After completing 3 Units in this Lesson, you have learned to answer:

1
Module 9 Weeds and Weed Control
Virtual Academy for the Semi Arid Tropics
Lessons
Modules

Lesson 1 Weeds and Weed Competition

• After completing 3 Units in this Lesson, you
  have learned to answer
• Why weed control is important in sorghum crop?
• When is the critical period for weed competition
  in sorghum crop?
• Name few important broadleaf weeds in sorghum
  crop?
• Name few important grass weeds in sorghum crop?
• Name few important sedges that compete with
  sorghum crop?

Course on Sorghum Production Practices
2
Module 9 Weeds and Weed Control
Virtual Academy for the Semi Arid Tropics
Lessons
Modules

Lesson 1 Weeds and Weed Competition

• After completing 3 Units in this Lesson, you
  have learned to answer
• What is Striga?
• How striga affects sorghum crop?
• What cultural methods you practice to control
  Striga?
• What chemical methods help in controlling Striga?
• What good husbandry practices you will adopt to
  control Striga in sorghum crop?

Course on Sorghum Production Practices
3
Module 9 Weeds and Weed Control
Virtual Academy for the Semi Arid Tropics
Modules

The 3 Units in this Lesson are Unit 1
Weed Competition in Sorghum Unit 2 Weeds in
sorghum Unit 3 Striga
Click Unit to select the Unit
Course on Sorghum Production Practices
4
Units
Lesson 1 Weeds and Weed Competition
Unit 1 Weed Competition
Sorghum being mainly grown during rainy season
encounters several weeds which grow luxuriantly
and dominate during this season as compared to
rabi/summer season.
Weeds in young sorghum crop
5
Units
Lesson 1 Weeds and Weed Competition
Unit 1 Weed Competition
Weeds in sorghum crop compete with the crop for
nutrients, water, and light as with other
crops. Weeds are more competitive when moisture
is limiting and especially under drought
situation. When young, grain sorghum does not
compete well with weeds.
Weeds in young sorghum crop
6
Units
Lesson 1 Weeds and Weed Competition
Unit 1 Weed Competition
Unless good weed control is achieved, substantial
yield losses will occur. Yield loss of more than
70 due to weeds compared to weed free crop was
reported from weed control experiments.
Weeds free young sorghum crop
7
Units
Lesson 1 Weeds and Weed Competition
Unit 1 Weed Competition
It was found necessary to keep the crop weed free
from 15 to 40 days after sowing. Weed
competition is critical during second to third
fortnight after sowing.
Weeds free young sorghum crop
8
Units
Lesson 1 Weeds and Weed Competition
Unit 1 Weed Competition
Early planting of sorghum avoids competition from
the flush of weeds that comes up with continuous
rains during the early monsoon period.
Early planted sorghum without weeds
9
Units
Lesson 1 Weeds and Weed Competition
Unit 2 Weeds in sorghum
A variety of weeds are associated with sorghum
crop. The type of weeds vary from place to
place depending on soil type, season and
environment where sorghum is grown. These weeds
comprise of diverse plant species of annual
grasses and seasonal broad leaved weeds.
10
Units
Lesson 1 Weeds and Weed Competition
Unit 2 Weeds in sorghum
Weed problems in grain sorghum include perennial
grasses such as Johnson grass and Bermuda grass,
annual grasses such as Crabgrass and Goose grass,
and many broadleaf weeds. The list of major
weeds that grow in ground crop are shown with
their images in the following screens
11
Units
Lesson 1 Weeds and Weed Competition
Unit 2 Weeds in sorghum
Common broad-leaf weeds Botanical name Common
Name Abutilon indicum Indian
mallow Alysicarpus sp. One-leaf
clover Argemone mexicana Mexican
poppy Celosia argentina White cock's comb
Click on the underlined word to see the weed
image
12
Units
Lesson 1 Weeds and Weed Competition
Unit 2 Weeds in sorghum
Common broad-leaf weeds Botanical name Common
Name Borreria articularis Button
plant Gynondropsis (Cleome) spp. Wild spider
flower Digera arvensis Kundra Corchorus
olitorius Jew's mallow Click on the underlined
word to see the weed image
13
Units
Lesson 1 Weeds and Weed Competition
Unit 2 Weeds in sorghum
Common broad-leaf weeds Botanical name Common
Name Portulaca spp. Common purslane Vernonia
cinerea Little iron weed Leucas aspera
Dronapushpi Xanthium strumarium Cocklebur
Click on the underlined word to see the weed
image
14
Units
Lesson 1 Weeds and Weed Competition
Unit 2 Weeds in sorghum
Common broad-leaf weeds Botanical name Common
Name Anagallis arvensis Scarlet
Pimpernel Bidense pilosa Spanish needle
Eclipta spp. False daisy Ipomea
spp Morning glory Click on the underlined
word to see the weed image
15
Units
Lesson 1 Weeds and Weed Competition
Unit 2 Weeds in sorghum
Common broad-leaf weeds Botanical name Common
Name Tridax procumbence Tridax daisy, wild
daisy Euphorbia spp. Spurge Amaranthus
spp. Pigweed Mollugo verticillata Carpet-wee
d Click on the underlined word to see the weed
image
16
Units
Lesson 1 Weeds and Weed Competition
Unit 2 Weeds in sorghum
Common grass (monocots) weeds Botanical
name Common Name Chloris spp. Finger grass
Digetaria sanguinalis Crabgrass Dactylocte
nium aegyptium Crowfootgrass Echinocloa
