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CROP PROTECTION > LESSON 3,4 AND 5 > Flashcards

LESSON 3,4 AND 5 Flashcards

1
Q

A plant growing where it is not wanted (Oxford Dictionary)
● Any plant or vegetation, excluding fungi, interfering with
objectives or requirements of people (European Weed
Science Society)
● A plant that is especially successful at colonizing and
proliferating in disturbed site.

A

WEED

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2
Q

is the study of weeds and their control.
● It is an offshoot of plant physiology having evolved from the study of
plant growth regulators.
● Its main goal is the formulation of most effective, economical, and
satisfactory methods of controlling weeds.

A

● Weed science

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3
Q

The damage caused by weeds are not visible as those caused by
insects and diseases.
● Seldom results to total crop failure.
● Crops and weeds are always associated together.

A

Why weeds as pest are not recognized early

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4
Q

break up the soil to make nutrients
more readily available

A

Modern hoe

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5
Q

l first coined the term
“weed” in 1931 in the book
“Horse Hoeing Husbandry”
Weeds are the plants which
grow where they are not
wanted

A

Jethro Tull

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6
Q

were largely replaced by monoculture systems
and chemical weed control however, crop rotation has become an integral
part of weed management in organic farming as well as integrated weed
management practices in conventional farming systems.

A

Rotation practices w

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7
Q

different crops in recurrent succession

A

crop rotation

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8
Q
  1. Rotation of competitive crop and non-competitive crops
  2. Use of weeds suppressing crops as cover crops
  3. Under sowing cereals with fodder legumes
  4. Use of catch crop or trap crop
A

Principle of crop rotation

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9
Q

Chemical weed control was first mentioned when describing the effects of mainly—————and their ability to offer some form of
selective weed control.

A

inorganic substances

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10
Q

● Some of the chemicals with herbicidal activity prior to the 1940’s were

A

salt, iron sulfate, sulfuric acid, and copper sulfate.

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11
Q

● Weed science received a major boost as a valid scientific discipline with
the synthesis of

A

2,4-D effective herbicide.

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12
Q

is an example of this technology; it was introduced during the
1970’s and offered excellent weed control at these lower use rates, and
with little harm to the environment as indicated in the ranking of the World
Health Organization

A

Glyphosate

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13
Q

Characteristics of a Weed

A

A unique characteristic of a weed is its excellent adaptation to the
disturbed environment. They are able to occupy the ecological spaces
left open in those environments altered by man for his use.
● They have rapid vegetative growth.
● They reproduce rapidly and mature early.
● Most weeds are very prolific and produce abundant seeds.
● They have the ability to survive and adapt to adverse conditions.
● Propagules possess dormancy or can be induced to become dormant
under unfavourable conditions.
● Adapted to crop competition.

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14
Q

Advantages/Benefits of Weeds

A

Weeds when ploughing under, add nutrients, organic matter.
● Weeds check winds or water erosion by soil binding effect of their roots
(underhand).
● Useful as fodder for castles (Hariyali) & vegetable by human beings
(Ghol, Tandulja)
● Have medicinal value, Leucas aspera is used against snake bite, oil of
satyanashi seed is useful against skin diseases, nuts of lavala are used
in making scents (Incense sticks).
● Weeds can also be valuable indicators of growing conditions in a field, for
example of water levels, compaction and pH.

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15
Q

Disadvantages of Weeds

A

● Reduction in crop yield
● Increase in the cost of cultivation.
● The quality of field produce is reduced.
● Reduction in quality of livestock produce
● Harbour insect-pests & disease pathogens
● Check the flow of water in irrigation channels
● Secretions are harmful
● Harmful to human beings and animals
● Cause quicker wear & tear of farm implements.
● Reduce the value of the lands

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16
Q

weeds that are more or less found in every farm but not
exceptionally injurious and are readily controlled by good farming practices.

A

Common weeds

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17
Q

weeds that are particularly undesirable because of their certain
undesirable characteristics, like the presence of an extensive perennial
underground system which enable to resist the most determined effort to
control.

