The Importance and Dangers of Pesticides and Herbicides

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 thesepesky weeds but they always seem to come back. This eventually led to development ofpesticides and herbicides. Herbicides allowed people to kill off the unwanted weeds. Over timethese herbicides became more and more specialized allowing them to only harm certain weeds asneeded 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 lessthan a foot high at the most, a plant that grows taller than that can get unlimited sunlight.

Theseplants will block the sunlight from the blueberries and rob them of nutrients found in the soil. Thiscompetition will inhibit the growth of the berries. This means less production and money for thegrowers. Many growers in areas of Maine such as Washington county could not afford to keeptheir fields in business.

Many acres of land went unused as a result of this and the local economywas 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 acheap and efficient way to rid crops of unwanted weeds. Many blueberry fields were reopenedwhich boosted the economy. This would be a great story if it ended there but unfortunately itdoesn’t because application was not regulated.

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Small traces of velpar were discovered in couple area wells. These traces were so small that they posed no threat to people, in fact theactual amount was about one half part per million.

The problem came from the fact that the wellbelonged to a school. Parents found out about this and people began to panic. People in theblueberry industry and others who had knowledge of pesticides knew that these amounts weren’tconsidered harmful, but others didn’t agree. It’s pretty hard to explain to a group of concernedparents that the water their child is drinking only has small traces of toxins in it and is safe todrink. Once the environmental activists in the area got word of this a decision was made to try toban Velpar. This met heavy resistance from the blueberry industry. After many hearings it wasagreed by both parties that Velpar shouldn’t be banned but should be regulated. The blueberryindustry decided to be in charge of regulate Velpar. They would control who had access to itand how it would be applied. They also put charcoal filters on wells which don’t allow Velar topass through. It is hoped that by controlling application to prevent future leeching, and filteringout existing traces, the problem can be controlled. Hexazinone really is an amazing pesticide.

When sprayed on crops it seeps into theground and is absorbed by the roots. Unfortunately the hexazinone that isn’t absorbed by theroots leaches through the sandy southern Maine soil into the ground water and we end up with situation like the one described above. The pesticide moves to the leaves where it blocks thephotosynthetic process. Without photosynthesis a plant literally starves and dies. The great thingabout hexazinone is that it doesn’t harm the blueberry plant. This means it can be applied directlyto the crop with great results. Hexazinone can also be sprayed in the spring when the plants donot 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 melting point of around 115 degrees Celsius. It is soluble in water as well as various otherchemicals including chloroform, methanol, and benzene. Hexazinone is stable in aqueoussolutions 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 pesticidedisposal 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 NPDESpermit. Do not discharge effluent containing this product to sewer systers without previouslynotifying the sewage treatment plant authority. For guidance, contact your State Water Board orRegional Office of the EPA.” In addition to the statement above more labels must appear. These statements talk moreabout 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 eyesor 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 wasbefore reuse.”Environmental hazard statement: “Do not apply directly to water or wetlands (swamp, bogs, marshes, and potholes). Donot 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 handtask. A person may enter the areas to perform other tasks only if the person is wearing thepersonal protective eye equipment listed on the label.” These labels help to release the producer of the pesticide from any liabilities. They alsohelp to ensure that the pesticide is used properly to avoid pollution. No human deaths or hospitalizations have been reported that were associated withhexazinone since 1976. Only one accident with the herbicide has been reported. That was acase of accidental indigestion. These statistics are due mostly to good judgment by people usinghexazinone. 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 levelsof toxicity. It is placed in oral toxicity category III, dermal toxicity category IV, inhalationtoxicity category III, and eye toxicity category I. Although it is harmful, it has been determinedthat hexazinone is not a mutagen in gene mutation.

After being sprayed on crops, hexazinone begins to work. It is absorbed either throughthe roots or leaves depending on the type of formulation and method of application. Hexazinonethen translocates upward through the xylem. It then acts as a photosynthetic inhibitor killing theweed. Herbicides such as hexazinone are a great importance to the blueberry and other farmingindustries. 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 peoplerealized that not as much Velar was needed to kill the weeds as previously thought. Newproducts are being develop at this very moment.

The use of Velpar has allowed the farmers andgrowers to cut back on the amount of pesticides and insecticides used because the habitats formost 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 leachinto the soil and contaminate wells but it will still kill weeds. Herbicides and pesticides whenused properly are a great asset to society.