Cultivation and collection of drugs of natural origin

CULTIVATION, COLLECTION, PROCESSING
AND STORAGE OF DRUGS OF NATURAL
ORIGIN

Introduction
• The crude drugs which reach the market and pharmaceutical
industries will have passed through different stages that have
some effect in the nature and amount of active constituents
responsible for therapeutic activity.
• Those stages are to be concerned more in order to make a drug
useful to the mankind by all means.
1. Cultivation
2. Collection
3. Drying
4. Garbling (dressing)
5. Packaging
6. Storage

Advantages of cultivation
• It ensures quality and purity of medicinal plants.
• If uniformity is maintained in all operations during the process of
cultivation, drugs of highest quality can be obtained.
• If the cultivated plants are kept free of weeds, the contamination of
crude drugs can be conveniently avoided.
• Collection of crude drugs from cultivated plants gives a better yield and
therapeutic quality.
• The cultivation of medicinal and aromatic plants also leads to
industrialization to a greater extent. The cultivation of coffee and cocoa
in Kerala has given rise to several cottage and small scale industries. The
cultivation of cinchona in West Bengal. The government owned opium
factory at Ghaziabad is an eloquent testimony to the significance of well
planned cultivation of Opium.
• Cultivation permits application of modern technological aspects such as
mutation, polyploidy and hybridization.

Disadvantages of cultivation :
• The losses occure due to natural calamities like storms,
earthquakes, flood, droughts, snowfall, tsunami etc.
• Cost of production of crude drugs is more as compared to that of
drugs collected from wild plants.
• Land, labour and money are required.

Methods of Plant Propagation
• Medicinal plants can be propagated by two usual methods as applicable
to nonmedicinal plants or crops.
• These methods are referred as sexual method and asexual method.
• Each of these methods has certain advantages, and also, disadvantages.
1. Sexual method of propagation :
• When the seed is used for rising seedling, the method is known as
sexual method of propagation.
• e.g. Acacia, cardamom, fennel. mustard etc.

• Advantages due to the sexual method of propagation :
• Seedlings are long-lived.
• Plants bear more and better fruits.
• Plants are more sturdy.
• Seedling are comparatively cheaper.
• Seedlings are easy to raise.
• In case of plants where other vegetative methods cannot be used,
propagation from seeds is the only methods of choice.
• It is very easy and economical for storage.
• It requires less cost.
• The seeds can easily be transported to any places.
• Very few days are required for raising seedlings.
• New variety can be produced easily by means of hybridization and
other methods.

Disadvantages due to sexual method of
propagation:
• Seedlings : Seedling - trees are not uniform in their growth
• They require more time to bear fruits, as compared to grafted plants.
• The cost of harvesting, spraying of pesticides etc. is more as compared
to grafted trees.
• Due to cross pollination the purity of the variety cannot be maintained.

II. Asexual Method of Propagation:
• When the vegetative part of the plant such as stem, root, or leaf etc. is
used in such an environment, that it develops into new plant, the
method of vegetative propagation is known as Asexual method of
propagation.
• e.g. Grapes, Pomegranate, Ginger and Turmeric.
• Advantages due to asexual method of propagation :
• There is no variation between the propagated plants and the mother
plants.
• Plants are uniform in growth, flowering, maturity and yielding capacity.
• Uniformity in case of quality of fruits makes the harvesting and
marketing easy.
• Seedless varieties of fruits can easily be propagated vegetatively. e.g.
Grapes.
• Plants start bearing earlier as compared with seedling trees.
• Budding or grating encourages disease resistant varieties of plants.

Disadvantages due to an Asexual method of propagation:
• In comparison to seedling trees, these are not vigorous in growth.
• They are not long lives.
• No new variety can be produced or evolved by this method
• Asexual method of vegetative propagation consists of three
types:
a) Natural methods of vegetative propagation
b) Artificial methods of vegetative propagation.
c) Aseptic method of micropropagation (tissue culture).

