The new scientific discipline, weed control, is the product of research. So long as man has grown crops for his own personal use, he has fought weeds, for nature favors community life for her plants. True there are examples of pure cultures of plants in nature; the white pine forests of the northwest, the buffalo grass prairies, wild rice in the northern lakes. But by and large, the areas now devoted to our major crops, wheat, corn, cotton and forage, were occupied by mixed plant populations and now they are in monoculture or in controlled plant populations and this nature abhors. Hence through the ages and even more today the farmer has been at war with weeds, the invaders of his crops.

Shortly after 1934 when Kögl and co-workers found that indole–3–acetic acid is a substance which has cell elongation activity in plants, many attempts were made to find other chemicals showing an indole–acetic–acid-like activity. It is 25 years now since Zimmermann and Wilcoxon found that naphthyl–1–acetic acid and some other aryl-acetic acids are active plant regulating compounds also. With these experiments it could be shown that the indole-nucleus is not essential for a plant growth regulator. The findings of Irvine showed that 2-naphthoxy-acetic acid is equally active as a phytohormone. This indicates that the acetic acid has not necessarily to be linked to the naphthalene ring directly. Thenaphthoxy-acetic acid was further modified chemically and became the starting point for the most widely used phytohormones: 2,4-D, MCPA and 2,4,5-T.

It is indeed a real pleasure for me to have the opportunity to participate in this third meeting of the Weeds Journal of Weed Society of America. The years I spent in the Weed Investigations Section were among the most rewarding of my professional life.

It is a great privilege and a pleasure to have this opportunity of discussing with you the status and organisation of research and development work on weed control in Great Britain. We have followed with keen interest the formation and growth of your “Weeds Journal of Weed Society of America” and have greatly enjoyed papers from your secretary, Dr. Warren Shaw, and your past president, Dr. Bob Beatty, at our own British Weed Control Conferences. Your immediate President is an especial friend of ours and it was while he was working with us in Oxford two years ago that he received intimation of his election to this post.

It gives me a great deal of pleasure to have been asked to talk on the subject, “A Conference Was Born”. Before going into the birth of the first conference I would like to give some history which had much to do with the first weed control conference.

Witchweed (Striga asiatica), a parasitic plant with brilliant-red flowers and hairy bright-green stems and leaves, was identified in the Western Hemisphere for the first time in 1956, although it had been present in the United States for several years. Figure 1 shows severe corn damage caused by witchweed. In a 1959 survey conducted by the United States Department of Agriculture witchweed was found on approximately 250,000 acres of land in 15 counties in North Carolina and 7 counties in South Carolina. It attacks many species in the family Gramineae. Witchweed jeopardizes the production of corn, sorghum, sugarcane, and probably other gramineous crops in any climatological regions of the United States where it may be adapted. This study attempted to obtain some indication of the possible limits of its spread.

Arsenic-containing compounds have been widely used in the field of weed control. Sodium arsenite has been employed for general contact weed control, and as a herbicide on turf areas. In the latter capacity it is used to control undesirable species without inflicting severe or permanent injury to desirable turf grasses. Disodium methylarsonate (DMA) and dimethylarsinic acid (cacodylic acid) have more recently been shown to possess herbicidal properties. DMA has been used for the selective control of crabgrass in turf, and for removal of certain weedy species from Bermudagrass.

The potential extensive use of certain new herbicides has made it desirable to study their effects on soil microorganisms. If these compounds have any retarding or stimulating influences on the general soil microflora, this could be reflected in carbon dioxide evolution during soil respiration experiments. Microorganisms are important to soil fertility because they transform potential plant nutrients into active or available forms, and carbon dioxide is a significant index of their activity. The effects on carbon dioxide evolution of four new herbicides that have shown promising results in field trials at this station are presented in this report.

One of the major characteristics limiting the usefulness of pre-emergence herbicide applications concerns the persistence of chemical activity in the soil. In many instances, the herbicides break down too quickly to obtain satisfactory weed control. On the other hand, there is the possible hazard that a chemical may be too persistent and thus endanger the growth of succeeding crops. Another closely related factor is susceptibility to leaching. It is especially important when chemicals are used that are toxic to the crop plants as well as the weeds.

Annual weeds have always been a problem to the cranberry grower, but certain changes taking place in the bog environment have caused an increase in the population of annual weeds in some areas in recent years. The decline of soil acidity as a result of the long term use of alkaline water for frost flooding, coupled with the well drained bog culture recommended for Wisconsin growers, have produced an environment to which certain annual weeds are adapted. With some species, particularly common ragweed (Ambrosia artemisiifolia), the extensive use of petroleum products as herbicides has encouraged the invasion of annual weeds following the suppression of oil sensitive perennials.

The literature does not reveal any direct information concerning the time of exposure or concentration required of a soil fumigant to kill weed seeds. For specific soils and conditions the appropriate rate of application may be known but this does not represent an actual toxic concentration. This is due to the fact that the toxicity of the fumigant may be decreased due to adsorption of the fumigant by the soil or solution in the soil water. This investigation was carried out to determine what concentration of fumigant is needed for a specific time to produce a given percent control of dormant imbibed seeds.

In 1950 an experiment was initiated at Mississippi State University to evaluate the comparative efficiency of certain promising herbicides in controlling weeds in cotton. The use of herbicides for weed control in cotton was beginning to be accepted as an agricultural practice. Results from a long-time experiment involving the use of herbicides for weed control in cotton were needed.

Blue oak (Quercus douglasii) is a common tree on several million acres of grazing land in California. It may occur as pure stands, but other species of woody plants, especially poison oak (Rhus diversiloba), are commonly associated with it. Leonard and Harvey, et al. reported the effectiveness of the cut-surface method using 2,4–D amine for killing blue oak. Unfortunately, killing of the blue oak results in a “release” of some of the under-story shrubs, which may become a problem later. A broadcast spray that will control all the woody plants is needed.

Quackgrass, Agropyron repens, is the major weed problem on at least half of the acreage planted to potatoes in Michigan. The northern counties of the lower peninsula and much of the upper peninsula have an ideal climate for quackgrass, and potato growers must include control measures in their production plans. The work reported in this paper was directed toward development of an effective and economical control program.

Foxtail barley (Hordeum jubatum L.) is a native, short-lived perennial bunch grass with a wide distribution in the United States. Hay containing the mature spikes can cause severe injury or death to animals fed upon it because of the barbed awns, which work their way into the face and mouth, opening the way for infections.

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.

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.

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.

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.