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    3E Classification and Identification of Weeds

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    Elline Torres Macay
    1. Weeds are classified based on their taxonomy, morphology, habitat, origin, life cycle, nature of stem, effect of soil pH, and special characteristics. 2. Major categories include grasses, sedges, broadleaved weeds, terrestrial and aquatic weeds, introduced and indigenous weeds, annuals, biennials, and perennials. 3. Further distinctions are made between woody, semi-woody, and herbaceous weeds based on stem texture, and acidophilic, basophilic, and neutrophilic weeds based on soil pH tolerance.

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    3E Classification and Identification of Weeds

    Uploaded by

    Elline Torres Macay
    12 views33 pages
    1. Weeds are classified based on their taxonomy, morphology, habitat, origin, life cycle, nature of stem, effect of soil pH, and special characteristics. 2. Major categories include grasses, sedges, broadleaved weeds, terrestrial and aquatic weeds, introduced and indigenous weeds, annuals, biennials, and perennials. 3. Further distinctions are made between woody, semi-woody, and herbaceous weeds based on stem texture, and acidophilic, basophilic, and neutrophilic weeds based on soil pH tolerance.

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    Module for Crop Protection

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    1. Weeds are classified based on their taxonomy, morphology, habitat, origin, life cycle, nature of stem, effect of soil pH, and special characteristics. 2. Major categories include grasses, sedges, broadleaved weeds, terrestrial and aquatic weeds, introduced and indigenous weeds, annuals, biennials, and perennials. 3. Further distinctions are made between woody, semi-woody, and herbaceous weeds based on stem texture, and acidophilic, basophilic, and neutrophilic weeds based on soil pH tolerance.

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    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
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    12 views33 pages

    3E Classification and Identification of Weeds

    Uploaded by

    Elline Torres Macay
    1. Weeds are classified based on their taxonomy, morphology, habitat, origin, life cycle, nature of stem, effect of soil pH, and special characteristics. 2. Major categories include grasses, sedges, broadleaved weeds, terrestrial and aquatic weeds, introduced and indigenous weeds, annuals, biennials, and perennials. 3. Further distinctions are made between woody, semi-woody, and herbaceous weeds based on stem texture, and acidophilic, basophilic, and neutrophilic weeds based on soil pH tolerance.

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    of 33

    CLASSIFICATION

    AND IDENTIFICATION
    OF WEEDS
    Why Classify and Identify Weeds?
    ➢ Taxonomically, weeds are plants and they are identified
    scientifically using the binomial system of classification just like
    in other organisms.
    ➢ For example, purple nutsedge (Mutha-Tag. Unod-unod-Vis.) is
    known as Cyperus rotundus L. hence, Cyperus refers to the Genus
    and rotundus Species. Linnaeus is the author of the binomial and
    abbreviated as L. or Linn.
    Based on Morphology/Cotyledon Characters
    Based on morphology, weeds are generally divided into:
    • Grasses: monocots, stem is hollow except at nodes, ligulate,
    alternate or opposite leaves, long, narrow leaves with
    parallel veins. Ex. Digitaria, Cynodon
    • Sedges: monocots, stem is angular and solid, ligules are absent,
    leaves are arranged in whorls around the stem, have
    modifies rhizomes. Ex. Cyperus, Scirpus
    • Broadleaved Weeds: mostly dicots having broad leaves with netted
    venation. Ex. Eclipta alba, Amaranthus spinosus, Portulaca
    oleracea
    • Algae: Chlorella, Spirogyra, Cladophora
    • Ferns: seedless vascular plants that produce spores. Ex. Marsilea
    crenata, Salvinia molesta
    Digitaria Scirpus Mimosa pudica

