Weeds of farm crops

Abstract Weeds are plants that are growing where they are not wanted. Weeds can significantly affect crop yields by shading and smothering the crop as well as by competing for plant nutrients and water. This chapter outlines the identification and biology of some of the more important grass and broad-leaved weed species. Methods of control as well as issues with herbicide resistance are discussed. 

Key words weed biology, weed identification, methods of weed control, herbicide resistance. 

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Insect pests of farm crops are difficult to control when necessary activities such as tillage weeding irrigation and harvesting increase the pest population and decrease the numbers of its natural enemies. 

Weeds cause significant crop loss by direct competition for moisture, nutrients and light. In addition, they often harbour pests and diseases that can invade the crop, they may be poisonous and their seeds may reduce the quality of the grain or, if sown with the harvested seed, cause weeds to spread around the farm or between farms. In many cases, the presence of weeds in a crop at harvest will reduce the efficiency of the harvester and, thereby, increase the costs to the grower. 

Gruber, H., Handel, K. and Broschewitz, B. 2000. Influence of farming system on weeds in thresh crops of a six-year crop rotation. Zeitschrift fiir Pflanzenkrankheiten und Pflanzenschutz. Special Issue S7 33-40. 

Historically, tillage and hand weeding were the main methods of weed control. Since the advent of herbicide use in 1950, essentially all sugarcane in Australia now receives one or more herbicide applications. Virtually all of the crop is produced on family-operated, commercial-scale farms and is processed at cooperative or privately owned mills. 

Weed management in fruit, nut, and vine crops is an integral part of farm management. Each grower must manage vegetation around the crop plants to optimize growth and development of the crop and to obtain an economic yield. 

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