FOLIAR NEMATODES |
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Not the
nastiest of the leaf problems, foliar nematodes are without a
doubt the most difficult to control and probably impossible to
eliminate. They are tiny wormlike things that get into the
leaves and begin sucking cells dry, eventually causing dead
areas between veins. They reproduce like crazy and a single
leaf could have thousands. When the leaf surface is wet some
come out and are washed off and spread to other plants. |
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They overwinter in dead leaves, the soil, and behind the dormant
buds of hostas. They also infest many other plants like ferns,
heucheras, coneflowers, rudbeckias, various weeds and even grasses.
By the end of the summer a garden could have millions. Checking
for nematode presence can be done with a cut-up leaf in water in a clear dish with a
5x magnifying glass and bright light.
There isn't a lot that can be done to control
them. The chemicals
that once worked were not for residential use and have mostly been banned
anyway. One that is effective, though very expensive, is Pylon.
Unfortunately it is not allowed for outdoor use. It can be used in
greenhouses or even taking plants into a garage for cleanup. Three
applications two weeks apart are necessary covering the leaves
completely. After Pylon, only contact-kill products are available -
nothing else can kill them in the plant. Strong hydrogen peroxide
sold as Zerotol works well, as does insecticidal soap. Drenching and
spraying with these as the plants begin to unfurl can greatly reduce
nematode damage.
More information on foliar
nematodes can be found HERE.
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In the
Garden: Pylon (indoors), Zerotol, Insecticidal Soap sprayed early
and repeated several times in the first 6 weeks after emergence
offers some control. |
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In the
Nursery: If allowed, Vydate offers the best control. Spraying or
dipping with Pylon can clean up plants, and potting soil and all
surfaces can be cleaned with Zerotol. |
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Note:
There is a bacterial leaf disease that causes very similar symptoms.
It is difficult to tell which is which just from visual examination.
Treatment is different for the two problems. Article HERE. |
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