spp. Barnyard grass Click on the underlined
word to see the weed image
17
Units
Lesson 1 Weeds and Weed Competition
Unit 2 Weeds in sorghum
Common grass (monocots) weeds Botanical
name Common Name Commelina spp. Benghal
dayflower Paspalum distichum Water
couch Eleusine indica Goose grass Eragrostis
spp. Love grass Setaria spp. Foxtail Cynodo
n dactylon Bermuda grass Click on the
underlined word to see the weed image
18
Units
Lesson 1 Weeds and Weed Competition
Unit 2 Weeds in sorghum
Common sedges Botanical name Common
Name Cyperus rotundus Purple nut
sedge Cyperus esculentus Yellow nut
sedge Cyperus defformis Nut sedge Cyperus
compressus Nut sedge Click on the underlined
word to see the weed image
19
Units
Lesson 1 Weeds and Weed Competition
Unit 3 Striga
Striga is a very important weed in sorghum
cultivation. Unlike other weeds, which compete
for water and nutrients Striga, as a root
parasite, literally sucks the life out of sorghum
plants. In doing so, growth is stunted and yields
are greatly reduced.
Sorghum affected by Striga
20
Units
Lesson 1 Weeds and Weed Competition
Unit 3 Striga
Striga has been given the common name of
"witchweed" because of attaching to the roots and
robbing the host of water and nutrients.
Striga infested sorghum field
21
Units
Lesson 1 Weeds and Weed Competition
Unit 3 Striga
There are different species of Striga. The
Striga found in India is most often has white
flowers. But, Striga plants with yellow, pink or
purple flowers are also common.
White flowered Striga
22
Units
Lesson 1 Weeds and Weed Competition
Unit 3 Striga
Pink flowered Striga
Mauve flowered Striga
Red flowered Striga
23
Units
Lesson 1 Weeds and Weed Competition
Unit 3 Striga
Depending upon the extent of infestation, 30-60
of reduction in grain yield can occur. Striga
infestation is most severe in low moisture and
low fertility soils. Thousands of very small
seeds are produced by a single plant of Striga.
These seeds can remain dormant but viable for
many years.
Small Striga seeds compared to sorghum and maize
24
Units
Lesson 1 Weeds and Weed Competition
Unit 3 Striga
Striga plants emerge from the soil adjacent to
sorghum plants and produce many upright green
stems with pink to white flowers.
25
Units
Lesson 1 Weeds and Weed Competition
Unit 3 Striga
Flowering can begin within 2 weeks and seeds
begin to mature 2-4 weeks later. The seed
capsules may contain 400-500 seeds and a single
plant may produce 20,000 seeds. Mature seeds
are dispersed by wind, rainwater, cultivation,
soil on tools, or even grazing and manure
fertilization.
26
Units
Lesson 1 Weeds and Weed Competition
Unit 3 Striga
Striga Life-Cycle
27
Units
Lesson 1 Weeds and Weed Competition
Unit 3 Striga
Control measures Physical control Hand pulling
at too early stage may break the shoot and reduce
the rapid growth. Sparse infestation should be
hand pulled shortly before flowering to prevent
build up of seed. Such hand pulling should
continue through to harvest and beyond so long as
flowering is occurring.
28
Units
Lesson 1 Weeds and Weed Competition
Unit 3 Striga
Control measures Cultural control It has been
noted that sorghum plant shading can restrict
Striga growth when generous soil fertilizer is
applied. In areas of high rainfall, factors
such as high plant populations, recommended
fertility levels, and good weed control encourage
lush crop growth and shading in spite of Striga
parasitism. This is not feasible in moisture
stressed rainfed areas.
29
Units
Lesson 1 Weeds and Weed Competition
Unit 3 Striga
Control measures Cultural control Crop rotation
should be practiced with trap crops which
stimulate Striga seeds to germinate without
themselves being parasitized. Crops claimed to
be effective include cotton, sunflower,
groundnut, castor, dolichos bean, and linseed.
Unfortunately once a severe infestation has
developed, it may take many years to reduce
Striga population in the field to non-damaging
level.
30
Units
Lesson 1 Weeds and Weed Competition
Unit 3 Striga
Control measures Cultural control Growing of
available resistant varieties help to reduce
Striga build up in the field as Striga resistance
is mainly associated with low yield and poor
grain quality of the resistant variety.
SAR 34 a Striga resistant variety
31
Units
Lesson 1 Weeds and Weed Competition
Unit 3 Striga
Control measures Chemical control As Striga is
a broadleaf plant, pre-plant herbicides such as
Atrazine, Goal, and Flex show some effect though
not efficient enough to be justified.
Post-emergence use of 2,4-D is effective when
sprayed on the Striga leaves. Though low in
cost, sorghum is vulnerable to stalk twisting and
lodging if 2,4-D is sprayed into the leaf whorl.
Spraying should only be done trained labor and
cautioned to the hazards.
32
Units
Lesson 1 Weeds and Weed Competition
Unit 3 Striga
Control measures In summary, control of Striga
infestation is difficult and requires an
integrated approach. Non-host crops must be
rotated (for two years in heavily infested
fields) with resistant sorghum varieties.
33
Units
Lesson 1 Weeds and Weed Competition
Unit 3 Striga