A

Noxious weeds

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18
Q

Examples of Noxious Weeds

A

Crab grass (Digitaria spp.) Pig weed (Amaranthus spp.)

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19
Q

Examples of Common Weeds

A

Siam weed (Chromolaena odorata)
Milk weed (Euphorbia heterophylla )

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20
Q

Are members of the family Gramineae (Poaceae) which range from
small, twisted, erect, or creeping annuals and perennials.
● Stems are called culms with well -defined nodes and internodes.
● Leaves arise alternately in two rows from the nodes.
● The leaf is composed of two parts, the leaf sheath and leaf blade.

A

Grasses

Echinocloa colonum Cynodon dactylon

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21
Q

Are members of the family Cyperaceae has a narrow-elongated leaf but
differs from grasses by their distinguishing triangular stem.
● The leaves are mostly from the base having modified stem with or
without tubers.

A

Sedges

Cyperus rotundus Fimbristylis miliaceae

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22
Q

Are members of the family Dicotyledonae and Monocotylidonae
characterized by shorter but wider leaves with either parallel or netted
venation like pickerel weed (parallel veins) or three-lobed morning glory
(netted veins).
● All dicotyledon weeds are broad leaved weeds

A

Broadleaves

Digera avensis
Portulaca oleracea
Tridax procumbens

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23
Q

is one that matures in one growing season or within one
year. Example: barnyard grass and goose grass

A

Annual weed -

Barnyard grass (Echinochloa crus-galli) Goose grass (Eleusine indica)

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24
Q

is one that matures in more than one growing season or
year. Example: purple nutsedge and bermuda grass

A

Perennial weed

Purple nutsedge (Cyperus rotundus)
Several purple nutsedge plants linked by a network of
rhizomes.

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25
Q

is one that reproduces by means of seeds or seed propagules (is a plant part
of which is capable of regenerating its own species). Example: barnyard grass

A

Sexual weed

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26
Q

is one that reproduces by means of vegetative propagules. Examples of
vegetative propagules are:

A

Asexual weed -

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27
Q

– is a modified underground stem with buds and scales; Example: cogon grass

A

rhizome –

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28
Q

is a modified aboveground stem that creeps and roots at the side; Example:
Bermuda grass

A
  • stolon
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29
Q

is a short thickened underground stem; Example: purple nutsedge

A
  • tuber
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30
Q

is a baby plant that arises from the mother plant; Example: water lettuce

A
  • off-shoot –
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31
Q

stem stands upright; ex. Itch grass (Rottboellia cochinchinensis)

A

Erect –

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32
Q

– lying along the ground or along a
surface, with the extremity curving upward. ex.
Goosegrass (Eleusine indica)

A

Decumbent

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33
Q

having short stem and short internode;lying
face down on the ground. ex. jungle rice (Echinochloa
colona)

A

Prostate

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34
Q

day flower
(Commelina communis)

A

Ascending

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35
Q

whose stems spread along
the ground and root by means of
adventitious roots. ex. bermuda grass
(Cynodon dactylon)

A

Creeping

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36
Q

stem coils round the support. ex.
three-lobed morning glory (Ipomea triloba)

A

Twining

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37
Q

is one that grows well in lowland or moist soil; Ex. barnyard
grass and water lettuce

A

Wetland weed

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38
Q

s one that grows well in upland or drier soil; Ex. itchgrass
and three-lobed morning glory

A

Dryland weed

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39
Q

is an inflorescence in the main axis with at least primary and
secondary branching; Ex. barnyard grass

A

Panicle

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40
Q

is a compound structure whose members arise and diverge from
the same point, like fingers of the hand; Ex. goosegrass

A

is a compound structure whose members arise and diverge from
the same point, like fingers of the hand; Ex. goosegrass

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41
Q

is more of less a conical inflorescence with flowers arising
laterally from a common axis; Ex. itchgrass

A

Raceme

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42
Q

is an inflorescence in which a number of divergent flowers arise
from the same point. Ex. purple nutsedge

A

Umbel

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43
Q

Weeds are classified:

A

Based on outward appearance or gross morphology
● Based on maturity period or life cycle
● Based on manner of reproduction
● Based on habit of stem growth
● Based on habitat or place for preferred growth
● Based on the inflorescence or floral structure of the plant

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44
Q

In many situations, the first one-third to one-half on the
growth cycle of the crop is sensitive to weed
competition.
* This stage is called the

A

critical period of competition.

