Organic Cutworm control in the garden

Cutworms are the bane of a gardeners life, when planting out seedlings cutworms can make short work of all of your diligent growing out.

There are a number of different ways to protect your plants against cutworms and the most commonly recommended solution is to plant the seedling into a collar (or grow them in a collar) these collars can be cardboard tubes like toilet rolls or even PVC tubes.

This is a great idea, especially if you only have a few seedlings to plant out. However here on Livingseeds Farm we plant out thousands of seedlings and that adds up to a lot of toilet rolls.

I have heard and read about using soil calcium to combat cutworms, and that soils that have a proper calcium availability will have a lower or no cutworm incidence. I’m not sure if it’s soil pH or if it’s the actual calcium availability? However, looking at what we have experienced over the last two years I think its the physical calcium that makes the difference.

So, all very good and wonderful, how do we go about proving it. This is all anecdotal and it’s pretty hard to prove conclusively, however read along and see what we have found.

Typically here on Livingseeds Farm, we never had any specific cutworm program besides going into the tunnels early in the morning and manually catching the cutworms either in the act or just post act. Cutworms typically do their dirty work early in the morning and catching them is simple. As long as it’s done within an hour to two of the decapitation, they can be found by scratching around the severed seedling and collecting all the cutworms. They are typically found in a 2-6 cm zone around the seedling and about 1 or 2 cm deep. These were then fed with glee and much appreciation to our laying hens, who turned them into lovely eggs for us.

Tunnel with about 300 heirllom tomato plants. Sheaves of wheat are drying waiting to be threshed.
Tunnel with about 300 heirloom tomato plants. Sheaves of wheat are drying waiting to be threshed.

We would lose about 10-15% of our seedlings every year and basically accepted the fact that this was part of the deal when growing organically and not wanting to use pesticides.

I had been speaking to a few people about the Calcium – Cutworm theory, and 90% of the people shot the idea down as a waste of time. Always up for a challenge and proving people wrong I though we would give it a bash.

Knowing that all calcium is not created equal I decided to do a few simple tests. The kind that are easy and simple to replicate in the garden or in our case, in the fields.

Just a quick look at the different Calcium’s available to the gardener. (No need to go into cations anions and CEC (Cation Exchange Capacity) of soil and how things are locked up and released. Suffice to say it’s interesting and very important, but not right now.)

Dolomitic Calcium is the cheapest, has the lowest availability, and takes years and years ….. and years to become available. Has a high Magnesium ratio that when it’s release, unfortunately also locks up other elements and tends to harden up your soil.

Calcitic Lime also known as Landbou Kalk, comes in various “kinds or sources and grades” and is the most commonly available. This is what is mostly sold as gardening lime. Nothing wrong with it and it works. (Again depending on the source / quality)

Bone Meal a superb source of highly available calcium and is held beautifully in the soil, it’s readily absorbed and is a much preferred source of calcium.

Gypsum. The most highly available source of calcium, also has a good ration of sulphur. If you are low in calcium this is a great way to fix a shortage very quickly as the plants can use it almost immediately. The Sulpher (anion) is locked onto the calcium (cation) making it freely available for absorption.

OK, onto our cutworm story. Last year we started our trials in two of our tunnels and found the following. (Both tunnels were planted to tomatoes)

All of the other tunnels were treated as normal and we harvested cutworms every morning for our hens.

In one tunnel we added in Calcitic Lime (Landbou Kalk) at around 150-200 gr per running meter and planted into the soil. Our cutworm activity was not noticeably reduced, and we had to control by hand.

In the second tunnel we used the Talborne Organics Vita Bone Phos at a similar rate. There was less cutworm activity, but we still had losses in the tunnel. There was a clear drop in cutworm activity and I felt it was well worth pursuing the reasoning that calcium reduces cutworm activity.

I decided that this year I would do a bit more to test this theory out. We ran the following calcium regimen in all of our tunnels and any open beds where we transplanted seedlings.

First the Vita Bone Phos was added to the soil (at approximately 150- 200 gr per running meter) and lightly worked into the top 5 cm of soil. The seedlings were planted directly into the soil along a drip line and then a tablespoon of the BonePhos around the seedling.

5 week old tomato seedling with NGP Soil Build around the base.
5 week old tomato seedling with BonePhos around the base.

The tunnel where we had the Vita Bone Phos in last year had no seedling losses at all. We have to date lost only 6 seedlings this year, we have planted out thousands, both in tunnels and in open ground.

So do I believe that calcium stops cutworms, oh yes 100%. It just needs to be the right calcium.

Our seedling loss as a percentage this year (based on calcium treated soil) is less than 0.25% !! Going from a 10% loss every year to .25% is a huge drop.

The only place that we did not do the calcium treatment was on the Corn and Bean plantings. It’s noteworthy to see that we lost 15-20 % of our bean and corn plantings. What we also did not do, was the cutworm follow-up every morning in the bean and corn fields, so the damage was higher as we were not concentrating our efforts there. We were more concerned at what was happening (or not happening) with the calcium treated seedlings. Patting ourselves on the back and revelling in getting a grip on the cutworms by using the soil against them. By the time we woke up, the damage was already noticeable in the untreated areas.

Talborne organic Vita Veg and Vita Bone Phos
Talborne organic Vita Veg and Vita Bone Phos

 

My recipe now for cutworms, not just scratch them out manually. Add in 150 – 200 gr of Vita Bone Phos per running meter, and sprinkle just one tablespoon of BonePhos around each seedling. It’s simple, 100% organic, improves your soil quality and most importantly, IT WORKS!

 

13 thoughts on “Organic Cutworm control in the garden

    • SelfSus says:

      Yes, we just work it out on an average. The container (medium sized cup) that we use holds 150g of BonePhos, so we use that to gauge the approximate dosage.
      It’s never exact, more of an approximation.

  1. Magdil says:

    Thanks, Sean! really appreciate and will def try it as we have quite a huge problem with cutwoorn in Oudts and I did not know how to get rid of them!

  2. Cynthia says:

    Thank you, thank you, thank you, my favourite plant was recently destroyed by cut worms and they are manifesting all over my garden. I have literally tried everything but to no avail – once again my heartfelt thanks – tomorrow I will follow your recipe. Watch out cut worms !!

  3. SelfSus says:

    Hi Helen, I have no idea about egg shells working against cutworms. However they can only help.

    One would need a LOT of egg shells to make a meaningful impact.

  4. Julia Farmer says:

    Thank-you so much for all the time and effort you put into this research. I have resorted to using cut toilet rolls to protect my pepper and tomato seedlings but seeing I grow a lot of lettuce it would be very time consuming each one of them! I add agricultural lime (not sure what type of lime that is) and bonemeal to all beds prior to planting and I also hunt for cutworms and then feed them to our chickens – it is great to read that I am mostly following the same organic practices as you. I will definitely get some Vita Phone Phos next time I am in SA as we don’t have that product in Botswana yet.
    Thanks again!

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