There are approximately 350,000 known plant species, but less than 1% (about 3,000 species) have economic value and only around 300 species are used for human food and feed. A weed can be defined as a plant that grows where it is not wanted. Weeds negatively impact crops through competition for resources and by harboring pests and diseases. Common agricultural weeds include annual grasses like goosegrass and foxtail, perennial grasses like quackgrass, and broadleaf weeds like chickweed, thistle, and purslane. Weeds cause major crop yield losses each year through competition.

3.  About 350000 species of plants are known to man .Of
these less than 1% or about 3000 have economic
value and only about 300 species are currently used
for food and feed.
 Some plants are termed “weeds” but apparently not
under all circumstances.
 For instance Burmuda grass ( Cynodon dactylon) is a
valueable grass in pastures,but a very troublesome
weed in crop foields.

4.  One 250 years old definition of a weed reads
“a weed is a plant growing where it is not
desired”
 A more relevant definition is “ Weeds are plants
growing in places where, and at times when,
man wants either some other plants to grow or
no plants to grow atall”

5.  weeds are defined as those alien plant species
which are listed
 as “noxious”
 Weed, plant growing where human beings do
not want it to grow

6.  Noxious weed” means an alien plant or parts of an
alien plant that have been designated by
 rule as being noxious or has been declared a noxious
weed by a local advisory board, and
 meets one or more of the following criteria:
 · Aggressively invades or is detrimental to economic
crops or native plant communities;
 · Is poisonous to livestock;
 · Is a carrier of detrimental insects, diseases, or
parasites;
 · The direct or indirect effect of the presence of this
plant is detrimental to the
 environmentally sound management of natural or
agricultural ecosystems

7.  Competition for mineral nutrients.
 Competition for sunlight.
 Competition for water.
 Competition for space
 Parasitism.
 Increase incidence of pests and diseases.
 Reduction of crop quality
 Interferences with cultivation and harvest operations.
 Clogging of irrigation and drainage canals.

8. Crop Loss in
yield
Wheat 2-30%
Maize 20-40%
Rice 20-83%
Sugarcane 10-35%
Oilseeds 10-50%
Vegetables 40-80%

9.  There are many ways on which weeds can be classified into
groups for convenience of planning,interpreting and
recording control measures against them. Some important
classification of weeds used by weed researchers in world for
different purposes are as follows:
 Classification according to anatomy of weeds: Depending
upon their cycle, weeds can be classified as
 Annual
 Biennials
 Perennials

10.  Annual weeds: Annual weeds more commonly
complete their life cycle in one season. An
annual weeds can be either
 Summer annuals
 Kharif annuals e.g. foxtail
 Winter annual e.g. lambs quarter

11.  Biennial weeds complete their life cycle in two
years in the firs year they remain vegetative,
and in the second year they produce flowers
and set seeds.
 E.g. Daucus, Carota, Nulicaulis, etc.

12. Perennial weeds grow for three or more
years.
 E.g. Shallow rooted perennials – Bermuda
grass, Quack grass
 Deep rooted perennials :Johnson grass

13.  a. Monocots
 b. Dicots

14.  Depending upon the development of bark
tissues on their stems and branches, weed can
be classified as :
 a. Woody e.g Lantana
 b. Semi-woody and
 c. Herbaceous species

15.  It is classified into three classes:
 Season bound,
 b. Crop bound,
 c Crop associated

16. Depending upon their occurrences there can be nine important groups
of weeds.
 Crop-land weeds.
 Falloland weeds.
 Grassland or pasture weeds.
 Non-cropland weeds
 Aquatic weeds
 Forest and woodland woods
 Lawn and garden weeds.
 Weeds of plantations.
 Orchard and vineyard weeds

17. Many of weeds in India originated in some
other part of the world.
For e.g. Convolvulus sp –Eurasia, cyperus –
Euphorbia,-Europe, Lantana –Africa

18.  Of the several variable of soil, soil pH is
implicated most frequently with the distribution
of weed species. Weeds, such as red sorrel,
corn sporry and bracken tend to comminute
with weed flora on saline and alkali soils.

19.  Temperature, rainfall, air quality, humidity and
solar energy have pronounced effect on the
distribution of weeds. One could classify weeds
as
 hillside weeds,
 weeds of plains,
 temperate weeds,
 tropical weeds,etc.

20.  Facultative weeds are those weeds that grow
primarily in wild communities but often escape
to cultivated fields. E.g. Opuntia Spp. Obligate
weeds on the contrary, occur only in cultivated
or otherwise disturbed land.
 For e.g.: Field bind weed.