• Natural methods of vegetative propagation:
• It is done by sowing various parts of the plants in well prepared soil.
• The following are the examples of vegetative propagation:
• Bulbs: Squill, Garlic
• Tubers: Aconite, Jalap, Potato
• Rhizomes: Ginger, Turmeric
• Stolons: Liquorice
• Artificial methods of vegetative propagations:
• The method by which plantlets or seedlings are produced from
vegetative part of the plant by using some technique or process is
known as artificial method of vegetative propagation.
• These methods are classified as under –
• Cutting
• Layering
• Grafting

• Aseptic methods of micropropagation (tissue culture)
• It is a novel method for propagation of medicinal plants.
• In micropropagation, the plants are developed in an artificial medium
under aseptic conditions from fine pieces of plants like single cells,
callus, seeds, embryos, root tips, shoot tips, pollen grains, etc.
• They are also provided with nutritional and hormonal requirements.

Methods of Irrigation
• Water is essential for any type of cultivation.
• After studying the availably and requirement of water for a specific
crop, one has to design his own irrigation system at the reasonable cost.
• Following methods of irrigation :
1. Hand watering: economical and easy to operate.
2. Flood watering: easy to operate, results in wastage of water.
3. Boom watering: easy to operate, but restricted utility.
4. Drip irrigation: Scientific, systematic and easy to operate; costly.
5. Sprinkler irrigation: Costly, gives good results.

Cultivation and collection of drugs of natural origin

Collection of crude drugs
• Collection is the most important step which comes after cultivation.
• Drugs are collected from wild or cultivated plants and the tasks for
collection depends upon the collector, whether he is a skilled or
unskilled.
• Drugs should be collected when they contain maximum amount of
constituents in a highly scientific manner.
• The season at which each drug is collected is so important, as the
amount, and sometimes the nature, of the active constituents could be
changed throughout the year.
• For example, Rhubarb is collected only in summer seasons because no
anthraquinone derivatives would be present in winter season but
anthranols are converted to anthraquinones during summer.
• Not only the season but also the age of the plant should be taken in to
great consideration since it governs not only the total amount of active
constituents produced in the plants but also the proportions of the
constituents of the active mixture.
• Reduction in the percentage of alkaloids in datura as the plant ages are
examples of the effect of aging in plants

• Moreover the composition of a number of secondary plant metabolites
varies throughout the day and night, and it is believed that some inter
conversion would happen during day and night.
• Generally the leaves are collected just before the flowering season, e.g.
vasaka, digitalis, etc., at this time it is assumed that the whole plant has
come to a healthy state and contain an optimum amount of
metabolites.
• Underground organs collected as the aerial parts of plant cells die, e.g.
liquorice, rauwolfia, etc
• Some fruits are collected after their full maturity while the others are
collected after the fruits are ripe.
• Barks are usually collected in spring season, as they are easy to
separate from the wood during this season.
• The barks are collected using three techniques
• felling (bark is peeled off after cutting the tree at base),
• uprooting (the underground roots are dug out and barks are collected
from branches and roots)
• coppicing (plant is cut one meter above the ground level and barks are
removed).

• Underground parts should be collected and shaken, dusted in order to
remove the adhered soil, water washing could be done if the adhered
particles are too sticky with plant parts.
• The unorganized drugs should be collected from plants as soon as they
comes out, e.g. resins, latex, gums, etc.
• Discoloured drugs or drugs which were affected by insects should be
rejected

Drying of crude drugs :
• Before marketing a crude drug, it is necessary to process it properly, so
as to preserve it for a longer time and also to acquire better
pharmaceutical elegance.
• This processing includes several operations or treatments, depending
upon the source of the crude drug (animal or plant) and its chemical
nature.
• Drying consists of removal of sufficient moisture content of crude drug,
so as to improve its quality and make it resistant to the growth of
microorganisms.
• Drying inhibits partially enzymatic reactions.
• Drying also facilitates pulverizing or grinding of a crude drug.
• In certain drugs, some special methods are required to be followed to
attain specific standards, The slicing and cutting into smaller pieces is
done to enhance drying, as in case of glycyrrhiza,
• The flowers are dried in shade so as to retain their colour and volatile
oil content.

• Depending upon the type of chemical constituents, a method of drying
can be used for a crude drug.
• Drying can be of two types (1) natural (sun drying) and (2) artificial.
1. Natural Drying (Sun Drying)
• In case of natural drying, it may be either direct sun drying or in the
shade.
• If the natural colour of the drug (digitalis, clove, senna) and the volatile
principles of the drug (peppermint) are to be retained, drying in shade
is preferred.
• If the contents of the drugs are quite stable to the temperature and
sunlight, the drugs can be dried directly in sunshine (gum acacia, seeds
and fruits)

2. Artificial Drying
• Drying by artificial means includes drying the drugs in
• (a) an oven; i.e. tray dryers
• (b) vacuum dryers and
• (c) spray dryers.
• a. Tray dryers
• The drugs which do not contain volatile oils and are quite stable to heat
or which need deactivation of enzymes are dried in tray dryers.
• In this process, hot air of the desired temperature is circulated through
the dryers and this facilitates the removal of water content of the drugs
(belladonna roots, cinchona bark, tea and raspberry leaves and gums
are dried by this method).

