I've seen it mentioned that some people use sugar in their potting soil to prevent RKN and even use it dissolved in water to treat it. Does anyone know how much sugar you would add to a five gallon pot for prevention? I haven't seen a ratio mentioned.
Thanks
Paul

From what I read to suffocate the nematodes you can mix ½ cup of sugar into 1 gallon of water and pour directly into the soil that is affected by nematode.

I remember reading scientists use sugary water to flush RKN from the soil for research. I was under the impression the nematodes were alive after being flushed out.

Mr Robin uses sugar in the potting soil to prevent infestation? Does anyone know the ratio of sugar to soil ?

If they are potted, why would you get RKN?  Use a sterile potting mix and keep the pots off the ground I think you would be good.  

I can't see how adding sugar would prevent it, the sugar would wash out with subsequent watering.

Non of the scientific papers I've read support the use of sugar to eliminate a nematode infestation.  Most of the support on the internet for sugar therapy is just not supported.  Dr. Jerry Parsons, a retired professor of horticulture at Texas A&M, had this to say about the subject in 2006:

Yes, they are tiny buggers, aren't they?  And I would think once they are in a pot the tree is likely doomed as the roots are trapped.

I have them in NC.  From what I've read, they don't like organic mixes (though nobody seems to know why), they stay near the surface as they need light (I've read no more than a foot or so deep).  If planted in ground near a concrete slab the roots that grow under the slab may remain uninfected.  One remedy from a man in FL was to plant the tree in a bottomless 5 gallon bucket with heavy mulching - the roots grow out of the pot below where the nematodes are, and the mulch is supposed to 'repel' them.  

That said, mine are too young to know yet.  I have 3 in a raised bed with heavy organic mix about 3 ft from my house - concrete slab.  In their first year (last year) they grew like gangbusters.  I planted others out in the yard using the bottomless bucket method, they did not grow nearly as well.  There are many in my neighborhood in NC, and all the ones that do well are near 'structure' as the locals like to say.  

Thank you for all the insights into the issue!
Paul

I thought marigolds were good to suppress nematodes.

https://edis.ifas.ufl.edu/ng045

Marigold work as a trap crop for nemotodes.

RKN's natural mobility is extremely limited. This is why Dr Parson suggested a solid crop. Anything less will not be effective.