Pests: Time to get out and scout

 

I hope you all are having a good start to the season! As plants are emerging out in the field, and transplants growing in greenhouses are being set out, nefarious forces are emerging too. It’s time to start scouting and making a plan for the inevitable diseases and pests, with all their inbuilt hunger for your precious produce. Here’s a quick list of some common things to watch out for this time of year.

Leek moth was first trapped two weeks ago in the Annapolis Valley. Their first flights should be occurring throughout the province now. They are nocturnal so you may never notice them until the larvae are creating window-pane like damage to your onions, leeks, and garlic. They are difficult to control once they establish themselves, as they live inside of the leaves of onions or will bore their way into the stems of garlic and leeks, making the plants unmarketable. Their presence is relatively new in Nova Scotia but they have quickly established themselves. They generally have two flights here, one early in the spring and another later in the summer before garlic harvest.

Leek moth larval feeding damage on garlic. (Photo: Agriculture and Agri-Food Canada.)

Onion, cabbage, and seed corn maggot. These each overwinter in the soil then emerge in the spring, with cabbage maggot flies appearing first, followed by onion maggot flies, then seed corn maggot flies. We can expect the cabbage maggot flies to start their first flights in a couple of weeks (middle to late May). Emergence happens roughly at the same time as yellow rocket starts to bloom. Generally you’ll first notice the presence of these maggots when transplants start wilting on hot days. This is due to the larvae feeding on roots; plants will eventually die if left unchecked. On a small scale, physical barriers (such as row cover, insect netting, etc) are effective. On a larger scale chemical controls are available to help manage these pests.

Onion maggot damage (Ontario CropIPM)

For those growing in tunnels or seed-starting greenhouses you will start to see thrips, springtails, aphids, and flea beetles emerging soon, or already emerged depending on the specifics of your tunnel setup. Inspect your transplants for feeding damage such as shotgun-like holes on your brassicas in the case of flea beetles, or tiny white spots on leaves in the case of thrips.

Onion thrip damage (Cornell University)

Flea beetle damage (UMN Extension)

While we’ve had relatively good weather for seeding and putting out transplants, the recent cold, dreary, and wet weather has slowed soil microbial metabolism, meaning that overwintering plants like garlic might be showing yellow leaf tips right now. This is most likely due to a slowdown in nitrogen mineralization as soil temperatures reduced. This can be remedied by applying a plant available nitrogen source such as a liquid fertilizer or urea. In addition to reduced mineralization rates, the cold wet weather was an excellent environment for promoting fungi such as Pythium, Rhizoctonia, and Smut.

Damping-off (Pythium spp.) beetroot seedling, (Penn State University Extension)

This is not an exhaustive list by any means, but hopefully gives you a good push to get out and start scouting your crops!

Please reach out to me to discuss any of these pests, or if your crops are suffering for other reasons.

 Happy seeding and transplanting!

Tim (tmorcom@perennia.ca)

Season Extension Enhancement Program 2023

 The Season Extension Enhancement Program is now OPEN!

The objective of the Season Extension Enhancement Program is to help support fruit and vegetable growers who invest in innovative technologies to extend their growing season, adapt to a changing climate and open up new market opportunities.

The program encourages and supports Nova Scotia’s fruit and vegetable producers by providing financial assistance with the following on-farm infrastructure:

• adopting season extension technologies;
• enhancing storage capacity;
• adopting and developing irrigation capacity for field operations.

Eligibility

• Applicants are producers of fruit and vegetables grown and sold in Nova Scotia
• Farming activities must be carried out within the Province of Nova Scotia.
• Applicants must be Registered Farmers in Nova Scotia with annual fruit and vegetable income shown in Statements of Farming Activities in most recent 2 years of submitted Tax Returns (2020, 2021, or 2022)

For more information and details for application, check out Horticulture Nova Scotia's website. Be sure to get your application in ASAP!

Pest Alert: Leek Moth (predates most alliums not just leeks!)

 

The first Leek Moth of 2023 was trapped last week in Annapolis Valley, this is a relatively new pest in Nova Scotia, first identified in 2017. The moth is nocturnal so you may never see it unless you use pheromone traps, but the Larvae can cause widespread damage to all parts of the plant and can be difficult to control once established. The larvae will feast inside of onion leaves, or in the stem of garlic or leeks making observation and subsequent control difficult but dramatically reducing yield and marketability.

Adult leek moth. Photo: David Fuller, University of Maine Extension.

This pest generally has two flights per year with the first in mid to late April depending on soil temperatures. This year’s flight will ramp up in the next week or two. The most effective control is insect netting or a physical barrier to prevent the moth’s ovipositor from reaching any part of your alliums (Lilies also serve as a host for you flower farmers out there). There are chemical controls; however, these are most effective when larvae are small and eggs are present and so monitoring is crucial to ensure correct timing. Please review our allium management guides for current control options.

Larval feeding damage on garlic. Photo: Agriculture and Agri-Food Canada.