• b. Vacuum dryers
• The drugs which are sensitive to higher temperature are dried by this
process, e.g. Tannic acid and digitalis leaves.
• c. Spray dryers
• Few drugs which are highly sensitive to atmospheric conditions and
also to temperature of oven drying are dried by spray drying method.
• The technique is followed for quick drying of economically important
plant or animal constituents, rather than the crude drugs.
• Examples of spray drying are papaya latex, pectin, tannins, etc.
• Expensive method compare to natural drying and oven drying.

GARBLING (DRESSING)
• The next step in preparation of crude drug for market after drying is
garbling.
• This process is desired when sand, dirt and foreign organic parts of the
same plant, not constituting drug are required to be removed.
• This foreign organic matter (extraneous matter) is removed by several
ways and means available and practicable at the site of the preparation
of the drugs.
• Excessive stems in case of lobelia and stramonium need to be removed,
while the stalks, in case of cloves are to be deleted.
• Drugs constituting rhizomes need to be separated carefully from roots
and rootlets and also stem bases.
• Pieces of iron must be removed with the magnet in case of castor seeds
before crushing and by shifting in case of vinca and senna leaves.
• Pieces of bark should be removed by peeling as in gum acacia.

PACKING OF CRUDE DRUGS
• The morphological and chemical nature of drug, its ultimate use and
effects of climatic conditions during transportation and storage should
be taken into consideration while packing the drugs.
• Aloe is packed in goat skin.
• Colophony and balsam of tolu are packed in kerosene tins, while
asafoetida is stored in well closed containers to prevent loss of volatile
oil.
• Cod liver oil, being sensitive to sunlight, should be stored in such
containers, which will not have effect of sunlight,
• the leaf drugs like senna, vinca and others are pressed and baled.
• The drugs which are very sensitive to moisture and also costly at the
same time need special attention, e.g. digitalis, ergot and squill.
• Squill becomes flexible; ergot becomes susceptible to the microbial
growth, while digitalis looses its potency due to decomposition of
glycosides, if brought in contact with excess of moisture during storage.

• Hence, the chemicals which absorb excessive moisture (desiccating
agents) from the drug are incorporated in the containers.
• Cinnamon bark, which is available in the form of quills, is packed one
inside the other quill, so as to facilitate transport and to prevent
volatilization of oil from the drug.
• The crude drugs like roots, seeds and others do not need special
attention and are packed in gunny bags, while in some cases bags are
coated with polythene internally.
• The weight of certain drugs in lots is also kept constant.

STORAGE OF CRUDE DRUGS
• A good quality of the drugs can be maintained, if they are preserved
properly.
• All the drugs should be preserved in well closed and, possibly in the
filled containers.
• They should be stored in the premises which are waterproof, fire proof
and rodentproof.
• A number of drugs absorb moisture during their storage and become
susceptible to the microbial growth.
• Some drugs absorb moisture to the extent of 25% of their weight.
• The moisture, not only increases the bulk of the drug, but also causes
impairment in the quality of crude drug.
• The excessive moisture facilitates enzymatic reactions resulting in
decomposition of active constituents e.g. digitalis leaves and wild
cherry bark.
• Gentian and ergot receive mould infestation due to excessive moisture

• Radiation due to direct sunlight also causes destruction of active
chemical constituents, e.g. ergot, cod liver oil and digitalis.
• Form or shape of the drug also plays very important role in preserving
the crude drugs.
• Colophony in the entire form (big masses) is preserved nicely, but if
stored in powdered form, it gets oxidized or looses solubility in
petroleum ether.
• Squill, when stored in powdered form becomes hygroscopic and forms
rubbery mass on prolonged exposure to air.
• The fixed oil in the powdered ergot becomes rancid on storage.
• Atmospheric oxygen is also destructive to several drugs and hence, they
are filled completely in well closed containers, or the air in the container
is replaced by an inert gas like nitrogen; e.g. shark liver oil, papain, etc.

