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Root-knot nematodes (Meloidogyne spp.) are minute, worm-like animals which are very common in soil. They have a wide host range, causing problems in many annual and perennial crops.

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Root-knot nematodes do not produce any specific above-ground symptoms. Affected plants have an unthrifty appearance and often show symptoms of stunting, wilting or chlorosis (yellowing). Symptoms are particularly severe when plants are infected soon after planting. More commonly, however, nematode populations do not build up until late in the season and plants grow normally until they reach maturity. They then begin to wilt and die back with flowering, fruit set and fruit development being reduced.Below ground, the symptoms caused by root-knot nematodes are quite
distinctive. Lumps or galls, ranging in size from 1 to 10 mm in diameter, develop all over the roots. In severe infestations, heavily galled roots may rot away, leaving a poor root system with a few large galls.

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Root knot nematode: life cycle

Photos - top Scarlett's turnip, bottom Donna's silverbeet

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Control in an organic garden:

Crop Rotation is the best way to avoid having this problem, although I have read that they are particularly problematic for sandy soils and in my case the first time I planted the silverbeet in the bed I got them just by leaving them to continue growing for harvest over the standard life cycle.

Certain Green Manure crops are said to be helpful in controlling it, these include nemcon mustard, marigolds and cobblers pegs.

Molasses or Sugar Drench has been widely recommended, the ratio for sugar is 1kg per square metre but I can not find the ratio for molasses at the moment... assume it also to be very high maybe as much as a litre per watering can?  -  as a foliar spray to repel chewing insects it is 2 tab per litre.

Interesting Further Reading

Brassica and related cruciferous crops can reduce nematodes when used as a soil amendment (McLeod and Da Silva, 1994).  A natural biofumigation occurs when these materials break down in the soil...

Organic amendments like dung and green alfalfa manure have been shown to increase the activity of nematode predacious fungi (Mankau, 1962)...

Stirling (1989) showed the use of poultry manure and sawdust to have benefits in controlling root-knot nematode in ginger crops...

Vawdrey and Stirling (1997) found soil drenched molasses in tomatoe pot experiments to reduce root galling and root-knot nematode population...

... in the field, sawdust and filter press (sugar cane residue) reduced root-knot nematode population... molasses reduced root galling in the field...

Root exudate of the sesame plant can inhibit nematode egg hatching, be toxic to juveniles, suppress mobility, delay adult maturation and suppress juvenile penetration into roots...

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I just cleaned out the small beans & corn bed yesterday in preparation for root crops... and found what I think are root-knot nematodes on the snake beans... I didn't take a picture as I was rushing to finish the job before sundown...

Had some marigold seeds handy so I've sown them and hopefully they germinate soon for me to dig them in before the next root planting days... I've read or heard from somewhere that molasses kills earth worms, so I was a bit reluctant to use that... someone can clarify that for me?

Here's the recipe from Annette McFarlane..

Molasses Spray
Dissolve one tablespoon of molasses into a litre of warm water.
Add one teaspoon of Sunlight dish washing liquid or other pure liquid soap (Does anyone know where I can buy this? I don't seem to see the brand 'sunlight' last when I remember to check at supermarket..)

Spray regularly over the leaves of all plants attacked by caterpillars and other chewing pests. Caterpillars would rather starve than eat leaves sprayed with this mixture. It has also been used with success by some gardeners as a possum repellent and for the treatment of soil affected by root knot nematodes by doubling the concentration of molasses.
The above recipe is for chewing inspects like grasshoppers and is sprayed on the leaves. I doubt that this small amount sprayed on THE LEAVES (to make them taste yukky) would affect the earth worms.

Not sure about sunlight but you might find something in the laundry aisle that is pure soap - lux flakes is but not sure if you can buy it as a liquid?

To make a molasses drench you use a lot more and pour it using a watering can directly into the soil - this will kill other soft bodies insects like earth worms and maybe/ probably other good soil bugs.... but it will also kill nematodes and you can introduce good bugs (including worms) by incorporating compost and a few shovels of dirt from a non infected garden a few weeks later.
The recipe says "for the treatment of soil affected by root knot nematodes by doubling the concentration of molasses.".. I assume this is for drenching?
Okay, so I didn't read it properly .... sorry was in a hurry :) Okay, that isn't anywhere near as much as I thought... the sugar recipe I found in a book by Tom Wyatt was for 1kg per square metre which is why I thought you would have to use a lot more molasses than that!
i reckon you could probably substitute 'earth choice' or similar dishwashing liquid because it's biodegradable and no phosphate

or you can dissolve lux flakes in hot water first (always a bit messy especially if you're going to use a sprayer - easy to clog it)
I use earth choice's laundry liquid, they are nice :) I went and bought their dishwashing liquid as well after your suggestion.. will give it a try on the weekend .. probably on the tomato bed which I just transplanted.. ^^ I think I might have nematodes on many beds...... I thought they like sandy soils..
There's also an article on Nematodes in the home garden

It mention French marigold which were mentioned in other sources I've came across before. Now, I've got marigold in the garden which I can harvest seeds from, but I have no idea what type of marigold that is... I've googled images both French marigold and african marigold but really could not tell the difference.. does anyone know how to tell French marigold from others?
*Groan* guess what type I planted last weekend?


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