21.  Noxious weeds is a plant arbitrarily defined as
being especially undesirable troublesome and
difficult to control for e.g. Chicory, thistle,
bermuda grass (hariyali

22.  Annual grasses
 Perennial grasses
 Broadleaf weeds
 Miscellaneous

23.  Goosegrass
 Eleusine Indica
 Rabgrasses
 Digitaria spp.
 annual bluegrass
 Poa annua
 yellow foxtail
 Setaria lutescens (glauca)

24.  It is a warm season annual member of the Grass
family (Poaceae) that reproduces by seeds, usually
emerging a few weeks after crabgrass. Goosegrass
is a coarse, bunch-type grass that forms a basal
rosette of prostrate to occasionally upright flattened
stems up to 2 feet long. The stems do not root at
nodes. The root system is fibrous, and the lower
portions of stems near the base are silver or white.
The leaves of goosegrass are dark green, hairy near
the base, and smooth and keeled below. They grow
up to 12 inches long and 1/3 inch wide and are
either flat or folded. Goosegrass flowers are 2 to 10
flattened, finger-like spikes that each resemble a
zipper

26.  It is a warm season annual member of the Grass family that
reproduces by seeds. Seeds germinate at temperatures
between 68 and 95 °F. Yellow foxtail forms a coarse, upright or
prostrate, bunch-type grass. It usually branches at the base
and may root at lower nodes. Growing up to 4 feet tall, yellow
foxtail emerges from a shallow, fibrous root system and
normally has flattened stems that are reddish near the base.
Leaves of yellow foxtail are flat, smooth, and with margins that
are somewhat rough.

28.  Quackgrass
 Agropyon repens
 creeping bentgrass
 Agrosis palustris
 tall fescue
 Festuca undinacea
 Nimblewill
 Muhlenbergia shreberi

29.  common yarrow Achillea millefolium
 wild garlic Allium vineale
 shepherd's purse
 Capsella bursa-pastoris
 mouse-ear chickweed Cerastium vulgatum
 Thistles Cirsium spp.
 prostrate spurge Euphornia supina
 ground ivy Gleochoma hederacea
 Henbit Lamium amplexicaule
 roundleaf mallow Malva neglecta
 black medic Medicago lupulina

30.  yellow woodsorrel Oxalis strictabroadleaf
plantainPlantago major
 buckhorn plantain Plantago lanceolata
 prostrate knotweed Polygonum aviculare
 common purslane Portulacea oleracea
 red sorrel Rumex acetosella
 curled dock Rumex spp.
 common chickweed Stellaria media
 Dandelion Taraxacum Officinale
 white clover Trifolium repens
 Violets Viola spp

31.  Also known as milfoil, thousandleaf, or
woundwort, it is a perennial member of the
Aster family (Compositae) that reproduces
by seeds or short underground rootstocks.
Upright common yarrow stems emerge
from taproots to form a dense mat under
close mowing. The stems are usually not
branched; are smooth to densely covered
with long, soft or woolly grayish-green hairs
and are 4 to 24 inches tall. The tops of the
stems may branch. The alternate, finely
pinnately dissected and fern-like leaves are
soft and covered with hair. The basal
leaves longer than those growing on stem;
stem leaves are 3 to 8 inches long. The
flowers develop in falt-topped clusters at
the top of branches. There are white or
pink ray flowers and yellow disk flowers.
Flowering occurs in June to October.
Common yarrow often occurs in poor,
gravely, droughty, and infertile soils and
does not compete well with turf on rich
soils. It is wear and drought tolerant

32.  It is a cool season perennial member of the
 Lily family (Liliaceae) that reproduces by seeds, aerial bulblets, and underground
bulblets. Most reproduction in northern states is asexual. Beginning growth early in
the spring, wild garlic develops from a bulb into an upright, grass-like plant with an
onion or garlic odor. Stems can grow to more than 3 feet. The leaves of wild garlic
are 2-ranked, slender, hollow, nearly round; and attached halfway down on waxy
stem. The inflorescence is an umbel, 1 to 2 inch diameter. The flowers are small,
greenish-white, and found on stems above the aerial bulblets.
 Flowering occurs during May and June.
 Wild garlic is commonly found in
 poorly-drained, fine-textured,
 fertile soils and thin turf areas

33.  It is a annual or winter annual
member of the Mustard family
(Cruciferae) that reproduces by
seeds. Shepherd's purse emerges
from a thin, branched taproot to
form a rosette of leaves and thin,
erect, usually branched stems to
24 inches tall. The stems are
usually covered with grayish hairs.
Forming a rosette, the basal leaves
are simple, 2 to 5 inches long, and
variably lobed, serrated, or divided.
Leaves on the stems are alternate,
1 to 4 inches long, and are usually
toothed or lobed. The base on
these leaves are ear-like and clasp
or rap around the stem.

