What are Nematodes?

What are Nematodes?

Nematodes header image with Quickcrop logo

If you are new to vegetable gardening you will probably be imagining yourself carefully nurturing your healthy, glossy plants, perhaps giving them a little water from your pretty yellow watering can. You see yourself smiling with satisfaction as each crop bursts from the soil, only to mature into a perfect example of the best mother nature has to offer. That's how I felt when I started anyway - and while I have had brief peeks into that beautiful world, the day to day reality requires a little more effort.

The main problem I have is that there's an infinite amount of other creatures who seem to feel they are entitled to my gardens bounty, without putting in any of the work. While I can't say I feel too friendly towards the culprits, I don't want to start dousing their habitats with pesticides to keep them out - so I need to find some alternatives.

What are Nematodes?
Nematodes are microscopic roundworms which are naturally found in your garden soil. There are vast numbers of different species (the total number is estimated at about 1,000,000), but we need only concern ourselves with the ones that are going to help us out. These are known as 'insect parasitic nematodes', for reasons that should become clear below.

These tiny worms prey on the larval stage of certain pests, thus breaking the life cycle and serving as a very effective natural control. Different nematodes target different species, so you first need to identify your problem and get the right nematode for the job. 

Grubs

'Supernemos' for example will control Vine weevils, Scarid fly, Strawberry root weevil, Chafer grubs, Leatherjackets, Wire worms, Cutworms, Cabbage worm, Fungus gnat larvae.

Why Use Nematodes?
Nematodes are more typically used in situations where crops are being grown at scale (e.g. in nurseries or large commercial polytunnels); however they can also be used by the home grower to help with particularly problematic infestations or persistent plant or lawn damage.

In comparison to using chemical pesticides or substances, nematodes have a number of benefits. They don't leave any chemical residues behind, they are safe to use around children and pets, and they won't harm your plants. Remember, these microsopic organisms are already resident in the soil.

Jumping for joy

Parasitic nematodes, generally speaking, work in a very targeted manner. This means they won't harm beneficial insects like bees or ladybirds. However they can affect some non-targeted insects in some cases, which is why it's important to only use them if a) all else has failed, so to speak and b) when you have some definite evidence that your target insect is the one causing the problems.

Nematodes are fast acting and produce visible results when used correctly.

How Do Nematodes Work?
As we've already said, the nematodes contained in most retail brands occur in nature and will more than likely be present in your garden anyway. All we are doing here is increasing the numbers to tip the balance in our favour.

After applying the nematodes, they will seek out the larval or grub stage of their targeted pest and go in for the kill (Note: stop reading now if you're squeamish!). These tiny crusaders then enter the body of the host and start to tuck in.

Grubs

The nematode secretes a bacteria which kills the host (usually in the space of a couple of days), and then settles in for a bit of reproduction. The dead larva essentially becomes a nursery for juvenile nematodes, which then head off in search of new grubs to infect once they've eaten the first one. 

How are Nematodes Applied?
Depending on the use case, nematodes can be 'put to work' through foliar application (applying directly to plant leaves) or by soil application. This is commonly done by mixing a solution with water, and then using a watering can, sprayer or irrigation system to treat problem areas.

As a general rule soil should be moist, and careful attention should be paid to soil temperature. Some nematodes can work at cooler temperatures, while others require a certain level of warmth to be effective. It's also important to avoid applying in strong or direct sunlight, as nematodes can be sensitive to UV light. Aim for late afternoon or early morning applications.

Detailed instructions should be included with the pack. Nematodes also need to be kept refrigerated to remain viable. They will also have a printed expiry date, and should be used before then.

Entonem Nematodes
This product contains the nematode species Steinernema feltiae. It can be used to control numerous larvae or 'pests', including but not limited to Vine weevil, fungus gnats, tomato leaf miner and cutworms. Unlike a lot of other nematode options, the treatment has been shown to be effective at lower temperatures (above 8° C), although higher temperatures are preferable.

Entonem applications can control the larval stage of various 'pests': the nematodes will enter their body cavity and release symbiotic bacteria, killing the grubs. You should see the larvae turn brown 7-10 days post application.

Vine weevil

Adult vine weevils can do a lot of damage, and can often be a problem for plants in containers. The adults are 8-10mm long and dull black in appearance, with yellowish speckles on their back. The larvae tend to be at their most active from autumn to spring, but they can be found all year round.

Capsanem Nematodes
Featuring the species Steinernema carpocapsae, Capsanem can be used for targeted biological control of leatherjackets - the small greyish-brown grubs which are the larvae of crane flies (aka daddy longlegs).

Although these larvae contribute to our ecosystem by feeding on decomposing organic matter, a few species are unfortunately known for feeding on plant stems and roots. They can also cause bare or discoloured patches in lawns.

If birds are in the habit of pecking at your lawn, this can often be a tell tale sign of a leatherjacket problem, as can plant stem damage at soil level. Leatherjackets look like small worms, although it is rare to spot them above ground.

Leatherjacket larvae tend to be most active between August and October, so this is the ideal time to apply Capsanem nematodes.

Steinernema carpocapsae can also be used to target:

  • cutworms
  • silver-y moth
  • tomato leaf miner
  • shore flies
  • sycamore lace bug
  • as a foliar spray to target Cabbage White butterfly and Box Tree moth caterpillars.