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Re: Question for Dr. Grewal

  • Subject: Re: Question for Dr. Grewal
  • From: njhosta@hotmail.com
  • Date: Wed, 9 Jan 2002 16:58:37 -0500
  • Wrom: QTIPWIGYOKSTTZRCLBDXRQBGJSNBOHMKHJ

       I've noticed that in hostas that receive a lot of direct sunlight,
nematode damage in the upper, more exposed leaves is rarely seen. If the
plant is infested the damage shows only on leaves that are shaded by the
outer leaves. This would indicate that they are sensitive to the
temperatures that can develop in a leaf that is heated by the sun, and will
avoid those leaves. It would also seem to indicate that they can move
through the plant down at the crown level, where the leaves join. Would you
say this is so? Or are they randomly entering leaves and only reproducing
successfully where the temps stay cooler? Do you think impromptu treatments
such as leaving infested plants on a black driveway for a few days in hot
weather or putting them inside closed cars in same would have much effect?
Are different stages destroyed at different temperatures?
        If you're not tired of answering, one more---- What possibility is
there of nematodes spreading around a garden carried by animals running
through wet leaves after a rain? This seems a possibility to me if
populations are high and thriving in one area, and a strong argument for
treating immediately when you first discover them.
        Sorry about the endless string of questions, but many hosta
gardeners still think they are harmless and not worth bothering to treat
for. I have been breeding hostas and collecting sports for some time now, so
disposing of plants, especially seedlings, is not a choice.

...........Bill



> Bill,
>
> I replied to a very similar question yesterday.  I hope you got the answer
> to your question.  The nematodes become active soon after the plants start
> sprouting. Due possible injury (phytoxicity) to young plants, I would wait
> spraying until early May.
>
> Parwinder
>
> At 02:16 PM 01/08/2002 -0500, you wrote:
> >Another thing most people seem confused about is when in the spring they
> >become active. Because symptoms do not show in hosta until midsummer, it
is
> >impossible to tell without a microscope if a plant or bed is infested.
This
> >causes most gardeners to think in terms of beginning control measures at
> >that time. When do nematodes come out of dormancy in the spring, and when
> >should treatment begin?
> >
.........Bill
> >Meyer
> >
> >
> > > Yes, the rate of spread is about right and it depends mainly on the
soil
> > > type, slope and water.
> > >
> > > No nematicide provides 100% control of nematodes, but there are no
reports
> > > on the development of resistance in nematodes under field
> > > conditions.  Furthermore, the mode of action of ZeroTol is such that
> > > resistance development is not really possible.
> > >
> > > Regular applications of ZeroTol to infected plants will reduce spread
of
> > > the nematodes in a garden.  Plucking of infected leaves as soon as the
> > > symptoms of nematode infection become clear followed by a thorough
> > > clean-out in the fall can substantially reduce nematode spread.
> > >                 - Parwinder Grewal
> > >
> > > At 01:13 PM 01/08/2002 -0500, you wrote:
> > > >Hi Dr.Grewal,
> > > >              Thank you for answering. From what I've seen, they seem
to
> > > >spread at a rate of about ten feet a year in all directions, more if
> > > >downhill. Would this seem about right? Your findings indicate that
> >ZeroTol
> > > >kills about 80% when plants are in the ground, if I remember right.
Would
> > > >this make it likely that a resistant strain would develop? Also would
> >using
> > > >ZeroTol regularly control the spread, or would they continue to
spread
> > > >through the rest of the garden at more or less the same rate?
> > > >
> > > >.........Bill Meyer
> > > >
> > > >
> > > > > Hi Bill,
> > > > >
> > > > > I know that most effective nematicides are no more available to
> >control
> > > > > foliar nematodes and there are many restrictions the use of other
> > > > > chemicals.  In our research, we have discovered that ZeroTol,
which is
> > > > > currently used as a general sterilant/fungicide, is an effective
> > > >nematicide
> > > > > against foliar nematodes.  This chemical can be applied by home
> > > > > owners.  Our findings on ZeroTol and other chemicals to
> >control/suppress
> > > > > foliar nematodes were published in the Spring issue of Hosta
Journal
> >in
> > > > > 2001.  There are also other useful tips and preventive measures
> >described
> > > > > in that article.
> > > > >
> > > > > Yes, foliar nematodes can eventually kill hosta plants if they are
> >ignored
> > > > > for long.  Overtime nematode populations build up on plants and in
the
> > > >soil
> > > > > around plants.
> > > > >
> > > > > Parwinder Grewal
> > > > > Assistant Professor
> > > > > Department of Entomology
> > > > > OARDC
> > > > > The Ohio State University
> > > > > 1680 Madison Ave
> > > > > Wooster, Ohio 44691, USA
> > > > > Phone (330) 263-3963
> > > > > Fax (330) 263-3686
> > > > >
> > > > >
> > > > > At 11:31 AM 01/08/2002 -0500, you wrote:
> > > > > >Hi Dr. Grewal,
> > > > > >           A question that is commonly asked on the lists is what
can
> >the
> > > > > >average gardener who does not have access to restricted chemicals
> >like
> > > > > >Nemacur do about foliar nematode infestation. Because of changes
in
> >the
> > > > > >pesticide laws, many of us find ourselves with these pests
running
> > > >rampant
> > > > > >and we are not permitted to use the chemicals that best control
them.
> > > >What
> > > > > >would you say is the most effective treatment we could use?
> > > > > >           Another somewhat related question is ------What would
you
> >say
> > > >the
> > > > > >long-term effects on hosta are of untreated or poorly treated
foliar
> > > > > >nematode infestations? Can they kill plants eventually?
> > > > > >
> > > > > >..........Bill Meyer

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