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45
Q

for nutrient, moisture, light and space

A

Direct competition

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46
Q

– through exudation and/or production of
allelopathic chemicals.

A

Indirect competition

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47
Q

refers to the resumption of growth of the embryo in
the seed or of the young plantlet in the tuber, bulb, or rhizome.
* It marks the beginning of the battle for the survival of the weed.

A

Seed Germination

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48
Q

develops into the stem.

A
  • Plumule
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49
Q

stores or absorbs food
for the developing embryo.

A

Cotyledon:

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50
Q

first part of a seedling (a
growing plant embryo) to emerge
from the seed during the process
of germination – primitive root

A

Radicle:

51
Q

small pore on the seed
coat for absorption of water.

A

Micropyle

52
Q

outer seed coat, protective
layer

A
  • Testa:
53
Q

During germination, the cotyledons are raised above the ground
where they continue to provide nutritive support to the growing
points.
* This is the characteristics of bean seeds
* During the establishment, the hypocotyl begins to elongate in an arch
that breaks through the soil, pulling the cotyledon and the enclosed
plumule through the ground and projecting them into the air.
* Afterwards, the cotyledon open, plumule growth continues and the
cotyledon wither and fall to the ground

A

Epigeal germination

54
Q
  • The cotyledon remain below or at the surface of the ground as in grasses
    and sedges. In both species plumule is enclosed in the coleoptile.
  • The epicotyl is the rapidly elongating structure. The cotyledons provide a
    food source for the growing seedling, eventually shriveling up.
  • The first leaves are formed from the plumule and are sometimes referred
    to as ‘true leaves’. This characteristics of pea seeds and all grasses and as
    corn and many other species.
  • During germination, the cotyledons or comparable storage organs remain
    beneath the soil while the plumule pushes upward and emerges above the
    ground
A

Hypogeal germination

55
Q

absorption of water accompanied by swelling

A

Imbibition

56
Q

cell division and cell
elongation proceed at a fast rate supported by a rapid synthesis of
materials. The end result is the perceptive growth of the embryo.

A

Period of rapid metabolic activity

57
Q

– under field condition the radicle or root-like
structure break through the seeds and grow into the soil.

A

Emergence of root –

58
Q

commonly, this is considered the first
sign of weed growth, the shoot grows above the ground.

A

Emergence of the shoot

59
Q

the dependence on food reserve
ceases and the seedling start to manufacture its own
carbohydrate. From this stage on, the seedling is on its way to
establishment

A

Period of independent growth

60
Q
  • Seedling stage is the most important stage in weed establishment
  • It is the most sensitive stage to the environmental influences.
  • The demand for nutrients and water is high at this stage so that in a
    crop weed association the weed seedling competed strongly for these
    factors with the crop seedlings.
A

Seedling growth and development

61
Q
  • The most vulnerable and most practical stage for control.
  • The stage where damage against the crop is at the low level and any
    control measure can take advantage of the sensitivity of the weed
    seedling.
  • Most susceptible stage to herbicide action. The best time to apply
    pre-emergence herbicide.
  • Leaves at the early seedling stage are tender succulent, lack cutin and
    waxes allowing easy penetration of the herbicide.
  • Roots of seedlings have still thin epidermal walls making herbicide
    absorption more efficient.
A

Seedling stage

62
Q

seedling stage is characterized by rapid
metabolic activity which creates a big demand for the needed
soil resources. Most weeds are more efficient than crops in
drawing nutrients from the soil. Amaranthus accumulates
calcium, Cleome and Pistia accumulate potassium.

