall. 

Shade cloth does give you a bit more flexibility to put it on and take it off as the season progresses, but keep in mind that it isn't the easiest thing to put up and take down. It requires a larger crew, and a low wind day. It would cost more compared to whitewash, but then you are left with a physical barrier that can be used year after year if cared for properly in the off season. You are also committed to the level of shading that you purchase at one time - each cloth is obviously set at the level of shading that it comes in, and can only be modified by grabbing additional cloth.

Figure 4. Strips of shade cloth installed over a double poly high tunnel. Photo credit: Talia Plaskett

Even if this isn't something you have used before, I highly recommend just having it on hand! I've seen quite a few lost crops due to sunscald in the last few years, and it's worth being prepared to have to manage this as our growing seasons change and evolve through time. 

HUMIDITY

I'm planning to do a few more specific webinars on humidity...but for the time being I want to keep it short, sweet and hopefully helpful. 

As a region with a tendency for very high humidity, we have to be extra careful to manage our protected spaces. The driving force for plants taking up water from the soil is the differential between the water in the leaf tissue (100% humidity) and the surrounding air humidity. 

• If we have a high tunnel humidity, the speed that water is being pulled from the plant is very slow. Where water moves from high concentration (in the leaf) to low concentration (surrounding air), having a small difference is going to translate to a slow speed. This will slow photosynthesize, and the plant's ability to cool itself. Consider it like sweating on a hot day- a light sweat isn't going to regulate our body temperature nearly as well as a more steady sweat.
• If we have a low tunnel humidity, the water will be pulled from the plant very quickly. There is a speed that is too fast, where mineral and sugar transport through the plant is impacted and the plant isn't able to really use the water in the way it needs it. The plant will need much more water, and is prone to 'dehydrating', if we want to continue with my sweat analogy

While we can't really reduce the air humidity, we can make sure that our air is moving. Creating an air current will at least force some water movement out of the plant. How do we do this?

1) Venting. Make sure that we are actively venting our tunnels to help flush out the hot humid air that gets trapped in our tunnels. Ridge vents are the most effective at dumping humidity. Roll-up sides work well, but we also need to consider that hot wet air that rises up into the peaks of our spaces. Having end-wall vents high up in the peak is pretty important for dumping that humidity

2) Air circulation. We want to see air movement within the tunnel, as well as being exchanged with the outside air. For air circulation, horizontal airflow fans are the best tool for that. We want fans pointed in a way that encourages the air to move in a continuous circle around the greenhouse. We should have one pair of fans every 50ft or so. The goal is to move about 1/4 of the greenhouse air every minute. This will look like a flutter in our leaves when it's done properly. 

As for our target humidity, it isn't as easy as saying 'this one number and that's it.'! Our target humidity is going to depend on the air temperature in the tunnel. I've attached a reference table here below from Perennia's long cane raspberry guide. Check where you are at temperature and humidity wise, and see how you are doing! The green zone is ideal for the plant water balance, yellow is challenging, and red is to be avoided. 

I am more than happy to talk about managing our tunnel growing environments, so please don't hesitate to give me a call if you want to chat about this. I'm planning quite a bit of extension around this topic in the next few years, so hopefully we can demystify some practices and really start dialing in our tunnel spaces for optimizing production efficiencies and maxing out harvests. 

Happy Growing Everyone :)

- Talia 

May Newsletter: Monitoring pollination and biosecurity considerations

 Upcoming Events:

• Tunneltalk Webinar Series
• May 4 - Enterprise Budget for High Tunnel Tomatoes
• June 1 - Considerations for Protected Production
• June 15 - Virtual Office Hours
• July 6 - Virtual Office Hours
• July 20 - Virtual Office Hours
• August 10 - Virtual Office Hours

Production Tidbits: Monitoring Pollination

While tomatoes can self pollinate, there is a lot to be gained from supplementing bumblebees into tunnel houses, especially for early season tomatoes which flower well before natural pollinators are out and about. Tunnel hives increase the consistency, quality and size of the fruit on the truss. It can also impact your harvest time- rather than having slow, inconsistent fruit set that ripen at different times, we are able to help that along and harvest the fruit on a cluster in a shorter window when the flowers are well pollinated right when those blooms open.  

