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.

Chess, Bromus secalinus L., and downy brome, Bromus tectorum L., are two of the more common and troublesome weedy grasses in the midwest and western states. Downy bromegrass is widely dispersed in Michigan in pastures, meadows, cultivated fields, and roadsides. Chess occurs frequently in grain fields, particularly in the southern part of the state. These two species have been variously described as annual, winter annual, and either annual or winter annual plants.

Amino triazole (3–amino–1,2,4–triazole) is a chemical which causes chlorosis in many plants. In many cases chlorosis is followed by the death of the plant. It is not known definitely whether the synthesis of chlorophyll is inhibited or whether chlorophyll is destroyed. Generally, only new growth, in which the pigment is being formed, shows chlorosis. This suggests that chlorophyll synthesis is affected. The chlorosis has been shown to be proportional to the amount of amino triazole applied. In order to establish a basis for further work, evidence on the translocation and fate of the chemical in several different plants is presented here.

Some data have already been presented on the kill of blue oak (Quercus douglasii H. & A.) with concentrates of 2,4–dichlorophenoxyacetic acid (2,4–D) and 2,4,5–trichlorophenoxyacetic acid (2,4,5–T) applied to cuts in the trunks. The present paper is concerned with reporting some similar studies on species which are noted for being persistent or vigorous sprouters. Since the sprouting question represented an important part of these studies, it was necessary to make observations for several years after treatment to arrive at some relatively dependable conclusion concerning effectiveness.

The discovery of the herbicidal properties of the phenoxyalkylcarboxylic acids created an impetus in research on the development of new herbicides. A number of these compounds are now being used commercially as pre-planting, pre-emergence, and post-emergence treatments for the control of dicotyledonous and monocotyledonous, annual and perennial weeds in a variety of weed-crop situations.

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.

The toxicity of the substituted urea herbicides may persist in the soil for considerable periods following treatment. Consequently, they have been used extensively as pre-emergence and post-emergence herbicides and as soil sterilants. In the drier regions of the western states injury to cereals may occur when they are seeded in the fall following cotton which has been treated with the substituted ureas to control weeds. Because of the nature of these compounds and because of their rapid acceptance as herbicides, much interest has developed in relation to their breakdown in the soil.

The influence of 3–amino–1,2,4–triazole (ATA) and eight of its salts or derivatives on defoliation and secondary growth in cotton, the straight growth and respiration of Avena sections, and the respiration of cotton leaf discs were reported in a previous paper.

Numerous workers have reported the presence of growth and germination inhibitors in various plants. In some cases the active principles have been isolated and characterized. It has been further found that some of these inhibitors have a role in the interaction of species. Thus, the compound, 3 acetyl–6–methoxybenzaldehyde, is leached from the leaves of Encelia farinosa and suppresses the establishment of other species in the immediate vicinity of the parent plant.

In 1949, Bruns and Rasmussen initiated studies to determine the length of time certain weed seeds would maintain viability when held in fresh running water. Seeds of white top, Russian knapweed, Canada thistle, morning glory, and poverty weed were placed in Lumite screen bags and submersed at 12- and 48-inch depths in the Prosser Power Canal.

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.

Studies with plant growth-regulators are severely handicapped unless methods are available for quantitative determinations of these chemicals. Beginning with the classical work of Went, several techniques have been developed to obtain a quantitative measure of plant growth-regulating chemicals. Brown and Weintraub, Hitchcock and Zimmerman and Frankton have discussed the use of biological assays as quantitative tests for various hormone-type chemicals. Thus far, the only biological methods developed beyond the semi-quantitative stage are those depending on cell elongation in shoots, inhibition or elongation of roots, and the stimulation of ovary development.

The increasing use of dalapon (sodium salt of 2,2–dichloropropionic acid) by farmers and agricultural workers has stimulated interest in its effect upon the soil microflora and soil microbiological processes. Thiegs and Holstun and Loomis concluded that dalapon is broken down by an undertermined fraction of the soil microbial population. Magee and Colmer reported that dalapon at rates higher than those used in field applications, was toxic, as measured by manometric methods, to certain species of Azotobacter. Smith, Dawson, and Wenzel reported the effects of several other herbicides on soil microorganisms under laboratory conditions.

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.

The application of 2,4–dichlorophenoxyacetic acid (2,4–D) in herbicidal concentrations to plants has resulted in a number of correlations with post-treatment physiological and biochemical changes. Whether these changes are of a secondary nature or actually involved in the basic mechanism of herbicidal action cannot always be determined at the present time. One such case is the influence of 2,4–D on the uptake of minerals from the soil. Wolf et al. demonstrated that the content of potassium was considerably lower and calcium was higher in leaves of 2,4–D treated plants than in controls, but when the analyses from the leaves were combined with those of the stems, these differences largely disappeared. They also noted that chlorine and sulfur were higher in treated plants than in controls, while phosphorus was lower in treated plants than in controls. Fang and Butts showed that the amount of phosphorus in the leaves from 2,4–D treated plants was much less than that found in the leaves of control plants, while the amount in either the stem or root from these two groups of plants showed no significant differences. These results have been confirmed by Rebstock et al. who have shown that the total amount of phosphorus in treated plants was lower than that in the control plants, while at the same time the total phosphorus content of the stem tissue from 2,4–D treated plants was higher than that of the non-treated plants. The phosphorus content of the roots was not appreciably changed from that of the non-treated plants. Rhodes et al. noted that treatment with 2–methyl–4–chlorophenoxyacetic acid (MCPA) greatly lowered the potassium content of tomato and rape plants and suggested that the possible mechanism of MCPA action might be by interference with potassium metabolism. However, in a later publication Rhodes reported no effect of MCPA on the uptake of potassium, calcium or magnesium. With the possibility existing that 2,4–D exerts its action through interference with potassium or phosphorus metabolism, the present study was undertaken to examine more closely the influence of 2,4–D on mineral uptake from the soil.

The granular herbicide distributor described here was devised to satisfy the need for equipment that would spread the clay type of granular carrier with a high degree of accuracy in small plot field trials. Performance data and construction details are presented for the benefit of others doing research on granular herbicides.

The rate of disappearance of a herbicide from soil is one of the key properties in determining its utility. In some cases it is desirable that a selected herbicidal concentration be maintained in the soil as long as possible. In other cases, rapid dissipation is desirable after a given effect has been produced. Leaching is a primary factor in the removal of many herbicides from soil.