Vegetable Growers' Handbook Chapter VIII: Weed Management

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Economic losses due to weeds are encountered nearly everywhere weeds occur. To better appreciate the losses due to weeds, consider the following results of weed infestation:
Lower Yields, Less Efficient Use of Land

  • Yields frequently are reduced by weeds competing with vegetables and other crops for water, nutrients, and light.
  • Crop choice may be limited by the presence of high populations of weeds. Most vegetable crops will not compete effectively against heavy weed growth.
  • Harvesting costs are commonly increased. Mechanical harvesting may be impossible.
  • Root and crop damage may result from cultivation designed to control weeds. Soil structure may be destroyed by repeated cultivation, especially if the soil is wet.

Added Costs from Losses Due to Insects and Diseases

  • Weeds may harbor insect and disease organisms that attack vegetables and other crops. For example: Carrot weevil and carrot rust fly may be harbored by the wild carrot, to later pose a problem for cultivated carrots. Aphids and cabbage root maggots may live in wild mustards to later attack cabbage, cauliflower, radish and turnips. Thrips thrive in ragweed and mustards, and may later attack vegetable crops. The virus diseases, squash leaf curl on watermelon and spotted wilt of tomatoes are carried by insect vectors that live on weeds in fields and along field borders.

Poor Quality Products

  • All types of vegetables and other crop products may be reduced in quality, rendering them less marketable. Weeds can cause vegetables to be spindly, poorly developed and colored "leafy crops;" root crops can become poorly formed; fruits (tomatoes, peppers, beans) undersized, low quality, and poorly shaped; and, foreign matter originating from weeds occurring in crop products are a few examples.

More Problems in Water Management

  • Weeds are becoming increasingly important in irrigation and drainage systems. Weeds also pose a problem by reducing the efficiency of water delivery and drainage systems.
  • Less Human Efficiency
  • Weed control involves a large portion of the effort required of a vegetable farmer to produce a crop. Weeds interfere with harvest operations making them less efficient. This effort and expense directly influences the cost of crop production and thus, the cost of food at the retail level.
Lynn Brandenberger
Frank J. Daniello
Texas AgriLife Extension Service