When it comes to pollinators, we may have quite a few buddies buzzing around, but that doesn't necessarily mean that they are visiting the flowers. Pollination compatibility is highly dependent on flower structure, so what works well for one type of plant may not necessarily work well with another! 

Regardless of whether or not you supplement hives, we are able to monitor the degree of visitation happening to your solanaceous crops. 

The anther cone, which is the little bit that sticks out in the centre of our petals, has little signs of bumble bee visitation. 

    1) We see some darker orange flecks on that anther cone.

    2) No flecks translates to no/low visits from bumble bees

    3) A fully dark orange/brown anther cone means the visitation is much too high, and/or the tunnel is too humid. High humidity causes the pollen to stick together, and making it much harder for our worker bees to pull out the good stuff. 

We can respond a few ways depending on what we are seeing:

    1) A few bite marks is great! Everything is progressing as it should, and we can check back next week to make sure that the current rate of pollination is maintained

    2) Consider ordering a supplemental hive for your greenhouse. If you already have one, contact your hive supplier on trouble-shooting measures, or to assess whether its time to replace what is sitting in the greenhouse

    3) We have a few options for this one: 

• Close the hole on your hive part way, to reduce the flow of traffic out of the hive temporarily. Give your crop a few days to recover, and then allow the bees to stream out again.
• If this is a high humidity situation, we want to try and remedy that BEFORE closing the  hive off to the crop. Open up the vents (end, side or roof) and turn up your ventilation fans to get that air moving out of the tunnel. Once things are back in balance, expect to see less damage to the anther cones on your tomatoes.     

Want more information on this? Check out the recording of one of our previous webinar sessions focused on pollination- Tunneltalk Webinar: Pollination

Seasonal Considerations: Order of Entry Around the Farm

Biosecurity protocols are going to be one of the best preventative tools we have to reduce disease and insect pressure inside our greenhouses. Whether your farm is big or small, there are a handful of practices that can be incorporated relatively easily on farm to try and make that path to entry a little bit harder for pests who were not invited to the party. 

Here are a few considerations around order of entry to start the season off to the right foot:

1) The tunnel should be visited FIRST (and not just because I like tunnels)

Anyone who is growing transplants, or planning on growing plants indoors and outdoors, is at at risk of transmitting field pests and pathogens into our greenhouses/tunnels. This can come in on our boots, our clothes, growing tools, or anything that we are bring from outside the space. Whenever we can, we want to visit the 'clean' spaces before we hit up the 'dirty' ones.

2) If we do need to visit the greenhouse multiple times throughout the day in between field tasks, there are a few things we can do:

• designate one (or more) person to be responsible for the greenhouse space, to limit the crossover
• have greenhouse-specific footwear that does not leave the greenhouse. Outdoor shoes stay outdoors, indoor shoes stay indoors
• have greenhouse-specific clothing. This can be a coverall, or a completely different set of clothes. 

For those with multiple tunnels, there are a few more layers to this:

1) plan to visit the tunnels from order of age: youngest --> oldest throughout the day. The young plants are going to be the most susceptible to pest and disease damage compared to older ones, so we want to preserve their health as long as possible

2) if we DO have signs of diseases or pests cropping up, then we are going to plan our day in order of cleanest to dirtiest. Infested/infected houses will be towards the end of the day, and the clean houses should come first.

Just like plants, insects and diseases really love protected spaces. High humidity and temperatures really help problems to thrive, and if they can find a way into our protected spaces, they will. All we are trying to do is make it a little bit harder for them to get into the greenhouse. 

Pest and Disease: Transplant and Early Production Oddball

Springtails! 

Photo pulled from Cornell and UConn. The red circled insects are winged aphids, to show how they compare in size and shape to springtails on a yellow sticky card. 

