Considerable concern and confusion exists regarding the problem presented by the present occurrence and potential spread of halogeton (Halogeton glomeratus) (M. Beib) (C. A. May) in the United States. It is now 18 years since this weed was first found near Wells, Nevada. Since that time the plant has been reported from a broad region extending from Lassen county, California to the southern edge of Montana.

Galston and Baker have established that riboflavin is a photoreceptor in the destruction of auxin by visible light by in vivo and in vitro experiments. Carrol showed that riboflavin also reduced the activity of 2,4–dichlorophenoxyacetic acid (2,4–D). He believed that the reduction in activity occurred only in the presence of living plant material. The present studies using corn seedlings confirm the reduction in 2,4–D toxicity by riboflavin when the seedlings and substrate were illuminated. In addition, the inactivation of 2,4–D by riboflavin by light in vitro was also shown.

One of the important steps in the maturing of a field of science is the establishment of a journal devoted to that field. A centralized means of publication is almost a necessity if a given branch of knowledge is to progress. “Weeds” is an attempt to fulfill that requirement for the science and art of weed control. If need is a measure of probable success, the success of “Weeds” is assured. Weed control literature has been published in every kind of journal — agronomic, horticultural, engineering, chemical, botanical, — and farm papers of all types, to make only a beginning.

Since 2,4–D became recognized as a weed killer, thousands of experimental plots have been sprayed with this and numerous other chemicals. The various weed conferences have prescribed uniform experiments with uniform rates and dates of application, but there has been no uniform method of application. In order to apply the minute quantities of chemicals needed on small plots, it is absolutely essential that a constant pressure and speed be maintained and that uniform coverage of the entire plot be obtained.

The pre-emergence use of herbicides offers a means of controlling weeds during the extremely critical period immediately following planting. Weeds can usually be controlled by cultivation if the crop makes a few weeks’ growth before weeds emerge. However, it is practically impossible to mechanically control weeds which emerge ahead of or with the crop.

The weedy annual and perennial members of Euphorbia are widespread in the United States, occurring in every state. In at least nineteen states E. esula is considered serious enough to be declared noxious by law (PMA, 1946). In other states, to date, the members of this group occupy the position of a minor nuisance, to be controlled in the general clean-up of other weeds. E. corollata is noxious in Idaho and Wyoming; E. lucida in Idaho and South Dakota.

Generally, 2,4–Dichlorophenoxyacetic acid (2,4–D) has performed well as a selective herbicide for sweet corn. Sometimes, however, applications of 2,4–D presumably at recommended dosages have resulted in abnormal plant behavior. In certain instances reduced yields have resulted.

A successful weed control program, whether it be Federal, State or County is involved with research, education and regulation.

Had laws been enacted and properly enforced in all states thirty or forty years ago to prohibit the introduction of noxious weeds the weed problems of today would not be so serious.

The research worker who attempts the application of herbicides to a small area in such a way as to simulate general practice, is faced with a unique problem. The ultimate objective is to apply the chemical to as small an area as is feasible but in such a way that it will correctly represent what the activity on both weeds and crop plants would have been had the application been made on an acreage basis. Small plots are desirable if land or labor are limited, if expensive crops in farmers’ fields are being used, and particularly when the chemicals may be highly toxic, or the activity is unknown.

A high degree of control of annual weeds in cotton by the pre-emergence application of dinitro-secondary-butyl-phenol or its salts has led to appreciable commercial interest. Leonard, et al. showed that the above chemical was promising for controlling annual weeds in cotton, when applied to the soil as a pre-emergence herbicide, and there have been many reports on the method since that time. It was recognized that this treatment did not control perennial weeds such as nutgrass and Johnson grass, and that some additional treatment would be required to control these weeds. In January 1948, one of the authors had the opportunity to see sugarcane weeds in Puerto Rico controlled by the post-emergence application of fortified oil emulsions, and the procedure was included for study in the 1948 cotton tests. The primary interest of the authors was to find a spray that would control the perennial weeds and which, at the same time, would not be injurious to cotton. It was felt that the annual weeds could be controlled rather well by the pre-emergence treatment. The effect of fortified oils and oil emulsions and unfortified oils on cotton hypocotyls and on grass shoots showed that the fortifying chemicals (dinitro-secondary-butyl-phenol and pentachlorophenol) were quite injurious to cotton hypocotyls, but that some unfortified oils showed considerable promise for selectively weeding cotton.

