How to get rid of root knot nematodes from your veggie patch

Root knot nematodes or eel worms are those hidden annoyances that you don’t really know that you’ve got them until it’s too late. Root knot nematodes are a microscopic parasite that sucks the life out of your plants. If a plant collapses for no reason (looks like it needs watering but doesn’t), looks droopy but bounces back in the evening, is generally failing to thrive and you get these little nodules on the roots it’s probably likely you have an infestation of them. Be aware that some nitrogen fixing nodules on beans and peas look very similar.

Recently I noticed some swiss chard struggling to take off. I thought perhaps I wasn’t watering enough or I had planted too close. I decided to relocate a couple and that’s when I found the problem.

Swiss chard with an epic root knot nematode infestation

What plants are affected by root knot nematode

Most common plants we see affected by these guys:

  • Tomatoes
  • Swiss Chard
  • Beetroot
  • Carrots
  • Cucumbers
  • Zucchini
  • Capsicums
  • Squash
  • Pumpkins
  • Tromboncino

Often with root crops you won’t notice them until harvest time, where you get these ugly bumpy looking root veggies.

Bumpy carrots with root knot nematode infestation

How to get rid of root knot nematodes

Getting rid of these are tricky, but you can get them under control with a bit of patience.

Firstly dispose of any affected plants by binning them or burning them. They will die in a hot compost, but you need to make sure you’re getting up to that 60 degree celsius mark (which is tricky). You don’t want them in your cold compost bin or worm farm, as that’s just going to spread them even further.

Some common strategies include:

Bio fumigate Green Manure

You can purchase special green manure crops that are said to eradicate them. These generally include a mix of brassicas (mustard in particular). Generally these are things they don’t like when they start to decompose (a substance known as ‘isothiocyanate’).

With this kind of green manure crop it’s important to dig it in not just chop and drop, which unfortunately is going to disturb a whole lot in your soil so keep this in mind as essentially you’re going to have to build up the soil again.

Go fallow and turn it over

Take out everything and leave it empty for a few seasons. Similar to the green manure crop this is going to get rid of a lot more than just nematodes. Essentially you are starving them out and ruining your soil at the same time, but if they are really bad it might be a last resort. Extreme measures you can also solarise your soil by putting black plastic over it.

What we do:

Plant things they don’t love

Instead of wasting space with green manure or time with fallow ground, we opt to plant things they don’t take an interest in.

Brassicas (broccoli, cauliflower, kale, cabbage, kohlrabi, turnips, bok choi, radish etc), Mustards, Corn, french marigolds and Leeks are our go to crops. They also hate asparagus if you have them pop up in a perennial bed.

Add beneficial microbes and Mycorrhizae

Having too many of one thing, in this case a root knot nematode infestation, means the good guys in your soil are out of whack. We add Mycogold to our beds that have issues and water it in with worm casting tea and sea weed solution. We continue to do this until things kick back into gear. Making sure your soil is healthy in the long run is going to help.

How to avoid root knot nematodes

Like anything, a healthy garden is going to have a wide variety of annoying bugs every now and them. So it’s likely you won’t see the end of them, so it’s all about management.

Feed your soil

Ensure you’re adding well aged manure, loads of compost and worm castings (compost gold!) to give your soil a boost. We’re taking so much out of it by growing the food we eat we need to make sure it’s healthy and restored.

Rotate your crops

Where possible, move your crops around. As we plant so intensively in a small space we need to do this particularly for the more pest susceptible plants.

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Have you had an infestation of root knot nematode? What remedies have you used? Leave a comment blow.

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