As long as the human race has been cultivating the
soil, we have had to deal with other vegetationthat ends up competing with the crops. People have tried many methods to get rid of these
pesky weeds but they always seem to come back. This eventually led to development of
pesticides and herbicides. Herbicides allowed people to kill off the unwanted weeds. Over time
these herbicides became more and more specialized allowing them to only harm certain weeds as
needed such as broad leaf killers. One of these specialized herbicides known as hexazinone.
Hexazinone is used in the blueberry industry. Since low-bush blueberries only grow less
than a foot high at the most, a plant that grows taller than that can get unlimited sunlight. These
plants will block the sunlight from the blueberries and rob them of nutrients found in the soil. This
competition will inhibit the growth of the berries. This means less production and money for the
growers. Many growers in areas of Maine such as Washington county could not afford to keep
their fields in business. Many acres of land went unused as a result of this and the local economy
was quickly declining.
In the early 1980’s all this changed. The herbicide hexazinone was introduced.
Marketed by DuPont under the name Velpar, it was the savior to a dying industry. It was a
cheap and efficient way to rid crops of unwanted weeds. Many blueberry fields were reopened
which boosted the economy. This would be a great story if it ended there but unfortunately it
doesn’t because application was not regulated. Small traces of velpar were discovered in a
couple area wells. These traces were so small that they posed no threat to people, in fact the
actual amount was about one half part per million. The problem came from the fact that the well
belonged to a school. Parents found out about this and people began to panic. People in the
blueberry industry and others who had knowledge of pesticides knew that these amounts weren’t
considered harmful, but others didn’t agree. It’s pretty hard to explain to a group of concerned
parents that the water their child is drinking only has small traces of toxins in it and is safe to
drink. Once the environmental activists in the area got word of this a decision was made to try to
ban Velpar. This met heavy resistance from the blueberry industry. After many hearings it was
agreed by both parties that Velpar shouldn’t be banned but should be regulated. The blueberry
industry decided to be in charge of regulate Velpar. They would control who had access to it
and how it would be applied. They also put charcoal filters on wells which don’t allow Velpar to
pass through. It is hoped that by controlling application to prevent future leeching, and filtering
out existing traces, the problem can be controlled.
Hexazinone really is an amazing pesticide. When sprayed on crops it seeps into the
ground and is absorbed by the roots. Unfortunately the hexazinone that isn’t absorbed by the
roots leaches through the sandy southern Maine soil into the ground water and we end up with a
situation like the one described above. The pesticide moves to the leaves where it blocks the
photosynthetic process. Without photosynthesis a plant literally starves and dies. The great thing
about hexazinone is that it doesn’t harm the blueberry plant. This means it can be applied directly
to the crop with great results. Hexazinone can also be sprayed in the spring when the plants do
not have leaves and it will still kill them later on.
The chemical formula for hexazinone is: 3-cyclohexyl-6-(dimethylamine)-1-methyl -1, 3,
5-triazine 2,4(1H, 3H)-dione. Hexazinone is a crystalline solid and white in color. It has a
melting point of around 115 degrees Celsius. It is soluble in water as well as various other
chemicals including chloroform, methanol, and benzene. Hexazinone is stable in aqueous
solutions at a pH of five, seven, and nine at a temperature of up to 37 degrees Celsius.
When hexazinone is sold as an herbicide warning labels are required to be placed on it.
This labels are warnings that tell how to use and dispose of the product. The following pesticide
disposal statement must appear on hexazinone manufacturing-use products:
“Do not discharge effluent containing this product into lakes, streams, ponds, estuaries,
oceans, or public waters unless this product is specifically identified and addressed in an NPDES
permit. Do not discharge effluent containing this product to sewer systems without previously
notifying the sewage treatment plant authority. For guidance, contact your State Water Board or
Regional Office of the EPA.”
In addition to the statement above more labels must appear. These statements talk more
about application and safety. The following must appear on end-use products:
In the precautionary statements:
“Corrosive, causes irreversible eye damage. Harmful if swallowed. Do not get in eyes
or clothing. Mixers, loaders, and applicators must wear goggles, face shield, or safety glasses.
Wash thoroughly with soap and water after handling. Remove contaminated clothing and was
Environmental hazard statement:
“Do not apply directly to water or wetlands (swamp, bogs, marshes, and potholes). Do
not contaminate water when disposing of equipment washwaters.”
In the directions for use section:
“Do not enter or allow entry into treated areas until sprays have dried to perform hand
task. A person may enter the areas to perform other tasks only if the person is wearing the
personal protective eye equipment listed on the label.”
These labels help to release the producer of the pesticide from any liabilities. They also
help to ensure that the pesticide is used properly to avoid pollution.
No human deaths or hospitalizations have been reported that were associated with
hexazinone since 1976. Only one accident with the herbicide has been reported. That was a
case of accidental indigestion. These statistics are due mostly to good judgment by people using
Tests have been done on hexazinone to measure its oral, dermal, and inhalation toxicity.
Most of these tests have been conducted on rats and rabbits. All these tests yielded high levels
of toxicity. It is placed in oral toxicity category III, dermal toxicity category IV, inhalation
toxicity category III, and eye toxicity category I. Although it is harmful, it has been determined
that hexazinone is not a mutagen in gene mutation.
After being sprayed on crops, hexazinone begins to work. It is absorbed either through
the roots or leaves depending on the type of formulation and method of application. Hexazinone
then translocates upward through the xylem. It then acts as a photosynthetic inhibitor killing the
Herbicides such as hexazinone are a great importance to the blueberry and other farming
industries. We need to work to regulate the use of these products to ensure a clean environment.
By studying these herbicides we can find better ways to use them. In the early 90’s people
realized that not as much Velpar was needed to kill the weeds as previously thought. New
products are being develop at this very moment. The use of Velpar has allowed the farmers and
growers to cut back on the amount of pesticides and insecticides used because the habitats for
most of these bugs were in the weeds. DuPont recently came out with a fertilizer called Pronone.
This comes in a pellet form and only has small amounts of Velpar in it. The Velpar will not leach
into the soil and contaminate wells but it will still kill weeds. Herbicides and pesticides when
used properly are a great asset to society.