Cattails (Typha spp) are common and troublesome emergent aquatic weeds throughout the United States. They interfere with proper utilization and maintenance of irrigation and drainage canals. They further interfere with flow of water in channels where water velocity is low, and cause deposition of silt. In reservoirs, farm ponds, marshes, and lake margins, cattails waste large quantities of water, crowd out plants which produce food for wildlife and often interfere with fishing, boating, and other uses of these bodies of water.

Previous studies by Bruns and Rasmussen (1, 2) showed that the longevity of the seeds of certain noxious weeds may range from several months to 5 years or more when stored in fresh running water. In order to gain information of this nature on additional weed species, a third test was initiated on April 4, 1952. The results of this study are reported herein.

Although many studies have been made on the behavior of herbicides in soils, there is still insufficient information to make intelligent use of many herbicides. Certain theories on herbicidal behavior in soils are well established in some regions, but the applicability of such theories to other regions under different soil and environmental conditions is not always known.

Sorghum is second only to wheat in importance in dryland crop production in the Southern Great Plains. Sorghum is planted during the season when several common annual weeds normally emerge. Proper pre-planting cultivation will often reduce the seriousness of weed infestations, but many times the crop is invaded by weeds. Under such conditions chemical weed control is of value. These studies were initiated to determine the effect of 2,4–dichlorophenoxyacetic acid (2,4–D) on the yield of weed-free sorghum.

Sun (2) reported that pith cells in the hypocotyl of soybean (Glycine max (L.) Merr., variety Monroe) became meristematic and vascular strands developed in the pith after treatment with 2,4–dichlorophenoxyacetic acid (2,4–D). Later (3), he found a retardation in elongation of roots from treatment with 2,4–D. The pericycle produced a mass of dense meristematic tissue extending to the periphery of the root. Even non-conducting cells of the primary phloem of roots became meristematic.

The herbicides, 3–(p–chlorophenyl)–1,1–dimethylurea (monuron) and 3–(3,4–dichlorophenyl)–1,1–dimethylurea (diuron), have been widely accepted as selective soil applied herbicides; they are now used in a number of crops and under a wide range of soils and climatic conditions. Their extreme residual herbicidal activity contributes to their success as residual pre-emergence herbicides and as semipermanent soil sterilants.

Perennial weeds capable of vegetative reproduction comprise, as a group, some of our most serious weed problems. Eradication is difficult where new top growth can be produced repeatedly from underground buds. A time honored control method involves the cutting of all top growth with special tillage implements each time sufficient new growth has been produced. In this way food reserves in the root system of the weed are slowly depleted until all growth stops. Root systems of most creeping perennial weeds are supplied with numerous buds on either the crown, lateral roots or rhizomes. Removal of the top growth of such plants with either chemicals or tillage results in the activation of a small percentage of the available buds and new top growth is produced. The new growth thus produced tends to prevent further bud activation presumably through the maintenance of auxin levels unfavorable for growth of these buds. This phenomenon is often referred to as apical dominance. Food depletion of the root system would be faster if more buds could be stimulated to active growth prior to each cycle of top growth removal.

A relationship has been noted between environmental conditions, including soil characteristics, and the movement, persistence and activity of herbicides applied to the soil. Field studies have often given differing, and sometimes contradictory results, possibly because of different environments. Empirical studies cannot fully explain these differences.

Once it has been determined that the primary mode of action of a herbicide is dependent upon entry into the plant through its roots, it becomes important to know what factors will influence its movement in the soil. The findings of Ennis (3, 4) and Baldwin, Freed, and Fang (1) that certain cereals absorb carbamates by means of their roots rather than through their leaves stimulated experiments to study the effects of various soil factors upon the persistence and movement of carbamates in the soil. Blouch and Fults (2) found that the effect of various soil types on the effectiveness of pre-emergence applications of CIPC to several crops was much less than the effect of soil structure and high levels of organic matter. Data presented by Ogle and Warren (9) indicated that organic matter may have considerable effect on inhibiting the movement of CIPC in the soil. They also emphasized that the herbicidal behavior of a chemical in soil cannot be predicted from a study of one soil type, since there appears to be an interaction between soil type and movement of the herbicide. Smith and Ennis (12) reported similar results and also found that oil solutions of CIPC were less mobile than aqueous solutions.

Only a few reports have been published on the susceptibility of rabbitbrush (Chrysothamnus spp.) to chemical herbicides (1, 2, 5, 6, 7). From these publications the following conclusions may be made: (a) 2,4–D (2,4–dichlorophenoxyacetic acid) is more effective on rabbitbrush than 2,4,5–T (2,4,5–trichlorophenoxyacetic acid), (b) June applications are generally best, (c) rabbitbrush is more tolerant to growth regulators than big sagebrush (Artemisia tridentata), and (d) resprouting from the stem base is common.

