Leafy spurge is a perennial weed that is found in almost every state north of the fortieth parallel and in the southern portions of most Canadian provinces. Heaviest infestations are found in Minnesota, the Dakotas and the Prairie Provinces.

Aslander was the first worker to report on the use of sodium chlorate as a herbicide; and Crafts and Raynor first reported on the use of borates as herbicides. They concluded that the herbicidal properties of any boron compound are related directly to the boron content of the compound. The fact that the borates tend to remain in the top layers of the soil while chlorates are easily leached, led them to propose that a mixture of the two would make an ideal soil sterilant.

Several triazines exhibit high phytotoxicity towards many species of higher plants and are being extensively studied as possible herbicides. Moreland et al. and Exer reported that 2-chloro-4,6-bis(ethylamino)-s-triazine, simazine, inhibited the photochemical activity of isolated chloroplasts. Exer also presented evidence that the inhibited reaction involved the photochemical reduction of DPN, diphosphopyridine-nucleotide. Gast has shown that in Coleus Blunei Benth. simazine blocked starch production in the light and that this effect was overcome by the addition of sucrose to starch-free leaves in the dark. These results indicated interference of photosynthetic CO2 fixation by simazine. Roth reported that simazine inhibited photosynthesis in Elodea but had a stimulating effect on respiration. In light of these findings a study of the effect of simazine and certain related triazines on the photosynthetic CO2 fixation of red kidney bean was undertaken.

An understanding of the physiological action of various herbicides is based in part upon a knowledge of the exact path of movement of the substance in the plant, the rapidity of transfer from one tissue to another, and the relative proportion of the total conductive tissue that is effective in transfer under any given set of conditions. Although the intercellular distribution of radioactive isotopes in both plant and animal tissues has been studied by the use of histoautoradiography, only one brief paper describes the use of this method with plant growth regulators.

Typha angustifolia L. var. brownii (Kunth) Kronf., known as cumbungi in Australia and narrow leaved cattail in the U. S. A., is a deep rooted perennial widely distributed throughout the world. It occurs naturally in swamps and marshy areas and also in irrigation channels, where it may seriously impede the flow of water during the irrigation season. Various mechanical methods of control have beeen devised; the most successful consists of regular cutting and subsequent maintenance of 15 to 18 inches of water above the cut stalks. This method was successfully employed in the Murrumbidgee Irrigation Area of New South Wales for many years, but recently has been virtually discarded because of rising labour costs.

Halogeton glomeratus was first discovered in the United States growing in the vicinity of Wells, Nevada, in 1934–35. Since that time it has invaded Utah, Nevada, Wyoming, Montana, Colorado, Idaho, Oregon, and California. The total area it infests now exceeds 11 million acres.

Hot water extracts of quackgrass (Agropyron repens (L.) Beauv.) rhizomes and leaves have been reported by Kommedahl et al. and Le Tourneau et al. to inhibit seed germination and growth of various crop plants. Experiments were performed to determine in which organs the toxic material is located, whether it is the same substance in all organs, and to compare toxin production in two clonal lines of quackgrass. In addition, experiments were performed to determine whether soil in which quackgrass had been growing was toxic and to determine if toxic material is present in young seedlings.

Davis and Duke in 1955 reported successful use of a 36 lb ahg solution of the propylene glycol butyl ether ester of 2,4,5-T applied by means of a tree injector. This tool is essentially a modification of the Cornell tool described by Cope and Spaeth in 1931, and subsequently tested with ammonium sulfamate and 2,4,5-T.

Good plot sprayers are essential in weed control investigations where chemicals are to be applied uniformly and in specified quantities. Derscheid described such a machine in 1952 and this machine, or similar models, have been used quite widely. The purpose of this paper is to report on a sprayer which was built as an improvement on Derscheid's machine. A number of these modified sprayers have been built at Swift Current and used successfully by other weed workers in Canada.

Practical and economical weed control measures are a necessary part of tree fruit and grape production. Weeds and grasses are serious competitors of fruit plants for moisture and nutrients; they provide cover for destructive mice, and interfere with harvest of the crop.

Witchweed (Striga asiatica) was first collected and identified in the United States during the late summer of 1956. This parasite attacks the roots of plants primarily in the family Gramineae. In the United States it appears to be a potential threat to the corn and grain sorghum crops. The seed of this annual germinates under very exacting conditions and can attach itself to a growing root tip of a host plant. Infestations build up, and spread is by seed which are produced in abundance. Beginning infestations may cause a few stunted crop plants while older infestations may cover several acres or entire fields and completely kill the host plants before they can produce a crop.

The Russian thistle (Salsola kali L. var. tenuifolia Tausch) called in some parts of México “saladilla” is an important weed in the dry regions of the United States. It was introduced in 1873 or 1874 to South Dakota and from there migrated to the West and Southwest, reaching California between 1892 and 1895, where it constitutes a serious problem.