Cultural Methods of Noxious Weed Control in South Dakota

This outline has been prepared as a guide for field workers in weed control; for county, township, and neighborhood supervisors and for farmers cooperating in the program. The control measures presented here are based on the latest information available from weed control research and proven field applications. A choice of methods and procedures is presented that will fit practically all situations. It is assumed that local practices will be kept within the limits of recommendations outlined. Each of the eight weeds listed as noxious will be considered and recommendations for the use of intensive cultivation with various crops will be outlined for each weed. The choice of procedure to be adopted will depend on several factors, namely: (1) extent of infestation; (2) value and productivity of the land; (3) availability of material, equipment, and manpower; (4) adaptability of control practices, and (5) adaptability of crops. If chemicals are to be used, Experiment Station Circular No. 69 should be obtained. The recommendations given in that publication should be followed closely. Colored plates of the noxious weeds which show pictures and give characteristics of these weeds are also available. Copies of the Circular No. 69 or the colored plates can be obtained from the County Agent\u27s office or from the Bulletin Department at South Dakota State College, Brookings, South Dakota. Some cultural practices that are recommended for weed control involve long periods of intensive cultivation. Those that leave the soil barren during the winter are conducive to soil erosion. ln areas where this condition is a hazard the practice should be modified to conform with recommended soil conservation practices

Chemical Control of Weeds in South Dakota

There are now many chemicals on the market that have possibilities for use in a weed control program. Many of these chemicals are being tested and several can be used in controlling weeds. This bulletin explains the use and value of the more important chemicals. Recommendations are based on experimental results from cooperative tests in South Dakota and the results reported at the North Central Weed Control Conference. The tests in South Dakota include plots established throughout the state in 1945 and 1947, and at the Weed Research Farm at Scotland, which was begun in 1946

Weed Control Equipment

Clean seed, proper seedbed preparation, good crop rotations, and sound soil management practices are reliable measures to use in preventing weed infestations. Once weeds have become established, special cultivation practices and chemicals are generally required to eliminate them. This circular discusses the equipment most commonly used for cleaning seeds, cultivating, and applying chemicals

Perennial and Annual Weed Control in South Dakota

Clean seed, good crop rotations and sound soil management practices are means of preventing weeds from infesting the land. Once they become established, however, special practices are needed to eliminate them. These practices include the use of special cultivation, competitive crops and chemicals. One application of any one of the practices seldom eliminates all perennial weeds now present and never eradicates a weed. Even though the top growth is eliminated, new weeds come from the seeds in the soil. Some of these seeds remain viable for as long as 20 years and many years of diligent work are required to eradicate them. The major portion of this circular is devoted to a discussion of special cultural and chemical practices needed to eliminate weed infestations. The recommendations are based on results of research work done in South Dakota and on recommendations made by the North Central Weed Control Conference

Chemical Control of Weeds in South Dakota

There are now many chemicals on the market that have possibilities for use in weed control. This circular explains the use and value of the more important chemicals. Recommendations are based on experimental results from cooperative tests in South Dakota and from those reported at the North Central Weed Control Conference. The tests in South Dakota include 49 sets of plots established throughout the state from 1945 to 1950, work conducted at the Weed Research Farm at Scotland from 1946 to 1950, work conducted at Brookings from 1947 to 1951 and at a Weed Research Farm near Gary which was established in 1950

Chemical Control of Woody Plants

Many woody plants are problems in rangeland, along roadsides, under utility lines, and along irrigation and drainage ditches. It is often desirable to control these plants on rights-of-way, but it is advisable to study the situation before controlling them on rangeland. Chemicals used to control undesirable woody species may also kill desirable range £orbs and woody plants. One should be certain that the range forage will be improved before he does any large-scale spraying. It may be advisable to conduct a few small-area trials before the entire range is treated. To make spraying pay on rangeland it is desirable to follow good range management so that grasses will take over as the woody plants die out. Even though the grasses are present, they will not spread after the woody plants have been killed except under light grazing or no grazing conditions. Many of the grass plants should be allowed to produce seed. In South Dakota research has been limited to the use of chemicals for the control of buckbrush, sagebrush and poison ivy. Therefore, most of the information presented was obtained from the North Central Weed Control Conference and from states that have more woody plant problems than South Dakota. Most of the suggestions offered here have not been tried extensively in South Dakota, but they have proved to be satisfactory under similar conditions