34.  It is a perennial member of the
Pink family (Caryophyllaceae) that
reproduces by seeds and
occasionally by creeping stems that
may root where they touch the soil.
Mouse-ear chickweed have
shallow, fibrous roots. The mat-
forming plants grow up to 20
inches tall and have weak, hairy,
spreading stems. Mouse-ear
chickweed leaves are opposite,
dark green, very hairy, and less
than 1 inch long and up to 1/2 inch
wide. They are without petioles and
oval to elliptically shaped. The
small, white flowers have five white
petals that are notched at the tips.
Hairy, leafy sepals are borne
beneath the flowers which occur
April through July.

35.  They are members of the Aster family (Asteraceae). Bull thistle is a biennial that
reproduces by seed, and Canada thistle is a perennial that reproduces by seed and
rhizomes. Bull thistle forms large, coarse plants with spiny leaves, large taproots,
and stems that are heavy and branched at top and hairy when mature. Canada
thistle also forms large, coarse plants with spiny leaves. The large, rhizomatous
underground system form stems that are grooved and branched at top, hairy in
youth, smooth when mature. Bull thistle leaves are deeply-lobed, spiny above and
below, and pubescent beneath. The leaf base joins stem resulting in winged
appearance

36.  It is a warm season member of the
Spurge family (Euphorbiaceae) that
reproduces by seeds. Germination
occurs when soil temperatures
warm to 60 to 65 oF and can
continue as soil temperatures
climb to more than 90 oF. Prostrate
spurge develops a central taproot
from which prostrate stems that
form a flat, extensively branched
mat up to 2 feet in diameter. The
stems exude milky sap when
broken. Leaves of prostrate spurge
are opposite, small, oval, and up to
3/5 inch long. They are sometimes
purple-spotted and/or hairy. The
petioles are short. Prostrate spurge
flowers are very small and
inconspicuous

37.  Also known as creeping Charlie, it is a perennial member of the Mint family
(Lamiaceae) that reproduces by seeds and root pieces. It may form patches
in turf as it creeps on square stems that can grow up to 2 1/2 feet long,
sometimes rooting at the nodes. Occasionally the stems grow in an
ascending fashion. Leaves of ground ivy are opposite, round to kidney
shaped, and 1/2 to 1 1/2 inches in diameter.

38.  It is also known as common mallow, cheeses, dwarf mallow, running mallow, malice,
round dock, and button weed. It is an annual or biennial member of the Mallow
family (Malvaceae) that reproduces by seed. Emerging from a short, straight taproot,
roundleaved mallow develops stems up to 12 inches long. The hairy stems are
horizontal or upright and may be branching at base. The stems do not root as they
touch the ground. The simple, alternate leaves of roundleaved mallow are round to
heart-shaped usually with 5 to 9 shallow lobes or rounded teeth. They are up to 2
1/2 inch across and hairy on both surfaces. The petioles are also hairy and up to 4
inches long.

39.  It is an annual, biennial or perennial member of the Legume family (Fabaceae) that
reproduces by seeds. Black medic is shallow rooted with multi-branched slender,
prostrate, slightly hairy stems spreading 12 to 24 inches. The alternately arranged,
dark green leaves are compound with three, oval leaflets. The center leaflet is
stalked and the side leaflets occur close to the stem. Leaves are sparsely hairy and
the leaflets 1/5 to 3/5 inch long. The 1/8 to 1/6 inch long bright yellow flowers are
clustered on short stems that emerge from the leaf axils. Each cluster is
approximately 1/2 inch long, round, and comprised of up to 50 individual flowers.
Flowering occurs April to October

40.  It is also known as knotgrass. It is a warm season member of the Polygonaceae
(Buckwheat Family) that reproduces by seeds. During early spring, knotweed
resembles a grass with long, dark green leaves when germinating. Later, it forms a
flat mat up to 2 feet in diameter. It has slender, wiry stems; and emerges from a
taproot. There are papery sheaths at each node that give stems a knotted or swollen
appearance. The leaves are alternate, small, narrowly oval, dull bluish-green, and up
to 1 1/4 inches long and 1/3 inch wide. Its flowers are small, borne in clusters in
leaf axils. The buds are purplish opening to white to yellow flowers during June
through October

41.  It is also known as wild portulaca. It is a warm season annual member of the
Purslane family (Portulacaceae) that reproduces by seeds or rooting stem pieces.
Common purslane emerges from a heavy taproot, to develop succulent, smooth,
fleshy stems that are usually purple-red and may root at lower nodes. these many
branched stems reach up to 24 inches long and grow in a prostrate fashion to form
mats. Common purslane leaves are alternate to sub opposite, oval shaped with the
widest point beyond the leaf's middle. Growing up to 1 1/4 inch long, the thick,
fleshy leaves are often clustered near the ends of branches. They are smooth and
without leaf stalks. The yellow flowers of common purslane are borne individually in
the leaf axils or clustered at end of branches. There are five petals. The fruit is a
globular capsule. Flowering occurs in July through September.