Springtails are a bit more under the radar when it comes to spring pests...but after a report of some damage caused by these buddies earlier this year, I figured they earned their spot on this list. They have been occasionally reported feeding on beans, beets, broccoli, potato, radish, cucumber and greens across the northeast. 

This tiny insects typically feed on decaying plant material and for the most part are seen as beneficial insects. In some instances, however, they will feed on and cause significant injury to young plants. The damage and appearance of these guys looks very similar to flea beetles. They spring away when a plant is disturbed, and are most problematic to young plants in the spring. The main differences from afar are going to be those host crops, as well as the size - springtails are about half the size of a flea beetle. 

Eggs are laid in moist soil with high organic matter....so if you do see them out and about in your greenhouse, anticipate that they will likely crop up again next year. These can be controlled using insecticides, as well as a combination of beneficial insects. 

Recent Uploads:

• Irrigation-related Symptoms
• Irrigation in High Tunnels part 1, ft Jacques Theriault, Climax Conseils
• Irrigation in High Tunnels part 2, ft Jacques Theriault, Climax Conseils

April Newsletter: Project Summary - Assessing the Efficacy of Disease Protectants Against Pythium

Alright folks, this will be my last project update for a little while! That was a whirlwind of information, but I hope that you were able to take the time and read through the work over the last few weeks.

As we are right on the cusp of April, I figured I can share a few upcoming events and other newsletter updates alongside this post as well. Based on the size of this list, we are officially transitioning out of event season, and transitioning into the growing season! 

 Upcoming Events/Perennia Updates

• Tunneltalk Webinar Series
• April 7 - Irrigating Soil-based Crops in High Tunnels (pt 2)
• check out the recording for part 1 here if you haven't already!
• May 4 - Enterprise Budget for High Tunnel Tomatoes

Recent Project Work: Assessing the Efficacy of Disease Protectants Against Pythium

Based on the varied and inconsistent disease results we saw following anaerobic soil disinfestation (ASD) implementation on farm, we decided to dedicate some of our project funding through Horticulture Nova Scotia to assessing the efficacy of some of the commercial root protectants that are available on the market. We have a wide host of products with notable price tags, looming expiration dates, and a lot of uncertainty on efficacy...so this seemed like a great opportunity to try and add some clarity on what is available on the market, and what these products can do!

Figure 1. Disease-susceptible tomato seedlings germinated in diseased soils. Photo credit: Lindsay Scott

In a perfect world, we would be able to implement this project in a commercial greenhouse, dose certain plants with disease, and follow a handful of plant productivity metrics over time gaining valuable information on what each product was able to offer in terms of protection. This is just not feasible with our current resources. We went back to the drawing board to see what we could pull off, and landed on a tomato seedling assay. This way we are able to test the products in a 'living' situation, while addressing our space restrictions and desire to keep inoculated trials contained and far away from commercial production. You can see the project setup below in Figure 2. 

Figure 2. Plant rack setup used to evaluate the efficacy of biological root protectants. Photo credit: Talia Plaskett. 

I wanted to assess product efficacy in two scenarios with these trials:

1. Seeds are planted into infected media with and without preventative products applied
2. Healthy seedlings are transplanted into infected substrate with and without preventative products applied

Both scenarios give the plants 3-4 weeks of growth in their respective treatment, giving the disease some time to take hold and lend us some information on product efficacy. 

Due to the sheer number of products available for biological control of Pythium root rot, we decided to focus on representation of active ingredients as opposed to each individual product on the market. We settled on a list of 6 active ingredients to test in our growing rack, one of which serves as a conventional chemical control. Each product is applied preventatively according to the label recommendations throughout the duration of our trial. 

The active ingredients we decided to include are:

• Trichoderma harzianum
• Streptomyces lydicus
• Gliocladium catenulatum 
• Bacillus amyloliquefaciens
• Mono- and di-potassium salts of phosphorous acid
• Propamocarb (conventional chemical control)

The main metrics we were observing through the trial was root development and root disease, however we took notes on percent germination, wilt, and vigor on the seedlings as well. Figures 3 and 4 showcase healthy plants compared to diseased ones to provide context to our rating systems. 

