The present report marks the completion of a 24-month study. The early phases have been described in brief in a progress report (3). Data contained in the earlier report are included in the present discussion to make the entire experimental record available as a unit.

Seedling legumes are slow growing plants and poor competitors. During this period of slow growth, weeds have opportunity to outgrow them, and choke out or seriously damage the legume stand. Many of the important weeds are annual broad-leaved plants such as pigweed (Amaranthus retroflexus), lambs-quarters (Chenopodium album), mustards, and certain annual grasses such as the foxtails (Setaria spp.) and crabgrasses (Digitaria spp.). Perennial weeds, when present, are a serious problem, but this study was directed primarily at annuals. Since the advent of the combine, volunteer wheat and oats from shattered grain have also become a serious problem in summer legume seedings after small grain.

The distribution of 3 (p–chlorophenyl)–1,1–dimethyl urea (CMU) in the soil horizon is an important factor to consider in using the material since it is a soil active herbicide. It has been reported that the persistence and toxicity of CMU vary considerably with soil type, temperature, and moisture conditions.

Big sagebrush (Artemisia tridentata, Nutt.) is such an aggressive increaser that most of the formerly grassy ranges of the inter-mountain and northwest regions have long since acquired a sagebrush aspect. A suggestion as to the impact of this change upon grazing capacity is apparent from a three-year study in northern Nevada. An average reduction in yield by 20 native and exotic grasses and weeds of about 70 per cent was shown under limited competition with big sagebrush (12).

Halogeton glomeratus, a weed poisonous to animals, was first observed in the United States near Wells, Nevada, 1934–5. Dayton has given a detailed historical sketch concerning its European-Asiatic habitats and species. The ecology of halogeton has been discussed by Cook and Stoddard, Fenley and Tisdale and Zappettini. Very little is known in the English-speaking world about the present status of Halogeton glomeratus in Asia, where this species is reported to be endemic.

Investigations during the past 3 years have established sodium 2,4,5–trichlorophenoxyethyl sulfate, hereafter referred to as 2,4,5–TES, as a potential herbicide for control of weeds in tomatoes. The chemical has been succesfully applied just after the last cultivation. The material may be applied either as a basal-directed spray or an overall spray in tomatoes since it becomes phytotoxic only after contact with the soil. Its promise as a herbicide suggests the need for a critical evaluation of possible effects on quality of the fruit. Three measures of quality which may be affected include taste, chemical composition, and malformations such as cracking, blossom-end rot and seedlessness.

Weed control is one of the principal problems of turf grass management. With the discovery that 2,4–D would selectively kill many broad-leaved weeds their control in turf has been minimized. As has been indicated by Grigsby (9), the widespread usage of 2,4–D may be an important factor in increasing the importance of crabgrass (Digitaria spp.) as a turf weed.

As early as 1946, a limited study conducted in Oregon (5) showed big sagebrush (Artemisia tridentata Nutt.) to be susceptible to the sodium salt of 2,4–D. Cornelius and Graham (3) stated that big sagebrush was highly susceptible or hypersensitive to 2,4–D. Kissinger, Hull and Vaughn (7), reporting on experiments conducted at the Beaver Rim area near Lander, Wyoming, found that the isopropyl and amyl ester of 2,4,5–T consistently gave higher kills for a given amount of chemical. One pound acid equivalent (hereafter referred to as pounds acid) of 2,4,5–T usually gave somewhat higher kills than two pounds acid equivalent of 2,4–D.

Centipede grass (Eremochloa ophiuroides) is a major pest to pasture lands throughout northwest Florida. It is a low growing perennial which spreads by stolons. In appearance it is intermediate between carpet grass and Bermuda grass; it has shorter nodes than the latter and makes a dense mat of creeping stems and leaves. Although it is a pest to pastures it is very desirable as a lawn grass. The fact that it is adapted to a wide range of soils and fertility levels provided sufficient moisture is present, makes it ideal for this purpose. In pastures it is undesirable because of its low feed value, and its dense aggressive growth which tends to crowd out desirable plants.

With the introduction of new chemicals for weed control, a tremendous effort has been expended toward finding a chemical weed control method for soybeans. Some of this research has been reported in the Research Reports and Proceedings of the North Central Weed Control Conference from 1946 to date. Much of the effort has been devoted to pre-emergence treatments on soybeans because of the apparent sensitivity of soybeans to foliage sprays of the present day herbicides.

It has been shown that extracts of various weeds and crop plants inhibit germination and seedling growth (1, 4, 5, 7). In early experiments (7) it appeared that extracts of leafy spurge (Euphorbia esula) were particularly effective. For this reason it was of interest to more fully characterize the composition of leafy spurge. The present communication summarizes the results of qualitative paper chromatographic determinations for amino acids and sugars.

A number of investigators have tested 2,4–D (2,4–dichlorophenoxyacetic acid) for the control of weeds in asparagus. Several workers (1, 3, 4, 6) have suggested the use of 2,4–D at rates varying from one to three pounds acid equivalent per acre as a pre-emergence treatment after disking in the spring and again after disking at the end of the cutting season. Warren and Hernandez (5) applied 2,4–D at the rate of four pounds per acre on April 28 just after the asparagus bed was disked. The yield and appearance of the asparagus spears was not affected by the treatment. According to Ahlgren et al. (1), pre-emergence application of 2,4–D caused injury to the first emerging spears in some cases, but caused little permanent damage. These and other investigators found asparagus plants susceptible to foliage applications of 2,4–D and warned against spraying the fern.

The herbicide, 3–(p–chlorophenyl)–1,1–dimethylurea (CMU), first reported by Bucha and Todd (1), is finding increasing uses in the field of weed control. The mechanism of action of this compound, however, is as yet unknown. One of the early symptoms of CMU toxicity is a chlorosis (2) which develops in both monocotyledonous and dicotyledonous species. Muzik et al. (5) have shown that while CMU will inhibit root growth, the primary toxic action of this compound is on the aerial portion of the plant. Cooke (3) showed that CMU brought about a large decrease in the sugar content of plants and suggested that the mode of action was through an interference with photosynthesis.

In studies on the growth of weeds, especially in the seedling stage and also in plant taxonomy in general, the problem frequently arises of finding a precise and simple means of describing a leaf or a cotyledon. To overcome this problem, we are using a system which, for want of a better name, we call the Budd-Best system. Briefly it is a system of using three numbers and a descriptive term (Figure 1).