Weed Control Research in South Dakota

Clean seed, proper seedbed preparation, good crop rotations, and sounds soil management practices are the most reliable procedures for the control of weeds. They will eliminate many annual weeds and prevent infestation by most perennial weeds. Chemicals have proved to be valuable supplements to these practices. However, too many people rely on 2,4-D and, at least partially, neglect the standard practices. Consequently, weeds resistant to 2,4-D are allowed to spread. Once weeds become established, special practices are needed to eliminate them. These practices include the use of special cultivation, competitive crops, and chemicals in addition to the old reliable methods already mentioned. One application of any one of the practices seldom eliminates all perennial weeds. Even though top growth is eliminated, new weeds come from the seeds in the soil. Some of these seeds remain viable for as long as 20 years and many years of diligent work are required to eliminate them. The major portion of this circular is devoted to a discussion of research results obtained in South Dakota and neighboring states. The discussion of special cultural and chemical practices in concerned primarily with the control and elimination of weed infestations. It does not dwell on practices needed to prevent reinfestation of areas on which weeds have been eliminated

Control and Elimination of Field Bindweed

Field bindweed (Convolvu.lus arvensis L.), sometimes called creeping jenny, is a deep-rooted perennial that spreads by underground parts and by seed. One seedling, when not competing with other plants, is able to produce in one season a root system that penetrates 4 feet deep and spreads out about 2 ½ feet in each direction. In three growing seasons, the roots may go down 18 to 20 feet and spread out to form a circle 17 or 18 feet in diameter. The yield of crops is normally reduced 30 to 50% by a bindweed infestation. Yield was reduced an average of 42% in eight South Dakota wheat fields and 33% in 12 South Dakota oats fields. In Kansas, barley yield was reduced 65% and sorghum yield 48%. Field bindweed emerges later in the spring than leafy spurge, Russian knapweed, or hoary cress and is less difficult to eliminate. It emerges about the same time as Canada thistle or perennial sow thistle. To control or eliminate field bindweed, use intensive cultivation, soil sterilant chemicals, certain competitive crops, selective herbicides, or combinations of these

Control and Elimination of Thistles

Canada thistle (Ci.rsium arvense L.) and perennial sowthistle (Sonchus arvensis L. or S. ulignosus Bieb.) are deep-rooted perennials that spread by underground parts and by seed. All species emerge later in the spring and are less difficult to control or eliminate than leafy spurge, hoary cress, or Russian knapweed. They emerge about the same time as field bindweed. Prevention of seed production is more important for thistles than for most perennial weeds. Wind currents carry the seeds great distances. Thistles reduce crop yields. The amount of reduction depends on how thick they are. Two plants of Canada thistle per square yard reduced wheat yields 18%, and 19 plants per square yard decreased yields 36%. A heavy infestation of sow thistle caused a 69% reduction of oat yields. To control or eliminate these thistles, use intensive cultivation, soil sterilant chemicals, certain competitive crops, selective herbicides, or several combinations of cultivation, crops, and chemicals

Weed Control in Field Crops

Clean, seed, proper seedbed preparation, good rotations, and sound soil management practices are prime requisites for controlling weeds in crops. They will eliminate many annual weeds and prevent infestation by most perennial weeds. Chemicals are valuable supplements to these practices. However, if we rely on 2,4-D or other chemicals, we at least partially neglect the standard practices. Consequently, weeds resistant to chemicals are allowed to spread. Once weeds become established, special practices are needed to eliminate them. These practices include the use of special cultivation, competitive crops, and chemicals in addition to the old reliable practices already mentioned. One application of any one method seldom eliminates all perennial weeds. Even though they are eliminated, new weeds come from seeds in the soil. Some of these seeds remain viable for as long as 20 years and many years of diligent work are required to eradicate them. Numerous tillage and chemical methods that will control weeds in crops are available. In fact, it is possible to eliminate some of the most persistent perennial noxious weeds while growing crops if the proper combination of crops, cultivation, and chemicals is used. For detailed information on the control or elimination of any of South Dakota\u27s noxious weeds, refer to the circular that discusses the specific weed. If chemicals are to be used in the weed program, it is important to remember that chemicals cause more damage to crops when applied at certain stages than at others. This is particularly true when rates of application required to control perennial weeds are used. If the most tolerant stage of the crop does not occur when the weeds are in the most susceptible stage of growth, there are two choices-risk injuring the crop to get good weed control or get poor weed control with less chance of injuring the crop. Good weed control usually pays off in the long run. The maximum rate of chemical application that can be used on crops without much risk of reducing the yield is discussed on the following pages. Many annual weeds are killed with lower rates; consequently, the rate of application will frequently be lower than the maximums mentioned. On the other hand, many perennials will require higher rates than the safe rates mentioned. As a result one may have to use a more tolerant crop or risk injuring the crop if he wishes to eliminate the weed