Perennia and Agriculture Agri-Food Canada (AAFC), with the support of the NSDA, have been trapping and monitoring Leek moths in Nova Scotia to develop models and further understand this new pest. The first flight occurs from overwintering moths when temperatures reach 9.5 ⁰C (mid to late April), the second flight occurs towards the end of June. Figure 1 below shows the Leek Moths caught in pheromone traps during 2020 and 2022, you can see that there is a general trend of two flights; however, the exact timing changes each year. With the recent investments in weather stations across N.S we hope to turn this data into predictive GDD models so that you can be alerted before any Leek Moths have been trapped!

Figure 1. Total capture of Leek Moth adults in pheromone traps during 2020 and 2022

Please reach out to me if you observe or suspect any Leek Moth damage to your crops at tmorcom@perennia.ca or 902-698-2307.

Managing Nitrogen in Soil-Based, Protected Crops

The first session of our mini-series set the stage on some of the issues we are seeing regarding soil health and long-term resiliency in protected spaces. For those of you who missed the first session, or are interested in revisiting the teachings before building on it in part 2, you can find the full recording here (Managing Nitrogen in Protected, Soil-Based Systems). A summary of some of the information presented is listed below:

One of the re-occurring themes in protected soil production is an accumulation of nutrients, specifically things like Mg, Ca, and K, as a result of large deposits of compost before a cropping season. While these are necessary nutrients for healthy crop production and good quality fruit, too much of a good thing is not always a good thing. Typical supplementation focuses so heavily on achieving a target N value, that a lot of the micronutrients that come along with that N slip by unnoticed.

Not only are we concerned with high levels of certain micronutrients, but also have to be aware of the soil structure itself. One of the soil health indicators we talk a lot about is percent organic matter. While we like to see higher percentages of organic matter, it can come at a cost to other macro- and micro- nutrient availability to the plant when not executed properly. Paying attention to the cation exchange capacity value, or CEC, on a soil test, is important for those who regularly apply compost. While not mentioned in this webinar with Judson, the higher the CEC value, the tighter bond exists between the soil particles and the nutrients, which make it harder to make adjustments to the nutrient composition/balance without significant intervention.

Combine these two factors with the lack of overhead precipitation in tunnels, we see astronomical values of these micronutrients, which are going to contribute to a rising pH, and a significant hinderance on the plant's ability to take up all of the nutrients in the required quantities/balances that the crop needs. Here is an example of the soil test presented in the webinar highlighting this exact trend. The top image highlights a soil that has been supplemented but not to any excessive extent, and the second image highlights how that soil has evolved with continual additions of a compost:

When it comes to the use of compost in protected settings, conducting a compost analysis before application is strongly encouraged, as is yearly soil testing so that we see what is happening in these soils that do not have the same opportunities for drainage as an exposed soil would. Understanding exactly what you are putting into the soil, and how often, is crucial to avoiding buildup to the levels displayed here. Generally when it comes to supplying nutrients to the crop, scenarios that require supplementation are much easier to navigate compared to a heavily loaded and complex soil as what is projected above. The use of fertilizer blends can also contribute to the accumulation of certain nutrients. Consider this - the go-to fertilizer you use in your system is 20-20-20. While that is a great source of nitrogen, your P and K are already very high, and is going to add to the already-existing nutrient load. In soils such as these, single nutrient sources are going to be a much better choice as we attempt to remediate these soils into something that are resilient and will support crop production well into the future.

Given all of this information, what can we do to better balance out our nutrient supplementation to prevent this from happening? One of the best strategies is going to be split nutrient, application throughout the season. This is a much more targeted approach, where we know:

    1) nutritional targets for the crop in question

    2) recent soil tests outlining nutrient composition

    3) BONUS when we consider the long-term nutrient output of supplements such as                      compost or manure

From here, we are able to formulate a plan that sees regularly scheduled nutrient introduction via fertigation into the tunnels, specifically targeted for when the plant needs those nutrients the most. In doing so, we can reduce the loss of nitrogen to the environment, prevent unnecessary buildup that impede production success, maximize the impact that each $$ of fertilizer has on crop performance, and generally contributes to resilient and long-lasting productivity of those greenhouse soils.

Interested in learning how to set yourself up for split applications during the season? Join Judson Reid and Talia Plaskett at noon (AST) on April 13th for a ‘Lunch and Learn’ session on how to set yourself up for split applications of nitrogen throughout the season! This is a great opportunity to help establish the fertigation plan for 2023 and fine-tune your calculator skills to make sure that you are getting the maximum impact for every drop of fertilizer injected into the soil. For more information, or to register for the session, please check out our learning portal.
 

Posted by: Talia Plaskett

 

 

SUMMARY of BugBites! Session 5: Shore Flies

 While shore files (Ephydridae) are primarily seen as a nuisance in protected production spaces, they can also degrade the quality of your plants. Adults are known to leave 'fly vomit' behind as they make their way through the production space. These small black specks can be found on plant parts and growing surfaces, and are no aesthetic addition to your pristine green canopies. 

