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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. Key Resource
    2019-03-21 This Technical Note provides an overview of parasitic plants of agricultural significance in Africa. Parasitic weeds cause drought stress and stunted crops. Affected plants include cereal grains (e.g., sorghum [Sorghum bicolor] and maize [Zea mays]) and grain legumes (e.g., cowpea [Vigna...
  2. 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...
  3. 2007-05-25 Weeds are the pioneer plants of disturbed soils and can adversely affect the use, economic value, and aesthetic aspect of the lands and waters they infest. Knowledge of the major mechanisms of weed survival is essential for developing effective methods of weed control to maximize the use and...
  4. 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...
  5. 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)....
  6. 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...
  7. 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...
  8. Abstract,Journal of Agricultural Science, 2019 The productivity of citrus plants has not reached its maximum potential due to the action of several factors that directly affect agricultural profitability. Among these factors, weed interference has a great importance since it causes a reduction in...
  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. 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. 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...
  12. 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...
  13. 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...
  14. 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...
  15. Key Resource 1976-01-01 Perspectives for developing countries for controlling aquatic weeds and using them to best advantage, especially those methods that show promise for less-developed countries. ASIN:B001988YC8
  16. 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...
  17. Key Resource 1998-10-01 Third Edition [library also has 2 copies of the 1975edition] 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...
  18. 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.”
  19. 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.
  20. 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.
  21. 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...
  22. 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...
  23. 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...
  24. 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...
  25. 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...
  26. Access Agriculture 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...
  27. Access Agriculture 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. Available languages Arabic Ateso Bangla Burmese Chichewa / Nyanja English...
  28. Access Agriculture 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...
  29. Access Agriculture 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...
  30. Access Agriculture 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...
  31. 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...
  32. 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...
  33. The parasitic weedC. campestrisis native to North America but has been introduced around the world and become a weed in many countries. It is by far the most important of the dodders, perhaps because of its wide host range. This ensures that there is a wide range of crop seeds that may be...
  34. 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...
  35. This review reports what has been done by whom. It imcludes articles directly related to weed-crop competition published prior to June 1978.
  36. 1994-01-01 Because managing weeds usually involves a combination of chemical and cultural methods, it should be based on a knowledge of the specific weeds to be controlled, the habitats in which thye are likely to occur and the means by which they enter and persist in a turfgrass community. This information...
  37. 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...
  38. 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...
  39. 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.
  40. 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...
  41. Access Agriculture 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...
  42. Access Agriculture 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...
  43. Available on: iOS Android When crop pests and diseases occur farmers want immediate solutions. Time is of the essence. If they have to go searching for information which takes days to find, it might already be too late. They need to know what the problem is, what's caused it, and what to do...
  44. 1985-01-01 The purpose of this book is to meet the need for a reference that relates the principles of weed science directly to weed control situations encountered in the field. Although the concept is simple, the objective is difficult to attain. To be successful in weed control, one must conceptualize...
  45. 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...
  46. This manual has several purposes. First, the extent and nature of weed problems are studied. Then, the importance of knowing the growth habits of the weeds is discussed. Next the various methods of control are examined. The recommended safety practices are also included in the study. Finally, the...
  47. 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...
  48. The descriptions of the 90 weeds included in this publication are arranged in the order of the appearance of the weeds in the taxonomic key. Common and scientific names of the weeds are those indicated in the Composite List of Weeds published by the Weed Science Society of America.
  49. 2004-01-01 Pgs 208: illus Gift of Wand Krolikowski March, 2023 The weeds shown in this book are arranged alphabetically by family and scientific name within famiy. For each species, the Weed Science Society of America approved family, common and scientific name is shown along with a picture. Alternative...
  50. Abstract, ICPE, 2021 The International Centre of Insect Physiology and Ecology(icipe) has generated new evidence of the immense threat posed by a highly destructive invasive plant, known scientifically asParthenium hysterophorus,towards probable escalation of malaria incidents in East Africa. In...
  51. 2007-01-01 Following several decades of popularity after the Second World War, the use of synthetic herbicides is now experiencing a backlash within the agriculture industry. The increase in organic farming and concerns about potential negative effects on human health and the environment is creating a...
  52. Luna IM, Fernández-Quintanilla C, Dorado J. Is Pasture Cropping a Valid Weed Management Tool. Plants (Basel). 2020 Jan 21;9(2):135. doi: 10.3390/plants9020135. PMID: 31973212; PMCID: PMC7076652. The aim of the present work was to study the feasibility of pasture cropping under the Mediterranean...
  53. 2021-01-01 Satisfying consumer needs through the production of healthy and nutritious agricultural products is a substantial challenge facing modern agriculture. However, agricultural production should be carried out with care for plant health, biological safety of products, and environmental safety while...
  54. WIKTROP is a geographical extension of WIKWIO portal to tropical and mediterranean areas around the world. It aims to strengthen science and technology orientation to achieving food security by enhancing agricultural productivity in the tropical and mediterranean areas.