Nematode treatment

[desicody]

I have nematodes in isolated areas and would like to try a hydrogen peroxide treatment. Using 3% hydrogen peroxide, what ratio H2O2: water do I use? Do I spray this on both the leaves and on the soil? How often do I do the treatment and how effective is it?

[ViolaAnn]

I believe the recommended ratio is half cup H2O2 to 1 gallon of water and spray the plant well and likely the area around it. Don't know how well it works, but some of mine that were infected are looking better this year. Another, however, is not. I believe they are also doing tests with spraying heavily with an ammonia solution.

The big problem, of course, is that by the time you see the evidence of them in one plant, that have multiplied and also moved on to others.

What I've been doing the last few years is an extremely thorough cleanup in the fall, cutting everything back and spraying everything with both ammonia and H2O2 solutions.

The jury is still out on how well it works.

[Chris_W]

Actually, based on the ratio when using Zerotol which is a stabilized and concentrated hydrogen peroxide, you would mix no water in a 3% solution. Zerotol is typically diluted down to about a 3% solution from the concentrate it comes in (if my memory serves right, I don't have the label in front of me right now but will try and check later).

That means it would take a TON of 3% hydrogen peroxide to do anything, and even then the results probably won't be all that great. While it might suppress some of the nematode symptoms it won't get into the plant enough to kill them and you would need to spray on a regular basis - monthly? weekly? probably not enough data out there to tell.

To treat bare soil the best way is to heat treat it using boiling water poured over the entire area, overlapping all the soil as you go so it gets really hot several inches down. BE VERY CAREFUL NOT TO BURN YOURSELF. Heat treating the soil is something like 98% effective at getting rid of nematodes in the dirt but if they are in the plants then you would need to lift the plants, heat treat those, heat treat the soil, and then replant later on. This can set the plants back quite a bit, sometimes even kill them, and if not treated hot enough or long enough the nematodes could come back too.

Years ago there was an article in the hosta journal about a guy who pours boiling water right on top of his plants and on the the surrounded soil to get rid of nematodes. The talk in the society after the article was published was that his hostas had more to fear from the damage from his pot of boiling water than the nematodes themselves but I think you sometimes just need to pick your own battles. To me I'd rather have tiny nematode free plants or start with new plants in treated soil than have huge clumps with worm infested foliage.

Hope that helps a little, and good luck with whatever you try.

Chris

[Tigger]

The AHS is finding research at the University of Tennessee to see if there is an effective treatment available to both (we hope) commercial and home growers. That is, something easier (ideally a crown drench, applied at the right times) than the very hot water bath treatment that Chris describes elsewhere. There should be a report after this growing/research season; AHS members will get a summary in email, I expect. I'm on the scientific advisory committee for the project.

David

[Phil_and_Gayle]

As mentioned above, once you see them they are likely on their way to surrounding plants also. In the last issue of the Hosta Journal I contributed my treatment method(s) for nematodes (pg73, Volume 45-Number 1). Rick Goodenough and Harold McDonnell also contributed to that Q&A article. If you don't have access to the Hosta Journal send me your email address and I can send you the details for my small portion.
In summary, heat treating is a pretty drastic measure. My success rate with heat treating so far is 50%; half are alive, healthy and nematode free, the other half are dead. Less drastic is using chemicals. I use a granular insecticide that contains Imidacloprid. It's not as effective as heat treating, but at least it has never killed a plant!

[ViolaAnn]

But is's also totally not available in many places such as Ontario.

[Noreaster]

but I think you sometimes just need to pick your own battles. To me I'd rather have tiny nematode free plants or start with new plants in treated soil than have huge clumps with worm infested foliage.



Chris

A couple years, after I became aware that some of my hostas had nematodes, I dug about five of them up and did the heat treatment thing, and poured the boiling water on the soil. The next year I had smaller, but clean plants. Or so I thought. The following season all the heat treated ones looked infected again.

It was a ton of work that in the end failed to correct the problem. Seems like every year I see nemes in a new hosta, even though that one looked clear last year and wasn't even in proximity of any of the known infected ones.

I choose to just live with them. I feel they are inevitable....and life is too short to dig up and boil everything is site, worry about the rain, worry about all the likely infected companion plantings- has anyone ever seen Brunnera NOT infected with nematodes? Yeah, I'd rather not have some streaky brown spots in August, but it is what it is, for me.

