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Weeds are important biotic constraint to food production. Weeds compete with crops for the same resources, basically water, nutrients, light and carbon dioxide. Furthermore, they are alternate hosts for crop pests and pathogens. Moreover, some of them lack autotrophy and fully develop only by parasitizing crops or wild hosts. Globalization of trade and weak legislations on weed control in most of the developing countries has favored spread of Invasive Alien Plants (IAP).

Weeds, in general, precede crops on farming lands and are major yield reducing factors. In ecological terms, most annual weeds are r-strategists, establishing populations with high relative growth rate (r). Thus, they produce numerous viable seeds and their populations quickly build up, in an exponential pattern. Weed competition with crops reduces agricultural output (quantity and quality), and increases external costs by spreading them across farm boundaries. It is also a major constraint to increased farmers’ productivity, particularly in developing countries where weed control claims 20 to 50 % of farmers’ time and keep smallholders in a vicious circle of poverty.

From FAO Integrated Weed Management


  1. Ralph Waldo Emerson described a weed as a plant whose virtue has not yet been discovered. And when you’re hoeing or pulling weeds, it definitely can be a challenge to find anything virtuous about them. Those that are the peskiest and most hated thrive in places you don’t want them to be, whether...
  2. TheNational Invasive Species Information Center (NISIC)was established in 2005 atUSDA'sNational Agricultural Library (NAL)to meet the information needs of users including theNational Invasive Species Council.Executive Order 13112established the Council in 1999. NISICmanages the...
  3. The Weed Science Society of America, a non-profit professional society, promotes research, education, and extension outreach activities related to weeds; provides science-based information to the public and policy makers; and fosters awareness of weeds and their impacts on managed and natural...
  4. The NPDN was established in 2002 in response to the need to enhance agricultural security through protecting health and productivity of plants in agricultural and natural ecosystems in the U.S. With support from the USDA-NIFA and through the collective efforts of many individuals representing...
  5. 2018-11-13 Mistletoes (parasitic shrubs from diverse families), dodders (species of Cuscuta); and witchweeds and their relatives, Striga, Alectra, and Rhamphicarpa species are major constraints on African crops especially in grain and legume production. They are highly specialized weeds so understanding...
  6. Ragweed parthenium (a.k.a. parthenium weed, Santa Maria feverfew, congress grass, carrot weed, white top, etc.), a member of the Asteraceae (Compositae) family, is native to Mexico and Central and South America and is becoming an increasingly troublesome weed around the world (Figure 1)....
  7. 2018-08-08 Session: African Witchweeds and Their Relatives—Biology, Sanitation, and Control Biographical Information: Lytton John Musselman is Mary Payne Hogan Distinguished Professor of Botany at Old Dominion University and has researched Striga as a Fulbright Professor at the University of Khartoum; as a...
  8. The quickest and safest way to learn foraging is with a local expert. You not only learn what there is to know but do not spend time learning things you don’t need to know. Further, you also get the local angle on plants, important information that is usually not found in foraging books published...
  9. Abstract,Outlook on Agriculture. 2017 In order to determine the critical period of weed control in sesame, field studies were conducted during the 2014 and 2015 growing seasons in Estahban, Iran. The experiments were conducted based on factorial arrangement which involved a randomized complete...
  10. Rating: 5.0 - 1 Vote
    2016-09-08 Material is presented in English and Kiswahili Parthenium hysterophorus is a noxious weed invading East Africa. It reduces crop growth and can harm the health of both humans and animals. ECHO is raising awareness of it through an educational video, presentations, and community involvement.
  11. 2017-02-15 Except: Parthenium hysterophorus, also known as carrot top, white top weed, and fever few is a fairly new invasive weed but has quickly become one of the worst weeds to tropical areas(CABI 2015). In Ethiopia it is known as Farmasissa which means “sign your land away” (IAPPS 2016). Originally from...
  12. 1985-04-01 On the small farm, or in the home garden, techniques suitable for the production of food might be quite different from those used in large-scale production systems. The use of machinery, for example, might be impossible or uneconomical, or special small-scale equipment might be needed. The wide...
  13. This article is from ECHO Asia Note #26 ECHO Asia Impact Center staff members first heard about alternative herbicide recipes that use fermented papaya and pineapple from a retired technical school teacher and organic farmer, Kru Pratoom. As weeding is a big part of any farmer’s life, the Seed...
  14. 2017-02-09 Parthenium hysterophorus, also known as carrot top, white top weed, and fever few is a fairly new invasive weed but has quickly become one of the worst weeds to tropical areas(CABI 2015). In Ethiopia it is known as Farmasissa which means “sign your land away” (IAPPS 2016). Originally from Central...
  15. 2015-03-26 Understanding the structure of plants and how they interact with their environment proves to be very important and helpful in overcoming agricultural challenges from drought to pests and from climate change to introducing new plant varieties. In this workshop, participants will gain valuable...
  16. How to get started in this thick mat of weedy trees? What to do about all the huge clumping grasses in the pineapple patch? How to manage this morning glory vine strangling the orchard? I have had a lot of questions come up in the course of working in permaculture in Hawai'i, for myself on my own...
  17. 1976-01-01
  18. Rating: 3.0 - 1 Vote
    2002-10-01 During one rainy season 24 families in a Mexican village and 10 vendors at a regional market were regularly interviewed about type and quantity of weed use. Also the weed vegetation was surveyed and 49 farmers were interviewed concerning their farming practices and costs. All of the 74 weed...