In contrast to the great development of chlorophenoxyacetic acids as herbicides, the fluorophenoxyacetic acids have received very little attention in weed control work, chiefly because they were difficult to synthesize. In addition until recently, they were not widely available. Thompson et al. (5) listed 2–fluorophenoxyacetic and 2–methyl–4–fluorophenoxyacetic acids as plant growth inhibitors. Crane and Blondeau (1) reported 4–fluorophenoxyacetic acid to be as effective as 4–chlorophenoxyacetic acid for inducing parthenocarpy in figs. A 100 ppm spray gave 88% fruit set with no foliar damage. Edgerton and Hoffman (2) stated that the same compound was moderately effective in delaying leaf abscission on apple trees and produced a 2,4–D-type formative effect on treated shoots. Weintraub et al. (6) showed with a bean leaf-area repression test that some of the fluorophenoxyacetic acids have a very high formative activity comparable to that of the most active chlorophenoxyacetic acids.

The absorption and translocation of radioactive 2,4–D in bean plants has been studied by many workers (2, 4, 5, 7). The translocation of radioactive carbon from applied 2,4–D has been demonstrated to be more rapid in susceptible bean plants than in resistant plants such as corn and wheat seedlings (2, 3, 4). The difference in reaction of 2,4–D with plant constituents was further established between these two types of plants (3, 6). A compound designated as “unknown 1” was the major metabolic product formed in 2,4–D treated bean plants while “unknown 3” was found mainly in 2,4–D treated corn and wheat seedlings.

Monuron, 3–(p–chlorophenyl)–1,1–dimethylurea, is used extensively for weed control in asparagus. Growers apply approximately 1.5 lb/A of monuron in the spring before harvest begins, and the same amount in late June at the end of the harvest season. Each application usually controls weeds for 6 to 8 weeks. Since this chemical controls weeds for such a long period, growers are concerned as to whether, after continued use on the same soil for a period of years, this material might accumulate in the soil to the point where asparagus is injured, or the soil might be made unfit for crops which might follow asparagus. Therefore, a study was made of the persistence and penetration of monuron in soils of asparagus experiments where this chemical had been applied each year for a number of years.

The application of small samples of various weed seeds or seed mixtures to greenhouse flats for herbicidal studies is usually a manual operation. Various size flasks, beakers or test tubes are employed for the distribution of weed seeds to the soil surface of the flats. However, this method is time consuming and often results in uneven distribution of the seeds.

Increasing the forage yield of rangeland by controlling big sagebrush (Artemisia tridentata Nutt.) with fire, chemicals, or mechanical means has become a common procedure. The main problem confronting researchers has been the remarkable ability of sagebrush to re-establish itself after a control program. Fire and mechanical means of control have proved to be effective in killing established sagebrush. However, a heavy stand of young sagebrush often becomes re-established within a few years (3). Since the use of chemicals for sagebrush control has developed within the last decade, very little is known concerning the re-establishment of the plant in chemically controlled areas.

Field studies have been conducted at the Irrigation Experiment Station, Prosser, Washington, to determine the effects of 2,4–dichlorophenoxyacetic acid (2,4–D) in irrigation water on certain crop plants. The possibilities of contaminating irrigation water through the use of 2,4–D for weed control, particularly on ditchbanks, prompted these investigations. The response of Red Mexican beans and sugar beets to 2,4–D in irrgation water has been reported (1, 2). This publication deals with Concord grapes, a woody-type of crop plant.

It has been difficult to accept as conclusive the indications that butyl ester forms of 2,4–D are more effective in the control of big sagebrush (Artemisia tridentata) than are isopropyl ester forms (2, 3, 5). Such indications may have been due to the manner of formulating the materials, and to the additives contained, rather than to differences between the esters. Additional information is necessary to prevent bias in the choice among ester forms.

Weed control constitutes one of the principal costs of onion production on muck soils. It has been estimated that cultivating and weeding make up nearly 40 per cent of the total labor cost in growing onions (5). The major component of this weed control cost is the hand labor required to remove weeds which come up in the onion row. During the past several years, research to find selective weedicides for onions and thus reduce weeding labor costs has been extensive.

The National Highway Program, recently approved, represents the largest peacetime construction program in history. The 41,000 mile network of interstate highways will be built on an average 300 foot right of way and will place over one million acres of land along the pavement subject to landscaping and maintenance.

The design and use of a variable-dosage spraying machine for the experimental evaluation of herbicides has been reported by Pfeiffer et al. (1). This equipment sprays at constant volume while simultaneously diluting the spray mixture exponentially. The machine is composed of a series arrangement of diluent tank, concentrate tank, pump, and nozzles. The concentrate tank is equipped with a rapid mechanical agitator. The pump propels the spray liquid from the concentrate tank through the nozzles in the conventional manner. The liquid withdrawn from the concentrate tank is replaced by an equal volume of water or other diluent from the diluent tank. Thus the concentration of active ingredient in the spray decreases logarithmically with the volume of spray delivered. Since spray volume is constant with time, by moving the sprayer at constant speed, the rate of application of the active ingredient becomes a logarithmic function of distance along the plot. The machine is mounted on a four-wheel-drive light truck and draws power for the pump and agitator from the power take-off.