    Chlorella Marsilea crenata Salvinia molesta


    1. Grasses
    - Belong to Poaceae/Graminae family
    - Annual or perennial
    - Stem known as culm is round and hollow
    - Presence of nodes and internodes
    - Leaves which are narrow with parallel venation arise in
    alternate manner along the stem; leaf sheath is the lower
    portion of the leaf and the upper portion is called the blade
    - Presence of hairy membranous structure, the ligules which is
    found at the junction of the leaf blade and leaf sheath
    - Examples: Rottboellia cochinchinensis (itchgrass)
    Echinocloa glabrescens (barnyard grass)
    Imperata cylindrica (cogon)
    2. Sedges
    - Belong to the Cyperaceae family
    - Annual or perennial
    - Stem is solid and triangular
    - Absence of ligule and nodules
    - Leaf sheaths are forming a tube around the stem
    - Presence of underground bulbs and tubers in perennial sedges
    - Example: Cyperus rotundus (purple nutsedge)
    3. Broadleaf
    - Belong to other plant families
    - Generally are dicots but few species are monocots
    - Fully expanded leaves with netted venation
    - Leaves are arranged in different manners arising either on
    opposite or alternate manner
    - Examples: Ageratum conyzoides (tropic ageratum)
    Monocharia vaginales (gabing uwak)
    Amaranthus spinosus (spiny amaranth)
    Based on Habitat
    Depending upon the place of their occurrence, they are classified into:
    1. Terrestrial Weeds
    Crop Land Weeds - weeds in field, e.g. Echinochloa in rice.
    Non-crop Land Weeds - weeds in waste lands, e.g. Tribulus terrestris,
    Xanthium strumarium.
    Grassland Weeds - e.g. Vernonia cinerea and Rumex spp.
    Weeds of Lawns & Public Parks - e.g. Lippia nodiflora and Eleusine
    indica.
    Orchard or Garden Weeds - e.g. Euphorbia geniculata, Imperata
    cylindrica, Acalipha indica.
    Weeds of Plantation Crops - e.g. Euphatorium spp., Mikania micrantha
    Roadside Weeds - e.g. Euphorbia, Lantana camara, Hyptis suaveolens
    and Prosopis juliflora
    Echinochloa Tribulus terrestris Eleusine indica

    Imperata cylindrica Mikania micrantha Hyptis suaveolens


    2. Aquatic Weeds
    Submersed Weeds - e.g. Utricularia stellaris, Ceratophyllum
    demersum, Hydrilla verticillata and
    Vallisneria spiralis
    Emersed Weeds - e.g. Nelumbium speciosum, Jussieua repens
    Marginal Weeds - e.g. Typha, Polygonum, Alternanthera, Ipomoea
    Floating Weeds - e.g. Pistia stratiotes, Salvinia molesta
    Hydrilla verticillata Nelumbium speciosum

    Typha latifolia Pistia stratiotes


    Based on Origin
    • Indigenous Weeds (Apophytes)
    - All the native weeds of the country are coming under this group
    and most of the weeds are indigenous.
    - Ex. Acalypha indica, Abutilon indicum, Sorghum halepense,
    Cyanodon dactylon and Echinochloa colona
    • Introduced or Exotic weeds or Alien
    - These are the weeds introduced from other countries. These
    weeds are normally troublesome and control becomes difficult.
    - Ex. Parthenium hysterophorus, Acanthospermum hispidum,
    Eichhornia crassipes, Argemone mexicana, Lantana camara
    and Croton bonplandianus
    • Antrophytes - When man aids in its introduction
    Parthenium hysterophorus Lantana camara
    from USA from Sri Lanka by birds

    Orobanche sp. Eichhornia crassipes


    from Europe from South America
    Based on Association

    1. Season Bound Weeds


    - They are seen in that
    particular season
    irrespective of crop.
    - These are either summer
    perennial annuals (Sorghum
    halepense) or winter
    perennial annuals (Cirsium
    arvense). Phalaris minor and
    Avena fatua are winter
    season annuals.
    2. Crop Bound Weeds

    Parasitic Weeds - weeds which are usually dependent on the host


    crop partially or fully for their nourishment
    Root Parasites - those parasites which attack roots
    a. Complete Root Parasite, e.g. Orobanche (broom rape) in tobacco
    b. Partial Root Parasite, e.g. Striga sp. (witch weed) in millets

