Glyphosate, or Roundup:
Roundup is the original commercial name for a broad-spectrum herbicide - meaning it works on just about anything that absorbs it - using glyphosate. Patented in the 1970's by the US company, Monsanto, the patent ran out in 2000, and now many companies, including Du Pont, Dow AgroSciences, and Platte, use glyphosate to make herbicides. It is the most common active ingredient in herbicides used in the US today. Plants must absorb the isopropylamine salt of glyphosate through their foliage before it will kill them. It is systemic, and is only effective on plants with leaves or exposed cambium, the inner growing bark, and tender exposed roots, thus it won't work as a pre-emergence herbicide. In other words, you can't spray the ground with it, and keep weeds from growing there. It works well on woody and leafy plants, but does not affect conifers much. It won't work on cactus or other plants with a waxy coating on the surface of their leaves because it runs off before it is absorbed.
Glyphosate is available in concentrate solutions and also as salts. There are many different versions of herbicides with glyphosate as the active ingredient that have different additives such as surfactants to make it stick to the leaves and such. It can be used to control pond vegetation and is available in herbicides like Aquaneat and Aquamaster, and is not toxic to fish; but many common glyphosate solutions, including Roundup, are poisonous to fish because of the additives in them, therefore you must consider run-off for certain mixtures of glyphosate before you apply it. It can be applied to freshly cut stumps, but it won't be effective on woody bark because it has to be taken up by the plant. It isn't very effective on some clover species.
The way glyphosate works is that when it is taken up by the plant and transferred to it's growing points, it inhibits an enzyme that the plant uses to make certain necessary amino acids. Since the herbicide has been in use for so long, many studies have been done on it to see how it might affect people and animals in the long term. So far, all studies show that it is very safe, as glyphosate does not affect animal amino acid uptake because animal bodies use a different amino acid pathway than plants. For a sample of studies on it, just google the name glyphosate and look at the footnotes. There will be several pages listing the universities and organizations that have studied it. It is not toxic to bees. It has no significant potential to become residual in animal tissue. Since it is an acid it is an eye irritant, however, but shows no affect on animals or pets by accidental exposure unless they drink it, and then it's the additives used that harm more than the glyphosate. Certain additives in some glyphosate herbicides has shown some detrimental effect on land birds like quail. Certain additives in glyphosate herbicides can be poisonous to fish and amphibians as mentioned above. It's affect on soil micro-organisms is limited because it rapidly bonds to soil particles, and is not taken up readily by the micro-organisms. It does affect earthworms some because it is an acid, and they are so sensitive, but since it very readily bonds to soil particles, it's effect on them is negligible with normal use. It is very water soluble, easily diluted, and is less effective if applied to wet plants. Rain can wash it off before the plant takes it up. Most of the herbicides using glyphosate need to be on the plant for 24 hours before water cannot wash it off.
The main controversy over glyphosate use has to do with residue in the soil. The time it takes for it to break down depends upon the average annual temperature. For it to breakdown into half its original concentration is called its half-life. In Texas, its half-life is from 3 days to 6 months. In Sweden, glyphosate is still present in the soil, albeit bonded there, from 1 - 3 years.
Organic farmers cannot use it because it is a synthetic chemical. (Soap is too, but that additive to sprays is not banned, although it is a strong alkali and the phosphorous in many soaps, especially dish washing soap, causes a fatal algae bloom on water sources, and is very harmful to earthworms, amphibians, and fish in concentrated amounts. Earthworms are also very sensitive to citrus oil, which is another common organic additive. Familiarity breeds contempt.)
Glyphosate seems to be the perfect herbicide saving farmers millions of dollars in tillage thus conserving fuel and conserving the soil from erosion at the same time. But since it has been in use for so long, some plants are showing glyphosate resistance through long exposure and mutation. Just like roaches to an insecticide, plants can become resistant to an herbicide, too. The problem is coming up with another safe herbicide. Weed control has always been a problem for mankind in food production. The use of an herbicide to kill grasses and weeds, and then planting directly into the dead groundcover is called no-till farming. In the past, tillage, controlled burning, mulching, and hand-weeding were the only alternatives. All of these methods are labor intensive, and these do not work so well with plants that grow by invasive rhizomes, such as Johnson Grass and crabgrass.
Constant tillage is not only very expensive in human effort, compacts the soil, and destroys much important mycorrhizal fungi, but worst of all, tilled land is very susceptible to wind and water erosion, which has poisoned our rivers, and ruined our fields. Any archeologist or anthropologist can point out many civilizations that expired due to soil erosion. Soil erosion is still our greatest enemy for food production, and is happening in the US and around the world at an alarming rate. It seemed that the use of no-till farming practices using a safe herbicide was the perfect solution. But in nature, mutations will occur, resulting in survivors with a built-in resistance. Now we will have to deal with resistance not only in antibiotics and insecticides, but also in plants resistant to herbicides like glyphosate. If we are not careful, mankind's greatest advances in food production and controlling disease will be nullified due to natural genetic mutations.
For more research upon glyphosate click on the links browser button on the top of the home page.