Question about Nematodes

[bkay2000]

Do you guys in the cold North Country have root knot nematodes? From what I've read, freezing temps kill them (how long and how cold, I'm not sure).

bkay

[Tigger]

The north certainly has the classic foliar nematodes (Fragraria sp.). They don't present with symptoms until the weather gets hot and humid, so those Minnesota folks who think they have them are fooling themselves. Freezing temps don't bother the eggs.

[Chris_W]

Yes, root knot nematodes are up north too, but not usually much of an issue. On the rare occasion I've seen it on a perennial there hasn't seemed to be any indication above ground that there was a problem. We got in a batch of bare root Astilbe this spring that were loaded with them. I pitched the entire batch and the company refused to give me credit as I didn't get confirmation from a laboratory, but that would have cost as much as the plants so I didn't pursue it. The thing about it is that the crowns themselves looked fine and probably would have grown okay.

I'm not certain that your problem was entirely due to the root knot. Like Bill mentioned there was a lot of rot on those roots you pictured, too, and that rot, for whatever reason, may have had more to do with the decline of the plants than the root knot nematodes. The root knot may have prevented the plants from recovering better from the rot.

Not sure if that helps you at all, but yes, they are present in northern gardens too.

[bkay2000]

So the idea that freezing the pots would kill the nematodes is not a viable idea?

bk

[Pieter]

So the idea that freezing the pots would kill the nematodes is not a viable idea?
bk

I wouldn't say so. I received some plants from a gal in Quebec a few years ago where some were obviously nematode infested and Quebec gets one heckuvalot colder than we do here in Canada's banana belt. Frost certainly didn't kill them for her, I ended up taking care of the nematode infection with a bleach bath and continue to enjoy the lovely 'Ray of Hope' that I rescued with the procedure.

[redcrx]

Would you describe the bleach bath please.

[Bill Meyer]

Hi Bkay and All,

There is getting to be some confusion between foliar nematodes and root knot nematodes. To answer Bkay's question, there are a lot of species of root knot nematodes (Meloidogyne), most of which are tropical, but there are two species (hapla and chitwoodii) that are found far into northern regions. If the people who identified yours said they were a tropical species then freezing them might kill them off. If they are one of the more cold-resistant species then it won't. Foliar nematodes, BTW, can survive temps lower than -100F.

There is also a lot of confusion in these posts about topical treatments, drenches, dips, sprays, etc., with products that have no ability whatsoever to get into a plant and kill the ones inside it. Unless a product is systemic or translaminar (soaks through), it will not do anything to nematodes inside the plant. There is no point in torturing the plant further by burning it with bleach or clove oil or other caustic chemicals. It won't do anything to the ones inside the leaves or roots.

With foliar nematodes, by the time you see symptoms there may well be tens of thousands inside the plant. Even if you could kill every single one outside the plant, as soon as you are done more will come out of the plant and get everywhere again. The inside of leaves is where they breed and when there gets to be too many in there they come out and get washed around by rain or watering. Root knot nematodes aren't quite so numerous inside roots, but they breed in the galls they cause.

This new snake oil product called Nemakill is mostly clove and cinnamon oil. People should be aware that there are broadleaf weed killers on the market that are made up of clove and cinnamon oil. Clove oil is used to kill plants, and because it is not systemic it only kills the tops and not the roots. It is also considered a possible carcinogen, although there doesn't seem to be much evidence of that that I could find. There are no studies that show it kills nematodes inside a plant, likely because there is no way it can do that, although I suppose it is possible that when it kills the leaves it may kill the nematodes inside them too. That may explain how the AHS tests showed it killed them in cut off leaves in petri dishes.

..........Bill Meyer

[Pieter]

Bill is absolutely correct, we're talking at crossed purposes here. I was talking about my experience dealing with foliar nematodes.

[bkay2000]

I checked with the nematode lab at University of Missouri. They don't think freezing will work.

I just emailed Dr. Grewal to see if he has any ideas.

The further I go, the more it looks like I may have to toss everything.

Bummer.

bk

[bkay2000]

How about heat treating like you would foliar nems? ( I have big sinks in my workshop.)

(The 10% bleach solution didn't make much, if any, difference. I tried that when I thought it was rot.)

bk