    Stem Parasites - those which attack shoot of other plants


    a. Complete Stem Parasite, e.g. Cuscuta (dodder) in lucern
    b. Partial Stem Parasite, e.g. Loranthus in fruit crops
    Orobanche sp. (broom rape) Cuscuta (dodder)
    3. Crop Associated Weeds
    - Such weeds grow along with
    the crop due to their
    requirement of microclimate
    and habitat and survive along
    the crop in the form of
    mimicry.
    - Ex. Amaranthus viridis and
    Echinochloa crusgalli are
    associated with rice
    Based on Life Cycle/Ontogeny

    1. Annuals - are further classified into:


    a. Kharif Season Annuals,
    e.g. Setaria glauca Setaria glauca
    b. Rabi Season Annuals,
    e.g. Chenopodium album, Avena
    fatua, Phalaris minor
    c. Summer Season Annuals, Chenopodium album
    e.g. Argemone mexicana
    d. Multi Season Annuals,
    e.g. Echinochloa colona, Eclipta alba
    Eclipta alba
    2. Biennials

    Cirsium vulgare

    Wild Daucus carota


    3. Perennials

    a. Simple Perennial: b. Bulbous Perennial: c. Creeping


    Ipomoea carnea Wild onion (Allium Perennial: Sorghum
    vineale) halepense
    Based on Nature of Stem/Body Texture

    Depending upon development of


    bark tissue on their stems and
    branches, weeds are classified
    into:
    1. Woody Weeds (Brush Prosopis juliflora
    Weeds):
    e.g. Lantana camara, Prosopis
    juliflora (mesquite),
    Zizyphus rotundifolia
    weeds (wild plum) Zizyphus rotundifolia
    2. Semi-Woody Weeds:
    Croton sparsiflorus

    3. Herbaceous Weeds:
    Weeds with green,
    succulent stems are of
    most common occurrence
    around us.
    Ex. Amaranthus viridis Croton Chenopodium
    and Chenopodium sparsiflorus album
    album
    Based on Soil pH

    1. Acidophile Weeds
    - habitat acid soils,
    e.g. Rumex acetosella,
    Pteridium spp.

    Rumex acetosella Pteridium sp.


    2. Basophile Weeds
    - dominate in saline and
    alkaline soil
    e.g. Salsola spp. dominate
    saline soils whereas
    Cressa erecta and
    Sporobolus diander
    dominant in alkaline
    soils. Sporobolus
    Salsola sp.
    diander
    3. Neutrophile Weeds
    - weeds thriving in neutral soils
    e.g. Acalypha indica
    Based on Special Classification

    1. Poisonous Weeds
    e.g. Datura fastuosa, D.
    stramonium and D. metel
    The berries of Withania somnifera
    are also poisonous.

    2. Parasitic Weeds
    The parasitic weeds are either
    total or partial for their growth.
    e.g. Orabanche, Cuscuta Datura fastuosa
    3. Obligate Weeds - Occur only on cultivated Convolvulus arvensis in
    land or otherwise disturbed land Wheat Field
    and disappears when the land is
    not disturbed for 2-3 years and
    kept as fallow, e.g. Bind weed
    (Convolvulus arvensis)
    4. Noxious Weeds - These weeds are
    arbitrarily defined as being
    Saccharum spontaneum
    undesirable, troublesome & in Vegetable Area
    difficult to control. They have
    immense capacity of reproduction
    & high dispersal capacity, e.g.
    Argemone mexicana, Cyperus
    rotundus, Parthenium, Cynodon
    dactylon, Lantana camara,
    Saccharum spontaneum
    5. Objectionable Weeds - Weeds which
    produce seeds that are difficult
    to separate once mixed with crop
    seeds. The mixture of seeds in
    mustard. e.g. Argemone
    Argemone mexicana
    mexicana

    6. Facultative Weeds or Apophytes -


    Weeds which are wild in the
    community and sometimes
    found in cultivated areas, e.g.
    Parthenium hysterophorus Parthenium hysterophorus
    7. Associated Weeds (Non-Parasitic
    Weeds) - Weeds which are not
    dependent on other crop for its
    development and growth. e.g. Cichorium
    intybus and Avena fatua
    Cichorium intybus

    8. Industrials Weeds - Weeds invading


    areas around buildings, highway,
    railway lines, fence rows, electric and
    telephone pole bases, etc. e.g.
    Parthenium, Alternanthera sessilis
    Alternanthera sessilis

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