The following information is a summary of session 5 of the BugBites Series: Fungus Gnats and Shorefly Suppression with Beneficial Organisms. To watch the full session, click here! 

Pest Description: 

Adult shore flies, although similar in size to a fungus gnat, are comparable to regular house flies in appearance. These insects can be identified by the 5 white spots on their wings. 

Larvae are semi-aquatic, which can be identified by their Y-shaped breathing tubes. The larvae are semi-aquatic in nature, and can range from cream-coloured to brown.  

Monitoring and Scouting: 

Traditional yellow sticky cards are effective for monitoring and catching adult shore flies. These insects are much stronger fliers compared to fungus gnats, so placement of the yellow sticky cards right at the soil line is less critical. 

Biological Control Options: 

The best method for managing shore fly populations is to manage algae build-up around the facility. The larvae, which are semi-aquatic, rely on algae as their food source. By removing a key part of their reproductive cycle, pest population sizes will be limited. The best way to manage algae is to repair any leaky points along the irrigation system, and carefully sloped surfaces to keep water from pooling. 

Next is insect management. By conducting regular scouting checks of the crop, and maintaining populations of biological control agents, you can limit the degree of pest infestation.

Dalotia coriaria; Rove beetle

• Predator to both shoreflies and fungus gnats
• Both adults and larvae are predatory
• Orange larvae are noticeable in the soil
• Adults readily move around via flight
• Ready establish in greenhouses
• Works well in hydroponic systems

Figure 2. A photo of a rove beetle in the adult (left) and larval (right) stages. stuck to a yellow sticky card.  Image taken from the BugBites! Session 5 presentation

The use of rearing boxes allows for a slow-release approach, and will help maintain beetle populations through the season. Rearing boxes can be as basic as media (ex. peat, vermiculite) set inside a Tupperware container, and supplemented with food (ex dog or fish food, artemia). It is crucial to keep this moist, but not wet. These can be placed under benches.

Steinernema feltiae; entemopathogenic nematode

• Target fungus gnats, shoreflies, thrips pupae and many others
• Forage in the top inch or two of the soil
• Water into your growing media lightly- if they get too far in, they will not be able to combat pest populations
• Not highly mobile
• 50-78F are ideal conditions
• Well suited for greenhouse environments
• Susceptible to being washed away in rockwool
• When growing in rockwool, apply after the last irrigation of the day to give them a chance to establish

Steinernema carpocapsae, entemopathogenic nematode

• Target shore flies, and thrips pupae
• Good at finding mobile pests
• No problem working in/establishing on rockwool
• Lives on soil surface (use very little water when applying to prevent from washing them too deep into the growing media)
• Ideal temp is 57-84
• well suited for greenhouse environments

* Both nematodes listed here can be applied together, since they focus on different parts of the soil.

The key for management here is prevention. By adding nematodes and rove beetles into your production routine, and managing algae growth around the facility, shore fly populations should be significantly reduced. 

Posted by: Talia Plaskett

Starting the Season on the Right Foot - Potting Mix Analysis Part 1:EC

Part 1-EC

For those of you who missed last weeks edition of 'the Root' newsletter, I've included a copy of the post below for reference. Part 2 of the potting mix mini series will dive a bit deeper into the world of pre-season assessment.

Before you start sticking your seeds in for the upcoming growing season, consider this – what exactly is IN the potting mix?! While many of us are devoted to our favourite potting mixes, changes in formulation, or lack of supply, may result in a very different product than we are used to coming out of a similar looking bag. Instead of crossing our fingers and waiting to see how the quality (and quantity) of the sowed seeds turns out, some easy testing can be conducted in order to mitigate some potential issues before they wreak having on your upcoming cash crop.  

Some of the most basic testing that can be done on a potting mix will reveal information surrounding electrical conductivity (EC), pH, and nutrient content. While nutrient deficiencies have a significant impact on seedling growth and development, today’s focus is going to be on the EC of your potting mix.  

What is EC, and why is it so important to test in potting mix? 

EC (reported as mS/cm, dS/m or mmhos/cm) measures how much electricity is conducted through a solution. In this case the solution we are referring to is a moist potting mix, and the reading indicates the concentration of ions or salts in the potting mix solution. EC will have a direct implication on a plants ability to take up water, and overall health.

Before we dig any deeper here, its worth clarifying that salts are not just sodium (Na+) and chloride (Cl-) ions, but are also essential plant nutrients:  

• Calcium (Ca2+ ) 
• Magnesium (Mg2+) 
• Potassium (K+) 
• Ammonium (NH4+)  
• Phosphate (HPO42-) 
• Sulfate (SO42-) 
• Nitrate (NO3-)

A potting mix with a high EC value has a direct effect on plant growth, especially when we are looking at germinating plants. For plants that CAN still germinate in high salt environments, and don't necessarily suffer a reduction in the number of successfully germinated seeds, there will likely be a visible impact on root and shoot development (left) compared to that of a healthy transplant (right). A delayed planting date, or weak seedlings at the time of transplant, could see a less successful transplant, later harvested product, and more susceptible crop to pest and disease pressure.