hort.net Seasonal photo, (c) 2006 Christopher P. Lindsey, All Rights Reserved: do not copy
articles | gallery of plants | blog | tech blog | plant profiles | patents | mailing lists | top stories | links | shorturl service | tom clothier's archive0
 Navigation
Articles
Gallery of Plants
Blog
Tech Blog
Plant Profiles
Patents
Mailing Lists
    FAQ
    Netiquette
    Search ALL lists
    Search help
    Subscription info
Top Stories
Links
sHORTurl service
Tom Clothier's Archive
 Top Stories
Disease could hit Britain's trees hard

Ten of the best snowdrop cultivars

Plant protein database helps identify plant gene functions

Dendroclimatologists record history through trees

Potato beetle could be thwarted through gene manipulation

Hawaii expands coffee farm quarantine

Study explains flower petal loss

Unauthorized use of a plant doesn't invalidate it's patent

RSS story archive

Re: Question for Dr. Grewal

  • Subject: Re: Question for Dr. Grewal
  • From: Parwinder Grewal <grewal.4@osu.edu>
  • Date: Fri, 11 Jan 2002 09:22:51 -0500

Hi Bill,

Thanks to the current AHS President Clarence Falstad who invited me to work 
on the foliar nematode problem.

I agree that the foliar nematode problem is widespread and it difficult to 
contain due to the movement of plants.  The ability of nematodes to survive 
in soil and reproduce on soil fungi make it very difficult to eliminate the 
nematodes or enact any effective quarantine regulations.

Yes several ornamentals are susceptible to foliar nematodes.  There are 
three major nematode species, Aphelenchoides fragariae, A. ritzemabosi, and 
Ditylenchus dipsaci that infect ornamentals.  Although, we found only A. 
fragariae in our surveys, it is possible that A. ritzemabosi can also 
infect hostas.  I do not think at this point that we need different control 
methods for these other nematodes.

Yes, the foliar nematodes are a pest of strawberries too.  Although, I have 
not worked with strawberries yet, I would expect that the nematode symptoms 
may be more common on the lower (less exposed) leaves.  The name of the 
nematodes reflecting strawberries is merely due to the fact that the 
nematode was originally described from this host.

Although, difficult to prove for certain, it is likely that the use of 
broad spectrum chemicals in the past had kept foliar nematode incidence to 
a minimum.  I would expect that in future more specific nematicides that 
would be effective against foliar nematodes will be discovered.  It is also 
expected that more emphasis will be placed on the development of preventive 
measures and bio-based pesticides.

Parwinder


At 11:08 AM 01/10/2002 -0500, you wrote:
>Hi Parwinder,
>           It's a pleasure to have someone to ask the questions to. To have
>someone with your knowledge and experience with nematodes step into hosta
>circles is a real help to those of us who know hostas but not nematodes.
>Over the last five years or so foliar nematodes have spread like a biblical
>plague through the community of hosta collectors and breeders. The rule
>before was always free exchange of plants with little to worry about with
>pest transmission. Now many nurseries both wholesale and retail routinely
>sell nematode infested plants to their customers, largely because of timing.
>They get stock in and watch it most carefully during the time of year that
>nematode damage doesn't show and pay much less attention later in the summer
>when sales slack off. By then, many more infested plants have been sold. The
>atmosphere now is one of secret words being passed about which nursery has
>them and which ones don't. From what I've seen personally, as many as half
>do.
>           OK, more questions. Dan Nelson and I were at Alex Summers' garden
>one day in September when I noticed that there was a large planting of
>anemones (at least five years old) that appeared to be heavily infested with
>foliar nematodes. Dan then noticed that the hostas rubbing leaves with them
>were not showing any signs of infestation, although both groups of plants
>were growing together for years. Is this the same nematode? Are their more
>than one species of nematode causing problems in hosta, and if so, would
>there be different treatment for each?
>            Another question comes from the ones you just answered. If the
>nematode found in hosta is named for strawberry plants, I would assume it is
>a serious pest for strawberry crops. In hostas these nematodes don't do well
>if there is a lot of sunlight and heat on the plant, but strawberries are
>grown in full sun. Any idea what this would mean?
>           Is there any relief in sight as far as the government goes in
>allowing effective chemicals to be used at least in nurseries to stop this
>growing problem? These days I think more hosta gardens have nematode
>problems than not, and the situation is worsening each year, as more and
>more people buy or trade infested plants. Hosta societies from the local
>level to the national are very dependent upon the revenue raised by plant
>auctions and sales, and the likelihood now is that several (at least)
>infested plants are passed at every one. It has been suggested that this
>problem was caused by the government-mandated move away from broad-spectrum
>pesticides to more specific ones, before effective specific ones were
>developed. Can we expect better pesticides in the near future, both for
>nurseries and home use?
>
>.........Bill Meyer
>
>
> > Bill,
> >
> > You have made some excellent observations on the exposure of nematode
> > infected hostas to the sun.  I have made similar observations also.  In
> > fact there are two factors, temperature and ultraviolet (UV) radiation
>that
> > affect nematodes.  Nematodes are very sensitive to ultra violet
> > radiation.  In our tests with UV light emitted from a lamp in the
> > laboratory, most nematodes were killed in the leaves with just one hour
> > exposure.  Thus putting nematode infected hosta plants in the sun (exposed
> > areas) is likely to reduce nematode infection.  If most leaves are
>exposed,
> > it could actually cure the plants of nematode infection.  We are doing
>such
> > experiments.
> >
> > Yes, temperature could be important as well, but hot temperatures may also
> > kill the plant, so I would not recommend to place plants in closed
> > cars.  Exposure of plants to the sun on driveways for a few days is a good
> > idea.
> >
> > Yes, the nematodes have the ability to move up and down the plant, but you
> > are also right that successful reproduction occurs only under favorable
> > temperature and minimal UV light.
> >
> > Yes, different stages of nematode life cycle show differences in tolerance
> > to temperature and nematicides.  Eggs are most tolerant.  Nematodes in the
> > dry leaves can enter into what we call anyhydrobiosis (life without water)
> > and then become very tolerant of both the high and low temperatures.  This
> > is one of the ways this nemtaode can survive in the dry plant material.
> >
> > It is possible that animals moving through wet plants can carry nematodes
> > and aid in their dispersal in the garden, but I shall not consider them as
> > the major source of dissemination.  Perhaps the biggest source would be
> > water (rains, floods, and watering).  Treating plants as soon as the
> > nematode symptoms become evident is always a good idea.
> >
> > Keep firing away the good questions.
> >
> > Parwinder Grewal
> >
> > At 04:58 PM 01/09/2002 -0500, you wrote:
> > >        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
> > >
> > >---------------------------------------------------------------------
> > >To sign-off this list, send email to majordomo@mallorn.com with the
> > >message text UNSUBSCRIBE HOSTA-OPEN
> >
> > ---------------------------------------------------------------------
> > To sign-off this list, send email to majordomo@mallorn.com with the
> > message text UNSUBSCRIBE HOSTA-OPEN
> >
>---------------------------------------------------------------------
>To sign-off this list, send email to majordomo@mallorn.com with the
>message text UNSUBSCRIBE HOSTA-OPEN

---------------------------------------------------------------------
To sign-off this list, send email to majordomo@mallorn.com with the
message text UNSUBSCRIBE HOSTA-OPEN





 © 1995-2015 Mallorn Computing, Inc.All Rights Reserved.
Our Privacy Statement
Other Mailing lists | Author Index | Date Index | Subject Index | Thread Index