• Control measures
• Following good practices will help reducing
  striga effect in sorghum crop
• plant populations and fertility adjusted for
  soil moisture availability to maximize
  shading,
• weeding and Striga control through hand
  pulling and perhaps limited 2,4-D spraying,
  and finally
• care not to spread seeds of Striga though
  fodder, manure or contaminated soil on
  tillage tools.

34
Module 9 Weeds and Weed Control
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Lessons
Modules

Abutilon indicum Indian mallow
Course on Sorghum Production Practices
35
Module 9 Weeds and Weed Control
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Alysicarpus sp. One-leaf clover
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Module 9 Weeds and Weed Control
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Argemone mexicana Mexican poppy
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Module 9 Weeds and Weed Control
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Celosia argentina White cock's comb
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Module 9 Weeds and Weed Control
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Borreria articularis Button plant
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Module 9 Weeds and Weed Control
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Cleome sp. Wild spider flower
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40
Module 9 Weeds and Weed Control
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Digera arvensis Kundra
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41
Module 9 Weeds and Weed Control
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Corchorus olitorius Jew's mallow
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42
Module 9 Weeds and Weed Control
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Euphorbia hirta Spurge
Euphorbia purviflora
Course on Sorghum Production Practices
43
Module 9 Weeds and Weed Control
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Portulaca pilosa
Portulaca oleracea Common purslane
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Module 9 Weeds and Weed Control
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Vernonia cinerea Little iron weed
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Module 9 Weeds and Weed Control
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Leucas aspera Dronapushpi
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Module 9 Weeds and Weed Control
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Xanthium strumarium Cocklebur
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Module 9 Weeds and Weed Control
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Amaranthus spp. Pigweed
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Module 9 Weeds and Weed Control
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Anagallis arvensis Scarlet Pimpernel
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49
Module 9 Weeds and Weed Control
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Bidense pilosa Spanish needle
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Module 9 Weeds and Weed Control
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Mollugo verticillata Carpet-weed
Course on Sorghum Production Practices
51
Module 9 Weeds and Weed Control
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Commelina spp. Benghal dayflower
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Module 9 Weeds and Weed Control
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Eclipta alba
Eclipta prostrata
False daisy
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53
Module 9 Weeds and Weed Control
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Ipomea spp. Morning glory
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54
Module 9 Weeds and Weed Control
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Tridax procumbence Tridax daisy, wild daisy
Course on Sorghum Production Practices
55
Module 9 Weeds and Weed Control
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Chloris gayana Feather Finger grass
Chloris barbata Swollen Finger grass
Course on Sorghum Production Practices
56
Module 9 Weeds and Weed Control
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Digitaria sanguinalis Crabgrass
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57
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Dactyloctenium aegyptium Crowfootgrass
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58
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Echinocloa spp. Barnyard grass
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59
Module 9 Weeds and Weed Control
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Paspalum distichum. Water couch
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60
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Eleusine indica Goose grass
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61
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Eragrostis spp. Lovegrass
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Setaria spp. Foxtail
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Cyperus rotundus Purple nut sedge
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Cyperus compressus Nut sedge
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Cyperus defformis Nut sedge
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Cyperus esculantus Yellow nut sedge
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Cynodon dactylon Bermuda grass
Course on Sorghum Production Practices