42.  It is a perennial member of the Buckwheat family (Polygonaceae) that reproduces by
seeds and occasionally root pieces. Curled dock develops a dense rosette of 6 to 12
inch-long leaves that emerge from a large, fleshy, somewhat branched yellow-orange
taproot on a short crown. At flowering, the inflorescence develops at the top of a
stem that can reach 4 1/2 feet tall. The dark green leaves are simple with a heart-
shaped base. The leaf edges are wavy or curly. Leaves on the stem are alternate and
have short petioles.

43.  It is a cool season perennial of the Aster family (Asteraceae) that reproduces by
seeds and root pieces. Dandelions emerge above a long, sturdy taproot to form
basal rosettes of narrow, deeply lobed leaves. These leaves are 2 to 10 inches long
and up to 2 1/2 inches wide. They have jagged lobes that point back towards stem.
Dandelion inflorescences are yellow, up to 2 inches in diameter, and appear to be
solitary. They are borne on hollow stems that can grow up to 20 inches long, and
held above the foliage. The inflorescences ripen to become round "puffballs" of wind-
dispersed seeds. Flowering period is from early spring to late fall. Dandelions occur
in most lawns throughout the growing season, especially thin turf areas

44.  Weed Description: A perennial trailing or climbing weed with white
morningglory-like flowers that may reach 3 1/3 feet in length. Field
bindweed is primarily a weed of nurseries, agronomic crops, and
fencerows that can be found throughout the United States Weed
Description: A perennial trailing or climbing weed with white
morningglory-like flowers that may reach 3 1/3 feet in length. Field
bindweed is primarily a weed of nurseries, agronomic crops, and
fencerows that can be found throughout the United States

45.  yellow nutsedge Cyperus esculentus

46.  Also known as yellow nutgrass.
It is a perennial member of the
Cyperaceae (Sedge Family) that
reproduces by seeds and tubers
(nutlets) that form at ends of
rhizomes. Individual yellow
nutsedge plants have upright,
grass-like leaves that emerge
from a fibrous root system and
scaly rhizomes. These leaves
emerge from the plant's base,
are 3-ranked, grass-like, and
light yellow-green. They are 1/8
to 1/2 inch wide, up to 3 feet
long, and have parallel veins
with a prominent midvein

47. S.no Botanical name Local names
1. Cyperus rotundus Nut grass, purple nutsedge
2. Cyondon dactylon Bermuda grass, couch grass,star
grass
3. Echinochloa crusgalli Barnyard grass
4. Echinochloa colonum Awnless barnyard grass
5. Eleusine indica Crowfoot grass, goosegrass, wild
finger millett,
6. Sorghum halepense Aleppograss, jhonson grass
7. Imperata cylindrica Sword grass, cogon grass.
8. Eichhornia crassipes Wateryhyacinth

48. S.no Botanical name Local names
10. Chenopodium album Fathen, goose foot, lambsquarter
11. Digitaria sanguinalis Hairy or large crab grass.
12. Convolvulus arvensis Bind weed, field bind weed
13. Avena fatua Wild oats
14. Amaranthus hybridus Pigweed, smooth amaranthus
15. Amaranthus spinosus Prickly amaranth, spiny pigweed
16. Cyperus esculentus Nuttgrass, water grass, yellow
nutsedge.
17. Paspalum conjugatum Sour grass, sour paspalum
18 Rottboellia exaltata Guinea foelgrass, itch grass, Raoul

49. # Weed species English name Average number of
seeds per plant
1. Amaranthus hybridus Pigweed, smooth
amaranthus
196000
2. Chenopodium album Fathen, goose foot, 72000
lambsquarter
3. Cascuta species Ddder 16000
4. Eleusine indica Crowfoot grass,
goosegrass, wild
finger millett,
41200
5. Portulaca oleracea Pigweed purslane 193000

50. Name of
weed
English name Viability of
some weed
seeds in years
Stellaria
media
Common chick
weed
30
Capsella
bursa
pastoris
Shepherds purse 35
Chenopodium
album
Rough pigweed 40
Rumex
crispus
Curled dock 80