Figure 3. An example of a healthy seedling on the top of the image, compared to the seedling on the bottom which is experiencing disease symptoms on the root and lower portion of the stem. Photo credit: Talia Plaskett

Figure 4. The root ball of a healthy tomato seedling (right) compared to the root development observed on a diseased tomato seedling (left). Photo credit: Talia Plaskett

So what did we find? Figure 5 outlines the disease symptoms observed on plants that were direct seeded into diseased growing medium. I wanted to mimic what might happen if we are starting plants in dirty seeding trays, irrigating with water that may contain fungal spores, and/or the media was contaminated somewhere between our last use of it, storing for the season, and bringing it back out for the spring. 

The plants were scored from 1 (assigned to plants with roots that are disease free and well developed) to 5 (assigned to plants with high disease severity and poor development). If we start out by looking at our water control, we did have some underlying disease showing up even though the plants were not inoculated. My guess is that came from the water that we used to irrigate the entire trial with. If we take a look at the results we can see that there is a difference in the degree of protection offered to the plants depending on the active ingredient. The taller blue bars indicate more disease compared to short blue bars. We also see some significant differences in the amount of root development observed: the shorter green bars are more representative of what I would like to see for root development compared to the taller bars which had very poor root development. 

Figure 5. A graph outlining the root development and root disease across inoculated, disease susceptible tomato seedlings. Credit: Talia Plaskett

A few noteworthy take-homes:

• Plants treated with Trichoderma harzianum had better root development compared to plants that were treated with our conventional chemical intervention.
• Plants treated with Trichoderma harzianum had the lowest disease incidence across the plants that were inoculated with our Pythium cocktail. 

As the second part to this experiment, I wanted to see how the products performed when disease was introduced at transplanting. Healthy plants were transplanted into 4' pots after receiving preventative treatment since seeding. These pots were then inoculated with disease, simulating the transplant of healthy seedlings into a diseased soil. 

Figure 6. A graph outlining the root development and root disease across inoculated, disease susceptible tomato seedlings. Credit: Talia Plaskett

This assay proved to be a little bit trickier to make judgements on! If we look at the plant health rating on the y-axis of Figure 6, you'll notice that there isn't a very large range here. Plants scored between 1 and 2 across the board, making it hard to tease apart significant differences across treatments. I would say this is largely a result of the time we were able to run the trial - the plant rack did not have enough space between each level to support the plants growing taller than they were at assessment, and now that the plants are a bit more established, the root disease we introduced didn't have enough time to really get going compared to the seedling assay. 

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I would love to hear feedback on your experience using these products to protect against root disease through a full season of production! I'm hopeful one day we can repeat this work in a more commercial setting, so fingers crossed that is a possibility in the future! And hopefully the results that we were able to generate here give you a bit of a leg up on what active ingredients you want to try on farm compared to others. 

I still believe that these products offer a leg up in terms of root development and ability to withstand disease pressures in our highly sought-after high tunnel soils, so I do recommend adoption where possible to give our crops their best chance at success for a long season ahead.  

Seasonal Considerations: Pollination!

I am a bit early to the punch here talking about pollination considering most folks aren't putting out their tomatoes yet...but I want to get the ball rolling, and remind you about the webinar we did a few years ago talking about pollination! Remember that our native pollinators are typically not active and ready to go when we are transplanting our tomatoes into the high tunnel, so purchasing a hive to correspond with the timing of our first flowers opening can guarantee a beautiful, early and consistent fruit set across the production space. 

You can access the recording of that session here.

Terminating Winter Cover Crops

Recent Project Work: Winter Cover Crop Termination Demonstration - Funded by the On-Farm Climate Action Fund Program

Our March madness of winter work continues! The second demonstration that I'd like to talk about this month is funded by the On-Farm Climate Action Fund (OFCAF) program. For this work, I wanted to focus on the efficacy of different termination methods for winter cover crops. 

