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RE: Nematode killer selection

  • Subject: RE: Nematode killer selection
  • From: "Andrew Lietzow" alietzow@myfamily.com
  • Date: 30 Sep 2003 11:20:09 -0600

Dear HMinnesota / Tom Carlson, 

I'll take a stab at answering these because many are busy battening down the hatches, getting ready for winter.  Please note that if you are commercial grower, your treatment regimen and response would be totally different than if you're a casual gardener.  Of course, you already knew that... 

1)  If you had one chemical to pick to kill every nematode in your garden by drenching, which would you pick?
Nemacur 3, Zero Tol, Diazinon 4E -- in liquid form, if available (to make drenching easier) and in that order.   Some are restricted use chemicals, and not readily available in IA.  I presume the same problems, or worse, for MN.  Zero Tol appears to be readily available, is comparable in performance with Diazinon 4E, doesn't require an applicators license, and thus it seems like the obvious choice.  

RE>>Nemacur & Vydate & Cygon - Ref. article "Control of Foliar Nematodes on Hosta", The Hosta Journal, Vol 30, No 1 (Spring 1999), pgs. 78-83.  Unfortunately, Nemacur 3 is not available in Iowa (only Nemacur 15g and I'm not so sure of that any more).  Zerotol should be readily available.  Vydate and Nemacur are restricted use chemicals (don't know about Cygon) so there are hurdles you have to jump through to obtain these chemicals.  

RE:>>Terrachlor & Peroxide & Pylon - I am not familiar with these.  Ask your nursery supply places for their experience.   Hydrogen DI-oxide is the active ingredient in Zero Tol, and I believe others have stated that Peroxide is ineffective.  

RE:>>Zero Tol 2% solution - Both Parwinder Grewal and Bob Solberg have been quoted as proponents of Zero Tol.  I have no experience with this chemical but it seems to me that if one CAN purchase this product WITHOUT obtaining a chemical applicators license, this would be the effective treatment of choice.   

2) >> If you select something that sterilizes the soil, will it ever come back? 
Sterilizes the soil?  You mean like with boiling water?  Well, if you get the soil so hot that it becomes "sterile" certainly all plants will die.  For chemicals, I suppose if the concentrations are outside the recommendation dosage, living organisms will also die.  I'm not sure what you're asking here. 

>>Will it kill trees?
If you read and follow label directions, trees and plants should not be adversely affected.  The mechanism for control attacks animals, not plants.  

3)  If the nematodes live in the plant and you cut off the leaves at the ground and drench the roots and surrounding soil with one of the above solutions, will the solution be absorbed into the remaining roots of the plant and kill the nematodes?
Have no experience on this one.  Foliar drenches of Nemacur 3 have caused necrosis on exposed tissue (ibid.), especially when applied in the hot sun, so it's probably wise to apply such products during a dormant period, or with cut back leaves as you mention.   A thorough application is of course better than a hap-hazard one so reading label instructions will serve you well. Most IPM protocols state that the goal is not 100% eradication but effective control.  With nematicides, it's probably more cost effective, and beneficial to the environment, to achieve 80-90% control than 100%.  

As an aside, for our garden guests to expect 100% flawless leaves, aren't we better off recommending that in their gardens they plant silk or plastic versions of Hosta?  :-) While I LOVE a flawless Hosta as much as anyone, if I set my expectations that high, most of the time I'm going to be very disappointed with my garden.  I think we do some disservice to the potential buying public when we set our standards, and their expectations, so high.   Here in the Midwest, we have hail storms that are a bigger problem than nematodes, so I just refuse to get too excited about these pests.  

Why are we "freaking out" about nematodes?   I've seen people reject plants that had burn holes from water droplets on their leaves, and they act like the plant will be cursed forever instead of just one season.   Are nematodes a "quarantined" pest?   Anyone know?  Of course, when you're running a nursery you've got to jump through a lot of hoops which disappear if the burden is placed on the home gardener.    

4)  I don't know how many of the above chemicals are available in Minnesota?
I would imagine most of them.  Call your local chem and nursery supply houses.  They love to sell chemicals and cure pest infestations in the process.    

5)  If you leave a plant in a 2% Zero Tol solution, will it kill the nematodes and not the hosta?
Find Parwinder Grewal's article in THJ, Vol 32, No. 1, pgs 64-66--this is a very down to earth article written in easy to understand terms.   My question to you, however, is, "Why would you want to leave a plant in the solution"?   Even water will eventually kill the Hosta long before the nematodes are gone.  I'm sure I'm missing something here.  

>>I agree with previous posters.  I think hosta lovers could benefit by someone 
creating a database of hostas that get nematodes and those that don't.  I 
think there are some plants that don't get them or at least show the symptoms.

Now you're talking about something that is of serious interest to me.  Unfortunately, there is a difference between having a serious interest in something and having a "passion" for it. :-)  Someone more passionate than I will have to add these fields into their database.   Maybe Mike Lemke or Lu Treadway will respond to this, or even our AHS Registrar?  

Personally, I think Ploidy analysis is much more quantifiable, useful, and easily implemented.  Though a subjective listing or resistance experience of cultivars against viruses and nematodes might be doable, the problem I see is that one year a plant will show serious damage and the next year may be unaffected.  Is this due solely to microclimate issues or is there a genetic response for resistance being triggered?  How does one quantify a plant's resistance to disease?  At least with morphology, we have established standards.  

For resistance to pests, it seems that the scale would have to be highly subjective.    Are there other plant databases that have established such criteria?  Maybe we could borrow some of their logic and implement same for the genus 'Hosta'.   Something tells me this is either an all or none phenomena at best, and data that could be a sliding scale replete with data that could be very misleading, at worst.    If it could be constructed with a 1-5 level and understood to be very subjective, there might be some benefit that could accrue.   What do others think?  

Right now I'm passionate about getting ready for the 2004 AHS Convention, having but a moderate interest in genetic analysis of nematode resistance (genes) in Hosta.  I will say that there are many Hosta that appear to respond to nematode infestation with an increased presence of HS1(pro-1) and HS2 genes (or whatever resistance genes are present in Hosta).  One year, a plant will show a significant infestation and the next year the plant is either nearly immune or the nematodes have on sabbatical (as was the case for H. William Lachman, H. Summer Joy, H. Dorothy Benedict, H. Crayons, and others in one area of my garden that had been significantly infected last year).   Unfortunately, I am a gardener with a penchant for Hosta Science and not a Hosta Scientist with a penchant for gardening.  :-)

SO, if you want REAL answers, you'll want to ask your questions of nematologists or the technical support departments of the Agri-chemical companies. It's amazing how helpful they will be if you tell them you're interested in purchasing their products.  I found Bayer Agricultural to be most helpful but it took several emails and phone calls.  I finally did find a source for Nemacur that was willing to sell me one bag but it took going high up in the hierarchy and that bag had to be shipped here from Mississippi.  If I had wanted a truck load, however, it would have been no problem!      

RE>>Thanks much - I am sure many will benefit from this.
You're welcome much and  I hope so.  My best "advice", if you could call it that, is to NOT throw the baby out with the bath water as used to be recommended.  Let the plant develop it's natural defenses and if it dies, then you can report that this or that cultivar seems to be a real wimp in combatting nematodes.   Let us know how you do!  

Andrew Lietzow
in Des Moines, where we're likely to have our first hard freeze tomorrow evening--about 8 days ahead of the average first hard freeze date of Oct. 9.  

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