A

Nutrient level –

63
Q

salinization of areas near sea shore appear to favor
weeds than crop.

A

Salinity

64
Q

shading reduces the amount of light available to the plant
reducing photosynthetic activity and consequently reducing dry matter
production.

A

Light

65
Q

– the ability to adapt to adverse
conditions is responsible for the rapid spread and wide distribution of weeds.

A

Adaptation to growing condition

66
Q

most weeds derived their competitive
power from their rapid development manifested by: a. Rapid root growth and development
b. Rapid leaf production
c. Multiple shoot development
d. Formation of large and expansive foliar-type of cotyledon allowing early
photosynthetic function.
e. Formation of toxin, which may be toxic to other higher plants as in
Imperata and Rottboellia or toxic to microorganisms as in Tagetes erecta.

A

Competitive power of the weed

67
Q

It includes both detrimental and beneficial biochemical interactions
among all classes of plants, including microorganisms.

A

Allelopathy

68
Q

published a book on allelopathy. Defined as “any direct
or indirect harmful or beneficial by one plant (including
microorganisms) on another through the production of chemical
compounds that escape into the environment”

A

Rice (1984)

69
Q

Knotweed affect the wheat plant growth and development

A

Weed on Crop

70
Q

Imperata cylindrica (Cogon grass) inhibits the emergence and growth
of an annual broadleaf weed i.e. Borreria hispada (Button weed) by
exudation inhibitory substances through rhizomes.

A

Weed on Weed

71
Q

Oat, Pea, Wheat suppress the growth of Chenopodium album (lams
quarter)

A

Crop on Weed

72
Q

substance produced by a microorganism and effective
against another microorganism.

A

Antibiotic

73
Q

substance produced by a microorganism and toxic
against higher plants.

A

Marasmin -

74
Q
  • substance produced by a higher plant and effective
    against microorganism.
A

Phytoncide -

75
Q

substance produced by a higher plant and effective against
another higher plant.

A

Koline

76
Q
A
77
Q

– is the release of substances that
are toxic in the form in which they are produced in the
plant.

A

True allelopathy

78
Q

– is the release of substances
that are toxic or a result of transformation by
microorganism.

A

Functional allelopathy

79
Q

Ways of releasing Allelochemicals

A

Allelopathic chemicals are released from
plants as:
* Vapor – from root and leaf (through
stomata)
* Foliar
* Root
* Breakdown/decomposition of dead
plants
* Seed extract

80
Q

Factors affecting Allelopathic effect

A

Allelopathic effects might also depend on a number of other factors
that might be important in any given situation:
* Varieties
* Specificity
* Auto-toxicity
* Crop on crop effects
* Environmental factors

81
Q

Advantages of Allelopathy

A
  1. Limit competition for space, light,
    nutrients, water
  2. Autotoxicity (Chemical produced
    inhibits germination of its own seeds)
  3. Allelopathic weed suppression
    through the use of cover crops
82
Q

Crop allelopathy can be effectively
used to control weeds in the field.
* By intercropping those field crops
which can suppress weeds of next
crops.

A

Arrangement of cropping systems

83
Q
  • Allelopathic applications such as straw
    mulching, provide sustainable weed
    management
  • The allelochemicals from decomposed straw
    can suppress weed growth in farmlands, and
    reduce the incidence of pests and diseases.
A

Straw Mulching

84
Q
  • It is the inability if the seed or any vegetative propagule to germinate
    under favorable conditions.
  • It can be acquired as the seed or organ develops or matures (primary
    or natural dormancy) or
  • Induced through encounter with unfavorable conditions (induced or
    secondary dormancy)
A

Dormancy

85
Q

this involves the impermeability
of the thick seed coat to imbibe water and oxygen, hence even the
embryo is viable it will not germinate because of the barrier

