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Agronomic Crops > Crops Blog > Posts > Weeds: They are important to everyone! Here is why

No matter where I go, whenever a conversation strikes up between someone and myself and they ask what my occupation is and I say that I am a weed scientist, I get the same answer: "I surely could use your help!" I have found that whether I am in California, Alaska, Alabama, Texas, Pennsylvania, or overseas, everyone has an interest in controlling weeds. But I've often wondered, especially with all of the media interest in GMO's and environmental stewardship with pesticides, does the general public really know the impact that weeds have on everyday life for not only our food and fiber production, but also our water resources, recreation, schools, and public areas?  Most of the people that I encounter think of their lawns when they have a general question after finding out my occupation but weeds and their impact reach much farther than landscaping and making yards more beautiful. This article will detail the impact that weeds have on the different aspects of world in which we live and why weed management is so important not only aesthetically and for better yields but also economically to growers and the general public.

What is the impact of weeds?

  • They compete for light, water, and nutrients with the cultivated crop plants. Normally they are better competitors because they are better adapted to the environment, particularly if they are indigenous to the area, thus causing reduced crop productivity.
  • They harbor pests such as insects, disease, and pathogens making them available to invade the crop plants. This results in higher costs of insect and disease control which increases production costs.
  • They increase crop production costs. In order to increase yields by reducing competition, weeds must be controlled by hand weeding, herbicides, planting cover crops, tillage, etc. which increases the cost to produce the crop
  • Weeds interfere with harvesting and the seed being harvested becomes contaminated with weed seed. Some weed seed is very small and cannot be separated by the thresher during harvesting. When this occurs, the seed quality is reduced and they get a lower market value for the crop seed. This results in poorer quality products. Livestock may be priced lower or unmarketable because of weeds; for example, wild onion, wild garlic, or bitterweed flavor in milk; common cocklebur in wool, reduce the quality of the products. Poisonous plants may kill livestock, slow their growth rate, or cause many other abnormalties.
  •  Some weed seed is poisonous or injurious to livestock and humans. Livestock consume poisonous plants each year leading to numerous health problems including death. In the fall when common ragweed is in full bloom, humans have allergies costing millions of dollars in trying to control the symptoms and loss of work, in addition to those plants like poison ivy which if highly allergic can cause extreme discomfort and doctor visits
  • Weeds reduce the aesthetic value of areas such as public parks, golf courses, school grounds, in addition to lawns, common areas in high-dollar neighborhoods
  • Water management problems can be caused by a lack of weed management. Aquatic weeds can sometimes be a blessing for fishing but they can also get wrapped around the propeller of fishing boats, the weeds can be major problems for irrigation and drainage systems, lakes, harbors, and reservoirs.  They can restrict the flow of water and emit undesirable flavors in the water used by domestic water systems. Weeds around ponds, swimming pools, canals, and other water bodies cause an abundance of mosquitoes. Mosquitoes not only affect humans but animals as well and are very expensive and difficult to control in large areas.
  • They lower plant and animal yields. Weed control is expensive and directly affects the price of food production thus affecting the price of food and other agricultural products. Yet, without these control methods, food and other products would be less available, driving the prices even higher. As stated previously, weeds primarily compete for water, nutrients, and sunlight thus reducing yields but some weeds may also reduce yields by releasing their allelopathic compounds. Allelopathy is the process by which one plant species affects other plant species through biologically active substances that reduce the growth or inhibit the growth of another plant. Livestock yields are reduced due to less forage growth in pastures or hayfields or by poisonous plants that cause slower growth, biological problems in the livestock, or death.
  • Less efficient land use is an issue with weeds because the land is not used to its maximum capacity. 
  • Lower human efficiency is associated with weed management. Much of the world uses human hand-weeding and pulling for their weed control. In the U.S. most of the human labor is in the fruit and vegetable production systems however in Africa, India, China, and many other countries, human labor is what they depend on to weed their crops. The U.S. could never feed the world if we had to harvest our corn, soybeans, cotton, wheat, and rice by hand labor.
  • Human safety is affected by weeds. How many times have you been at a stop sign and you couldn't see the intersection well because of protruding weeds? When weeds are allowed to grow up on intersections they become safety hazards for the general public. The road crews do an excellent job trying to control these situations but they are often times on private land and it is a prized bush or tree that they refuse to have cut down.
  • As you see from the list above, weeds can affect virtually every aspect of everyone's life. Next, we will look at the economic impact that they have and why it is so important to our bank accounts that growers do their best to control these unwanted pests.

Economic Impact of Weeds

In Crops

In a study conducted at Kansas State University from 2007-2013, researchers studies the impact that leaving weeds uncontrolled would have in Canada and the U.S. given the improved genetics and fertility. They concluded that on an annual basis that the potential loss in value for corn is $27 billion and for soybeans is $16 billion based on their data. Overall average %% yield loss with no weed control in corn is 52% and soybean is 49.5%. 

It should be noted that crop yield losses caused by weeds (about 32%) are higher than those caused by either pests (18%) or pathogens (15%) (Oerke & Dehne, 2004)

Please see the table for more information.

Joyce A. Tredaway 

Department of Crop, Soil, and Environmental Science








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