Most hosta collectors are aware of the problems
foliar nematodes can cause in a hosta patch. I'd like to share with you my
method for controlling foliar nematodes in my hosta collection of 650 cultivars
consisting of 3000 plus individual crowns.
For starters I strongly believe in physical
isolation of foliar nematode infested hosta crowns. Each and every hosta that I
find with nematodes I remove from my main hosta garden and isolate them in a
separate garden I call my nematode bed. This hosta bed is separated by 400 feet
from my mail hosta patch. I always leave the hoe I use for weed control in this
hosta bed and I'm very careful never to work in my nematode bed and then work in
my main hosta garden.
When I find a foliar nematode infested hosta here's
what I do.
1) I Immediately dig and move the hosta with as
much soil as I can to my nematode bed.
2) I check very closely all neighboring hostas and
remove the leaves that were closest to the infected plant. The leaves I remove
from these neighboring hostas show no sign of nematode damage. If they do
show nematode damage of course they too get moved to the nematode
3) I place a 4 foot yellow fiberglass rake handle
in the ground where the infected hosta was growing. I then spray a 10 foot
diameter circle centered on this yellow marker with Oxmyl or Nemacur 3 doing a
good foliar application and soil drench at the same time.
4) I check the hostas near this marked area
regularly for any further signs of foliar nematodes.
If I have the same hosta in another area of the
garden that came from a different source I throw away the infected hosta unless
it is one with a high value. If I have several crowns of the same cultivar that
are infected I throw away all but one of these hostas and move the infected
hosta to the nematode bed. I believe that inexpensive hostas that have foliar
nematodes should be thrown away. By thrown away I mean placed in a garbage bag
to be collected by a trash hauler.
Here's the protocol I use on my nematode
1) June 1st I foliar spray and soil drench my whole
nematode bed with Oxmyl or Nemacur 3. I use 40 gallons of mix on a bed that's
approx 1,000 square feet in size. I also spray a 10 food diameter circle marked
by my yellow rake handles in my main garden.
2) June 15 (two weeks later) I repeat this
3) June 30 (two weeks later) I repeat this
application for the third time.
4) July 15 (two weeks later) I repeat this
application for the fourth time.
4) July 30 (two weeks later) I repeat this
application for the fifth time.
My goal is to kill the foliar nematode in it's
adult stage. My reason for repeated applications is to give all nematode eggs a
chance to hatch and catch them in their adult stage with a spray
application. My hope is that after 5 applications almost all nematode eggs and
or nematodes in their dormant stage would hatch or become active and
vulnerable to the spray application. I time the first spraying June 1st figuring
that environmental conditions are right for all eggs to hatch (warm weather) and
for all dormant stages to become active (warm weather). It is my understanding
that eggs and dormant stage nematodes may not be killed by spray
I came up with this protocol myself based on what I
have heard and read on the life cycle of the foliar nematodes that affects
hostas. I'm using restricted use chemicals that are not available to most home
gardeners and they are not available for a good reason. These chemicals are
dangerous and need to be handled and applied using the correct personal
protection equipment and application methods.
Dr. Grewal has found less toxic or non-toxic
chemicals or controls for foliar nematodes in hostas and I suggest a protocol
similar to mine for their application. I of course would gladly change my
methods for nematode control and am anxious for Dr. Grewal's input.
P.S. My nematode bed was not treated in 2001 and no
signs of foliar nematode activity was noticed. I realize of course that I may
still have small numbers of foliar nematodes that are not at a high enough
population level to show physical damage to the hosta leaves.