A

Physical (Exogenous dormancy) –

86
Q

can be accounted to
immaturity of the embryo or to the presence of substances inhibitory
to the germination of weed seeds.
This type of dormancy is induced because of chemical changes within
the seed’s embryo.
One reason for a plant to not germinate during endogenous dormancy
is that the embryo is underdeveloped at maturity

A

Physiological (Endogenous dormancy)

87
Q

It is a condition when seeds cannot germinate
even when exposed to favorable growth conditions.
The inability is sometimes due to the embryo being immature at the
time of germination.
Innate dormancy can also be imposed chemically by inhibitory
compounds in the seed coat or the embry

A

Innate Dormancy

88
Q

Found when seeds are deprived of favorable
growth conditions such as sufficient moisture, oxygen, light, and
suitable temperature.
In enforced dormancy, no physiological mechanism is involved in
inducing dormancy.
The seeds are said to be in the ‘quiescent’ stage.

A

Enforced Dormancy -

89
Q

Caused by extremely unfavorable growth
conditions.
Such plant species have no innate dormancy but acquire them with
time.
After a certain period, the seeds permanently fail to germinate.

A

Induced Dormancy

90
Q

It is the process of removing the seed coat by
mechanically rupturing them. These make a hard seed coat
permeable to water and gases.

A

Scarification

91
Q

for a
short duration makes the seed coat soft, allowing water and oxygen
to enter.

A

Treating seeds with hot water or concentrated sulfuric acid

92
Q

Seeds of tobacco and tomato revokes dormancy
when exposed to white light after the seeds have imbibed 30-40%
moisture.

A

Exposure to white light

93
Q

Exposure to a very low intensity of light is sufficient
to overcome dormancy. Even a brief exposure to the red light of
wavelength 660u is effective for germination overcoming dormancy. In
contrast, exposure to far-red light of wavelength 730u induces dormancy
and thus prevents germination.

A

Exposure to red light

94
Q

Application of gibberellic acid
and kinetin can substitute to the red-light requirement of lettuce seeds.
Thus, seeds can germinate in the presence of these hormones in total
darkness.

A

Treatment with plant growth hormones

95
Q

Dormant seeds contain an inhibitory
hormone called gibberellic acid, which disappears during stratification. At
this point, gibberellic acid is secreted, which promotes seed germination.
Thus, the chilling requirement can be replaced through the application of
gibberellic acid.

A

Presence with gibberellic acid

96
Q

Chemicals such as potassium nitrate,
thiourea, and ethylene break seed dormancy and induces germination.
Similarly, the application of cytokinin and ethylene also promotes seed
germination.

A

Use of growth-promoting chemicals

97
Q

or approaches that reduce production and
germination of weed seeds and vegetative propagules and minimize
their establishment and spread.
* Use of high quality and disease and weed-seed free planting
materials.
* Control of weeds before they produce seeds or vegetative
propagules.

A

. Preventive Methods –

98
Q

directly destroy weeds or involve the
manipulation of the environment in the field to control weeds.

A

Physical/Cultural methods

99
Q

Initial plowing buries weeds
and stubbles from the previous crop, however, the process allows a
batch of weed seeds to germinate which is called a weed flush

A

Land preparation and management of weed seeds and vegetative
propagules reserve banks in the soil –

100
Q

weeds are controlled by uprooting or
with the use of various small local hand implements by slashing

A

Hand weeding/slashing –

101
Q

this method can be accomplished in less time
compared with uprooting the weeds

A

Hoe weeding

102
Q

directly destroy weeds or involve the
manipulation of the environment in the field to control weeds.

A

Physical/Cultural methods

103
Q

this may done with animal or tractor-drawn
implements

A

. Interrow cultivation

104
Q

provides considerable control of some weeds by
reducing light available to the crops and serving as a barrier to weed
emergence.

A

Mulching

105
Q

this method is effectively used in
transplanted lowland rice.

A

Water management or flooding

106
Q

– directly destroy weeds or involve the
manipulation of the environment in the field to control weeds.

