MODULE 7 PT 1

• Weed management


  Being used (most of the time) in reference to control which suggest "killing" or "eradicating". Basically the same in meaning.
• Weed management


  A part of a more general problem of vegetation management, wherein conditions are created favoring desirable and suppressing undesirable species
• Weed management


  • Identification of weeds and their level of infestation
  • Biology and ecology of the prevalent species
  • Competitive effects and CTL
  • Technically effective, economically, viable and environmentally safe methods of control
• Weed Management Strategies


  • Prevention
  • Eradication
  • Control
• Prevention


  Measures that prevent or arrest the introduction, establishment, and spread of weeds in areas that are not currently infested with these plants species
• Eradication


  Measures wherein weed species are totally killed or eliminated including seeds/vegetative propagules in such a way that it will not reappear in the area unless reintroduced later
• Control


  Measures whereby weed infestations are reduced but not necessarily eliminated
• Means of preventing weed infestations

  • Establishment and compliance with strict quarantine laws
  • Use of clean/certified seeds free of weed seeds
  • Not allowing weeds to reproduce sexually/asexually
  • Burying and burning of residues and uprooted weeds
  • Sanitation of non-crop areas on the farm
  • Keeping levees and irrigation canals free of weeds, screening of irrigation water
  • Cleaning of farm machines/tools
  • Keeping grazing animals out of crop field – manures contain weed seeds
• Eradication


  • Being used in small areas because it is difficult to attain and expensive
  • Used in high value areas like greenhouses, ornamental plant beds and containers and certain high value vegetative crops
  • Difficult to achieve is eradication of propagules in the soil
• Control


  • The aim is to reduce the weed population to a level which is not significantly injurious to crop. Weed control may range from poor to excellent level.
  • The degree of weed control is dependent on: Characteristics of weed involved, Effectiveness of the method/s used, Benefits/costs and resources available
• Physical/Mechanical Weed Control Methods

  • Hand pulling
  • Hoeing
  • Mowing
  • Flooding
  • Mulching
  • Flaming
  • Tillage
• Hand pulling


  • Effective in controlling weed seedlings but not in established perennials
  • Effective between crop plants in rows difficult to reach by hoe or cultivator
  • Labor intensive; free from costly machinery and chemicals
  • Most practical for small farmers with limited resources
• Hoeing


  • Highly effective means of weed control
  • May be effective against perennials if practiced at intervals of 1-2 weeks during the growing season
• Mowing


  • Cutting of weed foliage at a specified height
  • May kill weeds or at least prevent seed production
  • Deplete underground food reserves of perennial weeds
  • Most effective on tall growing plants and annual broadleaf weeds
• Flooding


  • Killing the weeds by depriving them with air (suffocation); unable to carry on photosynthesis
  • Deprive weeds of oxygen – kill existing weeds
  • Suppress germination of weed seeds
  • Controls herbaceous perennial weeds
  • Flooding will not significantly affect viability of dormant annual weed seeds in the soil
  • Generally need 6-10 inches of standing water for 3-8 weeks
• Mulching


  • Inhibit weed growth
  • Prevent photosynthesis
  • Reduce erosion and conserve moisture
  • Prevent soil crusting
  • Improve biological activity in the soil
• Flaming


  • Use in non-crop areas
  • Selective burning – kill only the weeds; usually repeated at intervals of 5-10 days
  • Non-selective burning – use in land clearing or for sanitation in non-cropped situation
  • Direct flame toward the ground – may be aimed between crop rows
  • Heating of cytoplasm causes cell rupture
  • Symptoms of injury and death may take several hours to be noticeable
  • Effective for crops that have the meristem below ground (protected) or are tall with woody stems
• Tillage


  • Weed control
  • Breaking of soil to aid emergence of seedlings
  • To prepare the land for irrigation in furrow areas
  • Create favorable conditions for bacterial activity in soils resulting in rapid decomposition of organic matter
  • Create favorable conditions for weed germination near soil surface which can be controlled by follow up operations
• Primary tillage equipment


  • Moldboard plow
  • Disk plow
  • Chisel plow
  • Philippine Native Plow
• Secondary tillage equipment


  • Power driven tiller
  • Harrow
  • Weeder
  • Cultivator
• Special Tillage Practices


  • Delayed tillage
  • Blind tillage
  • Zero tillage
• Perennial Weeds


  • The operative principle for use of tillage for control is carbohydrate depletion
  • When tillage is done frequently, the management assumption is that reserve will be depleted and plants will die because of exhaustion of root reserves and increased susceptibility to other stresses
  • Unfortunately, root reserves are vast and outlast human patience and time
  • If you till a creeping perennial only once you are just encouraging it!
• Soil Solarization


  • Utilization of the heat of the sun to control weeds
  • Solar energy heats soil to temperatures high enough to kill weed seeds and pathogens
  • Requires extended periods of full sun (4-8 weeks), so most suited to tropics and semi-tropic regions where air temperature naturally exceeds 40oC
  • Greatest effect is in the top 4-6 inches of soil
• Other Physical/Mechanical Methods


  • Heat and steam used for sterilizing soil for greenhouses. Kills weed seeds and plant pathogens
  • Electricity can be used but has not found commercial success
  • Cryogenic weed control
  • Microwave weed control
  • Air Gun