Weed seeds constitute one of the principal devices for invasion of weeds into new areas. Because of this fact seed laws require that the amount and kinds of weed seeds be indicated on the label attached to seeds offered for sale. In many states and provinces excessive amounts of noxious weed seeds per unit weight may be the basis for the prohibition of sale of otherwise acceptable seed.

Many factors influence the effectiveness of a herbicidal spray. The importance of some, such as herbicide formulation and carrier, has been demonstrated, while the influence of others is either in doubt or has not been established. Since selective herbicides are being applied as sprays to millions of acres annually, more information on factors influencing their effectiveness in spray applications would be of value.

It has long been recognized that one of the inherent problems in spray application, particularly with airplanes, is that of droplet size control. It is not generally known which droplet sizes or ranges of droplet sizes are the most effective biologically for the various types of treatments. It is known, however, that excessively large droplets result in a serious waste of material, and that very small droplets present a serious drift problem. For these reasons, spray droplet size and the range of sizes in a given spray have become important criterions in evaluating a spray distribution pattern.

Since the advent of the new and, generally, more efficient herbicides, a great deal of research has been done and a voluminous literature presented concerning their uses and possible mechanisms of action. The more obvious effects of the chemicals have been described at length but the basic physiological mechanisms remain relatively undefined.

The compound 3-amino-1, 2,4-triazole (ATA) is water soluble, heterocyclic and will react with most acids and bases to form salts. Several workers have reported that ATA is a promising herbicide for the control of a number of weed species. ATA was first noted to have defoliating and regrowth-inhibiting properties on cotton in tests conducted by workers of the Texas Agricultural Experiment Station in 1952. The compound was found to increase the effectiveness of many commercial defoliants while adding the property of regrowth inhibition. During 1954 and 1955, a number of tests were conducted with various salts and derivatives of ATA in the hope that they would be more effective at lower rates as cotton defoliants and regrowth inhibitors. The present paper compares the performance of ATA with eight of its salts or derivatives which were found to be the most successful in defoliating cotton and controlling regrowth after preliminary screening in the greenhouse.

When a small seed is covered with an inert material which makes it relatively large and round, it is called a pelletized seed. The main advantage in using pelletized vegetable seeds is that they can be planted at regulated distances from each other. This decreases the number of doubles and makes thinning easier and cheaper. If perfect seed germination and seedling survival were possible, pelletized seed could be planted at the distance required for each crop and thinning could be eliminated. This is impossible in practice, however, and more seeds than are required for final stand must be planted. As a result, thinning is necessary. This is usually done by hoeing out the extra plants. Weeds in the rows are removed at the same time.

Since 1951 a number of reports on the use of pre-emergence herbicides for cotton have been published, and in several cases, these reports included data on the reduction of hand labor following the use of chemicals. In 1956, McWhorter et al. reported that combining chemical treatments with cross-plowing resulted in even greater reductions of hand labor than by the use of chemicals alone. They also reported that even though the amount of hand labor was reduced, both by the use of chemicals alone and by a combination of chemical and mechanical means, a corresponding reduction in the overall weed control cost did not always occur.

The use of pre-emergence herbicides to aid in the control of weeds in cotton has become an accepted production practice during the last ten years. In the process of becoming an established practice, this use of herbicides has created several new problems of a temporary nature and has been associated with stand losses in isolated cases.

The use of 2,4–dichlorophenoxyacetic acid (2, 4–D) for weed control in irrigated regions, especially on ditch banks, provides possibilities of contaminated irrigation water. A series of investigations has been conducted in the field to determine the response of certain crop plants to applications of 2,4–D in irrigation water, particularly at rates totaling herbicidal dosages. The first investigation dealt with Red Mexican beans and the results were published in 1954. This report deals with sugar beets, a root-type of crop plant.