Quackgrass (Agropyron repens) is a weed of major importance in the northern regions of the United States where cool, humid climatic conditions prevail. In the areas of Wisconsin having a heavy red clay soil, the weed is especially troublesome for the soil characteristics hinder the most effective use of cultural control measures. The fact that quackgrass can be found on the majority of the farms in northern Wisconsin is evidence that effective methods of quackgrass control are not being used. The question arises of whether generally recommended methods of quackgrass control are effective under the conditions prevalent in this area. The present study describes the results obtained during 1947 and 1948 at the Ashland Branch Experiment Station using several combinations of tillage, cropping and fertilization. An attempt was also made to compare the value of two methods of estimating quackgrass infestations.

The control of roadside weeds and brush has always been a major problem of roadside construction and maintenance engineers. People charged with the responsibility of keeping our highways, county, trunk and local roads free of weeds and brush have heretofore found the control of unsightly weeds and brush a major and laborious problem and expense. For the control of many annuals such as hemp, giant ragweed, small ragweed, daisy fleabane, etc., a very thorough, systematic mowing program, coupled with the establishment of a heavy grass cover has in many instances sufficed to keep weed growth down to a minimum. However, for the control of such roadside weeds as Canada thistle, perennial sow thistle, poison ivy, etc., as well as for the control of all types of brushy growth, the mere mowing and laborious cutting of such plants has not resulted in eradication. The mowing of perennial weeds and brush is like “picking apples off a tree” — such picking does not kill the tree. Furthermore, programs of control involving brush have had to be repeated every two or three years at terrific expense to the tax payer. Laborious mowing and hand cutting is followed quickly by regrowth, which in a year or so is as bad or worse as the original stand which was removed.

Millions of acres in the United States are being chemically treated each year for the control of weeds. Weed investigators have generally accepted the fact that certain herbicides affect certain plants to a greater degree than others. Because of this, numerous chemicals are being used. Except for 2,4-D, there has been little work done on the bactericidal and bacteriostatic properties of the recent herbicidal compounds. It is the purpose of this paper to report a study of the influence that several recommended and experimental herbicides have on the microbial activity of the soil population and to establish the usefulness of a simple procedure outlined by Nelson in making preliminary determinations of this type.

The employment of selective herbicidal sprays to kill or inhibit one or more undesirable plant species growing in close association with desirable species has become a common practice in producing certain crop and pasture species. Many crop and weed plants which are equally inhibited if exposed to certain herbicides during the germination period may show marked differential response when the tops of the same plants are sprayed with the materials. For example, the common small grains and corn are readily inhibited by the herbicide 2,4–dichlorophenoxyacetic acid (2,4–D) if exposed to solutions of the herbicide at the germination stage. Notwithstanding, 2,4–D is widely used in spraying these crop plants at certain stages to control weeds without causing significant damage to the crops. The lack of serious damage to these species from applications of 2,4–D to their tops may be attributed to several factors. Firstly, the spray may be repelled and shed harmlessly to the soil by the crop species and retained by the weedy ones. Secondly, the spray may be retained about equally well by the foliage of all species, but absorption and translocation of the herbicide to susceptible tissues, such as the stem and root apical meristems, may be less efficient in the non-susceptible species than in the susceptible ones. Possible differential accumulation of herbicides at the site of toxic action by susceptible and tolerant plants also may be important. Thirdly, the differential response of plant species to certain herbicidal sprays may be attributable to an inherent physiological capacity of the non-susceptible plant to tolerate the herbicide even in intimate association with the cellular components. Fourthly, some herbicidal materials appear to be readily taken up by the normal absorbing organ, the roots, of plants, but are not absorbed efficiently by the aerial plant parts because of certain physio-chemical relationships and internal morphological barriers. Fifthly, the position of the stem growing point may be a factor influencing the differential response of plants to herbicidal sprays. The apical bud of the stem in most broadleaf plants is usually wet by foliage sprays, whereas the stem bud of grasses is protected by several enveloping leaves. Sixthly, some species may inactivate the herbicide more rapidly than others and hence are not highly responsive.

With the advent of herbicides, a new tool has been made available for studying the effect of soil physical properties on crop growth. This new tool may be used for solving such problems as “What are the beneficial effects, if any, accruing from cultivation for the control of weeds?” “Is cultivation necessary for maximum production?”

The discovery of the herbicidal properties of 2,4–dichlorophenoxyacetic acid (2, 4–D) created a great impetus in the search for new herbicides. As the herbicidal properties of 2,4–D became more generally known, it was obvious that many closely related chemicals and other organic compounds should be evaluated for their herbicidal properties.