Why Cover Crop?

Before I dive in to the demo itself, I wanted to talk a little bit about why we might want to cover crop our protected spaces through the winter. This list is specifically geared to folks who are not producing winter greens, and have empty tunnels during the winter months. For those who are growing cash crops through the winter, cover cropping may be better suited to other times of year where cash crops are not being produced.

1) Support soil structure in intensively cropped soils

High tunnel soils are the most intensively used on the farm, so the growth of low-feeding, low maintenance crops through the winter can help to support aggregate stability in our soils and prepare them for the next round of summer cash crops. Where erosion is less of a concern in high tunnel spaces, plant roots work wonders on soil structure and their ability to hold water for the following year. 

2) Support microbial communities following our summer cash crops

Our soil microbial communities require a food source in order to maintain their populations. While metabolic activity will slow in the winter, it doesn't stop completely in a protected space. Growing cover crops in the greenhouse through the off-season provides a steady flow of root exudates into the soil, which are a great food source to support our microbes. This means that come time for transplant, our microbial population is going to be much stronger and much more active right from day one, compared to a fallow greenhouse which will 'wake up' in response to the introduction of plant roots. For more information, check out this article from Penn State.

3) Weed suppression before we come in with our spring transplants

Once February and March roll around, it is fair game for any and all plant life that could be surviving in the high tunnel. Having a well-established cover crop in place provides competition for weeds that are trying to establish in late winter/early spring.

4) Help to generate organic matter in the greenhouse

For those who do not grow winter greens, protected spaces are usually left fallow for the winter. Why not take this opportunity to grow plant material that can help to build organic matter in your greenhouse? Where our best management practices (BMP) surrounding nitrogen use are leaning towards pointed nitrogen application and less towards regular bulk additions of compost in high tunnels, we can look to other practices to support organic matter generation. 

5) Soak up residual fertility left over from our summer cash crops and turn it into biomass that will hold the nutrients in a more stable form

Certain nutrients, like plant-available nitrogen for example, are quite prone to loss if there are no plant roots around to take it up. Planting a cover crop following your summer cash crop is a great way to take advantage of residual fertility hanging out in the soil, and convert it into plant tissue...a much more stable form! Once it comes time to terminate the crops, we can return those nutrients back into the soil to feed our next round of cash crops, making sure none of our valuable added fertility goes to waste. 

Figure 1. The soil observed in our cover crop termination demonstration in December. Photo credit: Talia Plaskett

 

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Through the OFCAF program, we have already demonstrated the impact of planting dates, as well as the impact of row cover for supporting winter cover crops. For this winter, I wanted to talk a bit about how we manage this winter cover crop in the transition to spring cash crops. 

Winter cover cropping requires specific selection of species that are going to withstand winter conditions in a high tunnel. Combining these winter-hardy species with row cover to help buffer the lower temperatures of the off-season leaves us looking for other methods to terminate cover crops in time for our spring plantings. Organic and regeneratively-minded farms do not have the reliability of spraying out cover crops, meaning they are more prone to survivorship in cover crops once they have been terminated. 

For this demonstration, we are showcasing the efficacy of flaming, mow + flaming, mow + incorporate, tarping, and winter kill on their abilities to terminate a winter cover crop of oats and peas. Due to the variable nature of high tunnel production across the province, we will terminate on three key dates - December, end of January, and end of March. These are representative of times where we may be transitioning over to new crops, and I wanted to showcase any headaches or differences in efficacy of these termination methods as a result of termination date. 

The full list that can be found on site includes:

    December termination

        -flame

        -mow + flame

        -mow + incorporate

    late Jan/early Feb termination

        -flame

        -mow + flame

        -mow + incorporate

    mid-late March termination

        -flame

        -mow + flame

        -mow + incorporate

        -tarping

        -(assess) winter kill

There's another piece to this however...how does winter cover cropping termination method impact our cash crop success? Having a high degree of residue left over from our termination methods is going to impact what we can plant in that soil...a direct-seeded green is going to have a much harder time at establishing compared to a tomato transplant in a high-residue bed. The timing of our termination, as well as the method, is going to impact the success of establishing our cash crops, and that was the basis for this conversation on cover crops. 