[Noreaster]

I use a granular insecticide that contains Imidacloprid. It's not as effective as heat treating, but at least it has never killed a plant!

No, but many believe Imidicloprid is what's killing all the bees!

[ViolaAnn]

Noreaster wrote, "has anyone ever seen Brunnera NOT infected with nematodes? "

Therein lies a large part of the problem. Nematodes are not just a hosta problem, but they affect a wide variety of perennials and as long as we grow those plants, and purchase from local plant sales, we are going to have nematodes. I'm also seeing them in more hostas each year and they are starting to show now.

[Noreaster]

I am quite sure I have them in ferns, and I think Heuchera too. From everything I've read, there are no chemical controls available to the home gardener. Digging up, boiling soil, throwing out...and still not being able to guarantee elimination,just holds no appeal. All I wish for is that some hosta loving scientist to one day come up with a magic bullet for these things. It seems strange that we have ways to eliminate worms in pets, but not plants.

[Bill Meyer]

Hi Everybody,

At this time of year more than 90% of the nematodes are inside the leaves of the plants (not just hostas) and can only be killed by heat or chemicals that can get into the leaves. Hydrogen peroxide, along with bleach, ammonia, and insecticidal soap are all just topical treatments. They can only kill nematodes on the outside of the plant or in the soil. They are contact-kill products only. It is a waste of time to try killing the small number they can reach at this time of year while the great majority hide safely inside the leaves.

Topical treatments can be effective at reducing the numbers in the spring when the nematodes are still climbing the outside of the petioles to reach the leaves. All the above topicals have virtually no residual action save for insecticidal soap which will last a few days, so you would have to use them at least once daily to keep the nematodes out of the plant for however long they are entering it, which may be several weeks.

The only useful bit of information to date out of that study going on now is that imidicloprid doesn't work on nematodes. It was tested in the test wells on nematodes in water and didn't work. This is unsurprising because in previous contacts with Bayer their people said it doesn't work on nematodes. There have been no studies that show it has a part in bee colony collapse - only that it is present in minute amounts which are not harmful in hives. It may make the bees move their colony because they don't like it. It will kill individual bees if used on plants in flower.

While there are chemicals that can rid gardens and nurseries of nematodes, the EPA still refuses to allow anyone to use them on ornamental plants or on residential properties. No new products have been or are being developed that show any sign of being anywhere near as effective as the restricted ones. There is no hope of "magic bullet" products in the foreseeable future, so we pretty much have to learn to live with them. Treating with topicals for the first month will help keep the numbers down, but they won't go away.

That study referenced above is looking at topical treatments with the exception of imidicloprid, Cygon, and Pylon. Neither imidicloprid or Cygon was effective and Pylon, while effective (but seriously expensive) is restricted to greenhouse use only because of bird kills.

While topicals can reduce numbers effectively if used at the right time and used very frequently, they do not offer any hope of ridding a garden or nursery of nematodes. Sterilization is the only way to do that, either with heat or chemicals. Hopefully nurseries will not try to reduce numbers enough that symptoms don't show so they can sell infected plants. Just a few living nematodes in a plant can turn into tens of thousands in a garden very quickly. They are very good at what they do.

.......Bill Meyer

[ViolaAnn]

"so we pretty much have to learn to live with them" that's the conclusion I've reached. Though I refuse to share or sell any hostas from garden without a real warning that I've had nematodes and I also refuse to buy from plant sales.

I DO continue to do a really good fall clean-up and cut down and dispose of my plants - not in the compost and I soak the base of the plant with both ammonia and H2O2. The also get a bath of ammonia mixture when they are emerging. I have seen a reduction of nematodes in a few plants which had them, but not in others.

BTW, do nematodes affect daylilies? If so, what do they look like?

[Bill Meyer]

Hi Ann,

I haven't heard anywhere that they get into daylilies, but they do get into a lot of other plants and even some lawn grasses and weeds. The last list I saw was several years old and had over 700 species on it. It included heucheras, brunneras, rudbeckias, echinaceas, various ferns, and many other popular perennials. From what I've seen, some of those are much more likely to be infected in nurseries than hostas are.

....Bill Meyer

[ViolaAnn]

Basically it means that our chances of avoiding nematodes are just about nil!