Concerns about herbicide use to control hydrilla

I decided to include in my wordpress blog articles and information on ecological issues that are of concern. Often I will post friends articles.  You will come to know how ecological thinking enters my life. Below is an guest editorial by my friend Brian Caldwell that appeared in the Ithaca Journal June 2, 2012.


The presence of hydrilla in the Cayuga Inlet is a reason for concern.
However, we should avoid the end-of-the-world-as-we-know-it
characterizations that have clouded discussions of this weed. We need to
think carefully before making blanket applications of herbicides to our
drinking water.

My knowledge of this issue comes not as a boater or fisherman, but as an
organic farmer. I have hesitated to speak out, but aquatic herbicides
affect all of us. Along with other organic farmers, I have produced
crops for many years without herbicides. I also know that eradication of
weeds is extremely unlikely, whether by chemical or other means.

Eradication of hydrilla may be possible in small isolated ponds, but not
in an established infestation in a large, open water system such as the
Inlet and Cayuga Lake. Undoubtedly, hydrilla will persist and spread in
spite of the application of hundreds of thousands of dollars of
herbicide, low levels of which will flow into drinking water via the
Bolton Point water plant. In the meantime, the herbicides endothall and
fluridone will kill vegetation and aquatic life. For instance, the
target endothall concentration of 2-3 ppm has been shown to kill over
50% of the one toad species tested. Endothall effects on some aquatic
species do not appear serious at that level, but others, including some
species of zooplankton, are killed at much lower rates. Of course, most
exposed non-target plants will also be killed. If we apply herbicides
over the expected 10+ years, we will profoundly change the aquatic
communities of the lower Inlet and nearby areas of Cayuga Lake.

It is worth noting that the 2012 Local Hydrilla Task Force draft work
plan’s goal is to reduce hydrilla biomass by 98%. The remaining 2%, if
untreated, will quickly grow back. This puts us on a pesticide treadmill
very similar to that of many farm fields, where weeds are not
eradicated—they are sprayed every year.

It is also worth noting that weeds, whether terrestrial or aquatic,
require nutrients to grow. Phosphorous additions to surface water from
sources such as soil erosion and sewage treatment plants strongly
stimulate aquatic weed growth. It likely that if we work harder on
reducing the levels of phosphorous in our surface water, the rank growth
of hydrilla and other water weeds will be reduced. In fact, harvest and
removal of water weeds is a good way of reducing excess nutrient levels
from surface water. Harvest of hydrilla presents a problem, because cut
filaments from the harvest process can float downstream and re-root. In
a confined area like the Inlet, would it be possible to catch such
filaments in a net before they spread?

Harvest (as is done Florida and Virginia) may be one component of a
long-term sustainable approach to managing hydrilla and cleaning up our
surface water. What others can we think of? We may as well start
implementing them now, rather than putting pesticides into our drinking
water and wasting millions of dollars on futile attempts at eradication

Brian Caldwell
West Danby, NY



About lew60

Trained in ecological sciences agroforestry, horticulture and landscape ecology. Pomologist. Sculptor and woodcarver.
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