  19. 2017-01-20 Both in Ethiopia and in the countries of East Africa, the continuing proliferation and spread of invasive alien species (IAS) is now recognized as a serious problem, which needs to be addressed. While this situation has improved dramatically over the past 10 years, further progress has been...
  20. Rating: 5.0 - 1 Vote
    1998-10-01 Amazon.com Description People interested in tropical gardening or botany will find this an indispensable guide to several hundred species of plants with edible leaves. Leaves can provide high-quality food, and in the tropics, many are from perennials requiring little effort for their abundant...
  21. 2016-07-11 Recently, ECHO East Africa Regional Impact Center Director Erwin Kinsey and Technical Research Coordinator Bob Hargrave received a request from an ECHO network member to identify and propose control methods for a “new weed that is spreading and smothering trees and hedges.”
  22. Rating: 2.0 - 1 Vote
    2007-10-20 Overstory Issue 188 (about accelerated natural regeneration, or ANR) included information about weeding in forests. Here we share an excerpt on reducing competition with weeds.
  23. Rating: 4.0 - 1 Vote
    1997-07-19 Scientists at the International Centre for Research in Agroforestry (ICRAF) in Kenya have recently determined that the weedy shrubTithonia diversifoliahas potential as a green manure crop.
  24. Rating: 3.0 - 1 Vote
    2002-10-01 A habitat management system to control stemborers and striga has been developed by the International Centre of Insect Physiology and Ecology (ICIPE), along with Kenya’s Ministry of Agriculture, the Kenya Agricultural Research Institute (KARI), and IACR-Rothamsted of the UK. The system is called a...
  25. Rating: 3.0 - 1 Vote
    1996-01-19 The parasiticweed Striga hermonthica is a major problem in African millet fields. International Agricultural Development (Jan/Feb 1994) reports that dense intercropping of cowpea in millet stands can reduce Striga emergence.
  26. 1993-01-01 When I visited Jamaica a couple years ago I learned that farmers in south St. Elizabeth Parish were growing a good crop of scallions. What was unique is that they relied on rainfall in an area that is normally too dry for intensive vegetable production without irrigation. In fact, they were...
  27. 2017-02-09 Parthenium hysterophorus, also known as carrot top, white top weed, and fever few is a fairly new invasive weed but has quickly become one of the worst weeds to tropical areas(CABI 2015). In Ethiopia it is known as Farmasissa which means “sign your land away” (IAPPS 2016). Originally from Central...
  28. AccessAgriculture Training Video Farmers in Madagascar show how following four key principles can give you a good rice harvest despite the presence of striga. English French Kiswahili Malagasy Portuguese
  29. Weeds are important biotic constraint to food production. Weeds compete with crops for the same resources, basically water, nutrients, light and carbon dioxide. Furthermore, they are alternate hosts for crop pests and pathogens. Moreover, some of them lack autotrophy and fully develop only by...
  30. Abstract ,Crop Protection, 2015 Weeds are a hidden foe for crop plants, interfering with their functions and suppressing their growth and development. Yield losses of 34% are caused by weeds among the major crops, which are grown worldwide. These yield losses are higher than the losses caused by...
  31. An integrated approach to plant protection The mission of the International Association for the Plant Protection Sciences (IAPPS) is to promote and support an integrated, scientific approach to plant protection. Embracing a wide range of research approaches, technologies and practices, IAPPS aims...
  32. The Official Journal of theInternational Association for the Plant Protection Sciences The Editors ofCrop Protectionespecially welcome papers describing an interdisciplinary approach showing how differentcontrol strategiescan be integrated into practicalpest managementprograms, covering high and...
  33. AccessAgriculture Training Video The parasitic weed striga causes more damage to cereal crops in poor soils, so both problems have to be tackled together. In this video we will learn why it is important to combine at least three control methods to reduce striga and obtain a good yield of sorghum,...
  34. AccessAgriculture Training Video Effective weed control can increase yields by more than 50%. As a farmer it is therefore worthwhile taking a closer look. In this video you can learn how to control weeds most effectively. Ateso Chichewa English French Kiswahili Luganda Lugbara Luo Runyakitara
  35. AccessAgriculture Training Video Effective weed management can increase yields by more than 50%, but usually takes a lot of time. As a farmer it is therefore worthwhile investing in labour-saving weed management tools. In this video you can learn how to control weeds in lowland rice using the...
  36. AccessAgriculture Training Video One of the major parasites is striga, a weed that sucks the juice and nutrients from cereal crops such as millet, sorghum and maize and causes great yield losses. A single striga plant can produce hundreds of thousands of seeds. The seeds are so tiny that most...
  37. AccessAgriculture Training Video It is important to pull striga weeds with your hands before the time it produces seeds and spreads. As it is laborious, better reduce the number of striga plants by applying compost or manure, and by rotating or intercropping with non-cereal crops, such as cowpea....
  38. AccessAgriculture Training Video Compost is more powerful than manure. What is less known is that the micro-organisms in compost attack striga seeds in the soil. Compost also decreases the amount of striga that will sprout, and reduces its negative effect on cereal crops. Let us look at how...
  39. AccessAgriculture Training Video Farmers in northern Nigeria are changing the way they intercrop their sorghum and millet with cowpea. By planting both crops at higher densities and in separate rows, and by applying some organic and mineral fertilizer, they harvest more and reduce damage by the...

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