I'm growing some figs in-ground in an old garden that has had a steady flow of nursery-bought tomatoes/peppers/potatoes/etc transplanted into it for about 40 straight years.  I assumed it would be full of root knot nematodes, and it is.  The trees are about 19 months old and were nematode-free when they were planted bare-root in the ground about 9 months ago.

The trees have grown well so far, but I want to air-layer the tops off and pot them up.  I've got some questions about how to do this given the RKN problem:

1) How high above the soil should the air-layers be?  (Aside from concerns about splashing of soil, will RKN climb up the trunk?)

2) There is dirt/dust all over these trees, especially the lower 12-18", so how do I ensure that there aren't any RKN on the trees?  Scrub them with soapy water?  Spray with bleach or neem oil or sevin?  Rub them down with salty water?

3) I made a couple hundred cuttings and am rooting them in black trash bags (hopefully they'll root).  My plan is to root them, plant them around the property in the spring, then check them in the fall for RKN.  My thinking is that this would be a way to map out which areas do and do not have RKN, so I'd know where I could safely plant some hardy varieties in-ground.  Is this a decent method, or is there an easier way?  Also, related to question #2, how can I ensure that these cuttings are free of RKN so I don't infect the yard when I plant them out in the spring?

Thanks for reading, any insight or advice would be much appreciated :)

I don't think you have to worry about RKN above the soil line, 6" up or more you would be fine.  They feed on roots so as long as you are free of the soil you will be ok, a spray of bleach water would not hurt but is not needed.  You can get rid of them in an area by keeping it fallow for a season.....in this case fallow means no vegetation at all, no weeds nothing they will starve out to a large degree.  As they largely subsist on certain weeds keeping the area weed free is a good idea. The RKN like hot dry soil so mulch it HEAVY to keep it cooler and moist.  RKN are mostly in the top 12-18" of soil.  A common trick is to bury a bottomless 5 gallon bucket up to an 1" of the rim.  Plant the fig in it and it forces the figs roots to go deep before spreading out.  It makes the feeder roots which are the ones the RKN want to be way underground where they are safer from the nematodes.    

Thanks WillsC!  Lots of good thoughts in that post.

Well here in sandy hot Florida the RKN are a pain but I have found that the mulch is your best friend.  I go through a LOT of it....6' diameter circle per fig 10" thick per year but keeps my plants healthy and RKN symptom free. 

It's impressive that the mulch is that effective for you.  I had assumed it would only be a slight benefit (maybe reducing the problem by 20% or so), but you're having much better results than that.  Makes me feel more hopeful about my odds of success, thanks for adjusting my thinking.

The main thing to keep in mind is that nematodes are essentially hair sized worms. They will primarily spread on infested soil (which can be on your shoes, tools, etc). Air layering should be no problem as long as it's kept clean!

Google neem cake. It is supposed to kill nematodes, and fungus and is reportedly good for spraying to supress insect pests on plants good for fertilizing crops.

Greenfin,

On my sand with my RKN it is about 100% effective....the problem is there are a bunch of types of RKN and some are tougher than others.  

I never even heard of RKN before reading about it in this forum. It sounds pretty crappy. I don't believe in "weeds", so I let everything grow unless it is harmful in some way. One of my main "weed" crops is wild mustard. As I understand it, mustard deters nematodes. It might not be a magic bullet, but I think if I had an RKN problem, I would plant some mustard. Plus, mustard adds nitrogen to the soil and I think it looks pretty (for a weed).