Once May rolls around, I will be going on farm and documenting weed pressure and cover crop survival in each of our terminated blocks/dates, as well as the amount of residue left on each block, and report back on what we see! I will also be linking each method to a rough cost so that we can be better prepared to adopt this BMP on farm.

We are also going to show the impact that each termination type/time has on our soil microbial health - how does an early termination of a winter cover crop impact our microbial communities compared to one done in March? These results are going to take more time to generate, but I will share them with you as soon as the lab gets back to us with results.

So...what have we seen so far?

Cover crops were maintained under row cover through the duration of the winter to maintain them through the significantly colder temperatures experienced in '25/'26 compared to the last few years! When we pulled back the row cover, the cover crop was quite moist, raising some concerns on the efficacy of flaming, as well as the amount of propane we would need to burn through in order to terminate them. This is where the mow + flame treatment came into play - if we are able to cut up the tissue a bit, will the cover crop terminate better?

Figure 2. Flaming of a section of our winter cover crop with the goal to terminate it completely. Photo credit: Talia Plaskett

Looking at our three termination methods for December, we can see the mow and incorporate treatment on the left hand side of figure 3. In the middle is our mow + flame treatment, and on the right hand side we have our flame only treatment. We have a visible difference in the amount of biomass left between the middle and the right hand side, so I'm curious to see what spring will bring in terms of termination success and ease of planting. 

Figure 3. A side-by-side comparison of three termination methods in December. Photo credit: Talia Plaskett

Figure 4 was taken at the end of January, 5-6 weeks following our first round of termination. It was hard to feel confident that flaming was a successful termination method in the crop because of how wet it was, and how much biomass had been generated at the time. Looking at the photos after a few weeks, however, shows that both methods of flame treatment appear to have been successful at terminating the crop. 

Figure 4. A look at our December-terminated cover crop plots. This photo was taken end of January.  Photo credit: Maegan MacLean.

Did you notice the white stakes in each block in Figure 3 and 4? We decided to track soil temperature and soil moisture to show how it is impacted by the different termination methods. Why do we care about temperature and water content? The associations of both variables on microbial activity, diversity and nutrient cycling are too important to ignore!

Figures 5 and 6 depict the sensor data we collected from our first termination (December) to our second termination (end of January). As we would expect, a soil with a living cover crop is going to be much more buffered against changes to temperature compared to a soil that is exposed. The flame treatment, represented by the orange line in figure 5, left a significant amount of residue behind on the soil. This provides some buffer against temperature changes in the high tunnel but not as much as a living cover crop does. 

Figure 5. A comparison of soil temperature measured across three plots: 1 plot was terminated via mowing + incorporation, 1 plot was terminated via flame, and the third is our 'control' with a live cover crop. 

From a moisture content perspective, the bare soil where the cover crop was mowed and then incorporated into the soil, has the lowest recorded moisture. Treatments with residue, either living or terminated, retain a higher degree of moisture by comparison. The living cover crop showed a much more consistent level of soil moisture over time, whereas the plot where the cover crop was terminated and left on the soil surface is still prone to fluctuation. 

Figure 6. A comparison of soil moisture measured across three plots: 1 plot was terminated via mowing + incorporation, 1 plot was terminated via flame, and the third is our 'control' with a live cover crop.

I'm hopeful that the soil health samples that were sent off to PEI are going to link nicely to our temperature and moisture data...so stay tuned! I'm also very curious to see how these temperature trends hold up from our first round of termination to our second round of termination over the last few weeks. We will be doing our final termination in the next few weeks here and then start to look at some of our other metrics of interest- cover crop survivability, weed pressure, and cash crop success based on leftover residue. I will be updating you all on the work as we wrap up the demonstration, so keep those eyes peeled!