The Rural Voice, 2001-03, Page 34By Rhea Hamilton -Seeger
Last October I wrote to you about
some solutions to a powdery
mildew/fungi that had been leaving
some of our young majestic maples
looking rather worse for wear.
Among the recommendations I made
was to look into using a fungicide
called benomyl.
After the column was printed I had
a call from a concerned reader who
pointed out some problems associated
with using benomyl in the treatment
of this fungus. So I went back to my
sources of information, Rodale's
Garden Problem Solver and the
Ontario Ministry of Agriculture,
Food and Rural Affairs Publication
96 entitled The Gardener's
Handbook, An Integrated Approach
to Insect and Disease Control. The
Gardener's Handbook recommended
benomyl and Rodale's organic
approach only suggested a very
careful application of copper
sulphate, lime sulfur or sulfur. No
mention of benomyl in this 1988
book. And then I hit the internet.
The Fact sheets I found there were
published by Pesticide News, a
journal of the Pesticides Trust in the
UK and Extoxnet, an extension
toxicology network put together by
the Universities of Cornell, Michigan,
Oregon State and California with
funding from the U.S.A. Agricultural
Pesticide Impact Assessment
Program.
Benomyl was first referred to in
1968 and introduced onto the UK
market in 1971 by the U.S. company
Du Pont. It is a systemic
benzimidazole fungicide that is
strongly bound to soil and does not
dissolve in water.
It is widely used to fight fungus
diseases in vegetable crops, apples,
soft fruits, nuts, ornamentals,.
mushrooms, lettuce, tomatoes and
turf.
It is available to the gardener
under the trade name of Benlate.
When applied to turf it has a half life
of three to six months and when
applied to bare sod the half-life is six
to twelve months. Since benomyl is a
systemic fungicide, it is absorbed by
30 THE RURAL VOICE
Gardening
Clean out the chemicals
plants through their roots or the
above ground tissues. Once it is in the
plant it accumulates in the veins and
leaf margins. From a scientific point
it is quite stable and will remain as
the parent compound for one to 23
days before it degrades or breaks
down into carbendazim (MBC)
which is considered relatively non-
toxic .
But let's look closer at some of the
facts around benomyl. It is
selectively toxic to micro-organisms
and invertebrates. especially
earthworms. This is a clue that we
have a problem. I want to encourage
these natural composters in my
garden as well as some of the other
micro organisms that help with
decomposition.
But it gets worse. Benomyl came
under fierce scrutiny in the early
1990s when pregnant women were
exposed to benomyl and subsequently
gave birth to children with eye
defects. In 1993, The Observer, a
British National newspaper,
published the first in a series of
articles alleging a possible link
between exposure of pregnant
mothers to benomyl and their
children being born without eyes
(anophthalmia ) or with related
syndromes including reduced eyes
and blindness due to severe damage
of the optic stem. The newspaper
cited a number of suspected clusters
in the UK that may have
corresponded to areas of benomyl
use. There was an assessment done
but it was concluded that it was
doubtful there was a
link.
The Ministry of Agriculture
Fisheries and Food (MAFF) in Great
Britain, says that since chronic effects
are brought about by exposure to
unusually high doses of the fungicide
and that people are unlikely to
receive such high doses, that the
conclusion is that it is safe. As a
consumer I believe that if there is any
doubt about the safety of this
chemical then it should be shelved.
An alternative is being developed,
azoxystrobin. It is based on a natural
fungicide and may prove to be safer
than benomyl. Which draws another
question to mind: is there such a
chemical that can be called a natural
fungicide? Somehow we have this
idea if a chemical is labeled
"'natural" it must be safe. It is a
notion that we naively cling to.
We have had cases of children
born with defects in this province and
there are people out there trying to
educate the public about the hazards
and tragedies that can be caused by
misuse, overuse and abuse of
chemicals. There is a reason why
gardeners try to look for organic or
non -chemical approaches to problems
in the garden. The perfect garden
does not necessarily mean one
without its share of problems. A bit
of fungus, an infestation of sap -
sucking insects or a nibbler here or
there is not an issue in light of the big
picture. The challenge is to take a
hard look at your problems in the
garden and decide if a change in
conditions will alleviate your
problem with a particular disease or
look at encouraging a few more birds
to clean up an over population of
insects.
The story of benomyl is enough to
show us that not all packaged
solutions are worth the price we
pay.0
Rhea Hamilton -Seeger and her
husband raise two children at their
home near Auburn. She is a skilled
cook and gardener.
The deadline
for the
April issue of
The Rural Voice
is
March 14, 2001