Various species of barberry serve as alternate hosts of the destructive stem rust disease of wheat, oats, barley and rye. Eradication of susceptible barberry plants is one of the principal control measures.

Most workers with herbicides agree that the effects brought about by many of these substances must be the results of altered enzymatic action within the plant. The actual mechanism is still a matter of conjecture in spite of some excellent research and well founded theorizing. A brief examination of enzymes and enzyme action in the light of results obtained with 2,4-D particularly, may suggest how this herbicide fits into the enzyme picture.

Before discussing the subject of “Trends in Teaching Weed Control”, let us consider the agricultural situation for a momentl According to agricultural statistics there is a trend towards larger farms. These can be operated most efficiently only by making economical use of equipment. It can also be said that farming is a business. Those operating farms are conscious of costs. Therefore, any weed control program that might be adopted would be favored principally because of its economic value. Farming is also becoming more scientific as we are now living in a scientific age. As farming becomes more scientific, those persons operating farms must have the ability to make use of new developments regardless of their own scientific tendencies.

To most people, the word weeds signifies pest plants of the farm, roadside, or other upland areas. However, weeds also occur on, under, or near water. Fifteen million dollars have been spent on a single aquatic nuisance in the South—the prolific water-hyacinth which clogs navigable streams and lakes with its growth. Hundreds of thousands of dollars have also been expended on control of the waterchestnut or water caltrop in the Potomac River. In addition, smaller-scale local campaigns are continuing against cattails, reeds, giant cutgrass, maidencane, alligatorweed, needlerush, lotus, rose-mallows, willows, alders, buttonbush, and similar weeds that interfere with land use for recreation, irrigation, or other purposes. Since control of marsh and aquatic plants in wildlife habitat is an unfamiliar activity to most weed workers, broad aspects of its what, why, and how will be explained briefly.

Brush species treated under field conditions have exhibited a variable response to growth-regulator type herbicides which cannot be explained by previous research findings. Light and temperature are known to influence the response of plants to these materials. Field observations have indicated that environmental factors such as relative humidity and soil moisture may also control to some degree the reaction of plants to herbicides. This chamber is being used to subject seedlings and small plants to controlled conditions of environment for evaluating the hypotheses suggested by field observations.

An understanding of the physiological and morphological responses of plant tissues to phytotoxic compounds makes possible a more intelligent approach to the problem of selecting and developing new herbicides for the control of weeds in growing crops. This area of investigation is frequently neglected in the haste to screen the many new chemicals which are reported.

In reviewing weed control literature, papers are frequently encountered in which the data have been presented without statistical evaluation. It is important for research workers in the herbicide field to be able to estimate the validity of their comparison just as it is for the workers engaged in fertilizer studies or any other phase of field research. Arithmetic means presented alone in a graph or in a table are extremely difficult to evaluate. Even though the author of a paper may have confidence in the significance of his data, it is difficult for the reader of a research report to evaluate the conclusions if an estimate of the experimental error is not presented. This may seem to place undue emphasis on statistical analysis itself. Yet in the relatively new field of weed control, few workers have had sufficient experience to judge the significance of differences of varying degree.

The Southern naiad, Najas guadalupensis (Spreng.) Morong. is a submersed water weed commonly infesting water control systems in south Florida, especially in the areas underlain by calcareous deposits where the canal waters are mineralized. Dense growths of this plant appear to have become more prevalent in recent years following the removal of water hyacinths by the use of 2,4-D.

To those engaged in testing chemical compounds for herbicidal properties a troublesome problem is familiar, namely, what species or small group of species can best represent the reaction of many plants to a compound the potential of which is unknown.

Since it was first discovered by Bucha and Todd, that 3-(p-chlorophenyl)-1, 1-dimethylurea would kill most plants if applied at dosages of 20 pounds and above per acre there has been much speculation as to whether it is translocated in plants. Observations from early field trials indicating that soil treatments with this compound were more effective than foliar applications led to the assumption that entrance of the herbicide into plants was primarily through the roots. Loustalot demonstrated positively, however, that this substituted urea is also absorbed through the leaves and stems. Recent investigations at this laboratory, contrasting essentially equal applications on foliage and roots of several species, have also indicated that appreciable injury is caused by foliar absorption of the compound.

As in many other states, weed control is a serious problem in North Dakota. To meet the situation a statewide control program has been developed over the years by the Extension Service with the Extension Service Agronomist in charge, As the weeds were still gaining ground special emphasis was placed in 1953 and 1954 on a statewide program for more effective weed control.

The control of weeds in strawberries is one of the most essential factors in strawberry production. Strawberry plants are easily overgrown by tall, rapidly growing weeds and, in a few weeks, they may be severely damaged. Hand hoeing to control weeds in strawberry plantings is a very expensive operation varying from $100 to $300 an acre, or even more depending upon the weed infestation. Growers have used various means of reducing weed competition, including the use of geese, the use of virgin land, lands relatively free of weeds, and fall planting for spring fruiting. In recent years, investigations have been conducted on the use of chemicals for weed control in strawberries.