A

Physical/Cultural methods

107
Q

a variety adapted to
the locality which is characterized by an early rapid growth provides
some measure of weed control through its competitive advantage.

A

Use of competitive crop varieties or cultivars

108
Q

this may involve spatial (intercropping) or
temporal (crop rotation or sequential cropping) combinations of crops
in an area in one year).

A

Multiple cropping

109
Q

– is the deliberate use of a weed’s natural
enemies, such as insects or pathogens to suppress the growth
or reduce the population of the weed. The types of biological
control are:

A

Biological control –

110
Q

use of host-specific damaging biotic
agents from the country of origin of the imported problem
weed species.

A

Classical approach

111
Q

this includes augmentation and
bioherbicide approaches.

A

Inundative approach

112
Q

– natural enemies already present
in the area where the problem weed species occur often
do not cause sufficient damage to effect adequate control
of the weeds because their population is low.

A

Augmentation approach

113
Q

involves the
application of inoculum of a weed pathogen in a manner
analogous to a chemical herbicide.

A

Bioherbicide / mycoherbicide approach

114
Q

Mycoherbicides——–are commercially
available for the control of specific weeds in the USA.

A

devine and colego

115
Q

involves the use of herbicides for selective
control of weeds with minimum or no injury to the crop
* The use of herbicides substantially reduces the labor requirement for
weed control and provides early season control of weeds within crop
rows.
* Safety precautions on the label should be strictly observed.
* Improper use of herbicides may result in crop injury, poor or
ineffective weed control and drift or residue problems.

A

. Chemical control –

116
Q

herbicide applied after land preparation
but before the crop is planted. The herbicide is volatile and
needs to be incorporated in the soil before planting. Examples
are fluchloralin, trifluralin, EPTC

A

Preplant herbicide

117
Q

the chemical is applied after the
crop is planted but before the weeds of the crop emerge.
Examples are pendimethalin, atrazine, alachlor, metolachlor,
butachlor, nitrofen, oxadiazon, clomazone, chlorimuron-p-ethyl

A

Preemergence herbicide

118
Q

– the herbicide is applied after the
crop or the weeds have emerged. Examples are 2,4-D,
butachlor, atrazine, isoproturon, fluazifop-p-butyl, fenoxapropp-ethyl, clodinafop-propargyl, chlorsulfuron, sulfosulfuron,
lactofen, tralkoxydim

A

Postemergence herbicide

119
Q

herbicide whose phytotoxic effects are
manifested at the sites of the plants where the spray droplets are
deposited. Examples: bromoxynil, ioxynil, paraquat, diquat, propanil

A

Contact herbicide

120
Q

erbicides whose phytotoxic
effects are manifested at and away from the sites on the plant
where the spray droplets are deposited. The herbicide is moved to
other parts of the plant. Examples: pendimethalin, trifluralin,
fluchloralin, 2,4-D, isoproturon, glyphosate, glufosinate-ammonium,
atrazine, metribuzin, nitrofen.

A

Translocated/Systemic herbicide

121
Q

herbicide that kills all
plants. Examples are Paraquat, glyphosate,
glufosinate-ammonium, acrolein, picloram, amitrole,
chlorfenac/fenac, metham, sodium chlorate.

A

Non-selective herbicides

122
Q

– herbicides that kill some plants
leaving others practically unharmed. All pre-planting,
pre-emergence and post emergence herbicides meant
for application in crops are selective ones.

A

Selective herbicides

123
Q

control a particular group of weeds like grasses,
broad-leaved or sedges. Their range of activity is narrow. Examples:
2,4-D, diclofop-methyl, flufenacet, fluazifop-p-butyl, fenoxaprop-pethyl, clodinafop-propargyl

A

Narrow spectrum

124
Q

control a wider array of weeds constituting
grasses, broad-leaved and/or sedges. Their range of activity over
the population of weeds is broad. Examples: metribuzin,
isoproturon, chlorsulfuron, atrazine, pendimethalin.

A

Broad spectrum –

CROP PROTECTION (4 decks)

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