• Apart from protection against adverse physical and chemical changes,
the preservation against insect or mould attacks is also important.
• They can be prevented by drying the drug thoroughly before storage
and also by giving treatment of fumigants.
• The common fumigants used for storage of crude drugs are methyl
bromide, carbon disulphide and hydrocyanic acid.
• Temperature is also very important factor in preservation of the drugs,
as it accelerates several chemical reactions leading to decomposition of
the constituents.
• Hence, most of the drugs need to be preserved at a very low
temperature.
• The costly phytopharmaceuticals are required to be preserved at
refrigerated temperature in well closed containers.
• Small quantities of crude drugs could be readily stored in airtight,
moisture proof and light proof containers such as tin, cans, covered
metal tins, or amber glass containers.
• Wooden boxes and paper bags should not be used for storage of crude
drugs

FACTORS AFFECTING CULTIVATION AND
COLLECTION OF DRUGS FROM NATURAL
ORIGIN

• Cultivation of medicinal plants offers wide range of advantages over the
plants obtained from wild sources.
• There are few factors to concern which have a real effect on plant
growth and development, quality and quantity of secondary
metabolites.
• Nutrients have the ability to enhance the production of secondary
metabolites, at the same time they may reduce the metabolites as well.
• The factors affecting cultivation are -
1. Altitude
2. Temperature
3. Rainfall
4. Length of day
5. Day light
6. Soil
7. Soil fertility
8. Fertilizers and Manures
9. Pest and pest control

1. Altitude
• Altitude is a very important factor in cultivation of medicinal plants.
• Tea, cinchona and eucalyptus are cultivated favourably at an altitude of
1,000–2,000 meters.
• Cinnamon and cardamom are grown at a height of 500–1000 meters,
while senna can be cultivated at sea level.
• The following are the examples of medicinal and aromatic plants
indicating the altitude for their successful cultivation.

2. Temperature :
• Temperature is a crucial factor controlling the growth and metabolism
and there by the yield of secondary metabolites of plants.
• Even though each species has become adapted to its own natural
environment, they are able to exist in a considerable range of
temperature.
• Many plants will grow better in temperate regions during summer like
sesame seeds, and many plants grow better in winter like coriander,
cumin, wheat, etc.

3. Rainfall :
• For the proper development of plant, rainfall is required in proper
measurements.
• Xerophytic plants like aloes do not require irrigation or rainfall.
• The effects of rainfall on plants must be considered in relation to the
annual rainfall throughout the year with the water holding properties of
the soil.
• Variable results have been reported for the production of constituents
under different conditions of rainfall.
• Excessive rainfall could cause a reduction in the secondary metabolites
due to loss of water soluble substances from the plants.

4. Day length and light :
• It has been proved that even the length of the day has an effect over the
metabolites production.
• The plants that are kept in long day conditions may contain more or less
amount of constituents when compared to the plants kept in short day.
• For example peppermint has produced menthone, menthol and traces
of menthofuran in long day conditions and only menthofuran in short
day condition.
• The developments of plants depends upon both the amount and
intensity of the light they require.
• The wild grown plants would meet the required conditions and so they
grow but during cultivation we have to fulfill the requirements of plants.
• The day light was found to increase the amount of alkaloids in
belladonna, stramonium, cinchona, etc.

5. Soil
• Each and every plant species have its own soil and nutritive
requirements.
• The three important basic characteristics of soils are their physical,
chemical and microbiological properties.
• Soil provides mechanical support, water and essential foods for the
development of plants.
• Soil consists of air, water, mineral matters and organic matters.
• Variations in particle size result in different soils ranging from clay, sand
and gravel.
• Particle size influences the water holding capacity of soil.
• The type and amount of minerals plays a vital role in plant cultivation.
• Calcium favours the growth of certain plants.
• Nitrogen containing soil has a great momentum in raising the
production of alkaloids in some plants.

• Depending upon the size of the mineral matter, the following
names are given to the soil
Depending upon the percentage of clay, soils are classified as under

• pH of the soil:
• pH is the hydrogen ion concentration i.e. pH is defined as the negative
logarithm to base of the hydrogen ion concentration.
• In pure water, the concentrations of both ions are equal.
• The pH of the soil indicates favourable growth of plants & presence of
microorganisms.
• The maximum availability of plant nutrients is in between the pH
range 6.5 to 7.5.
• An acidic soils are not suitable for leguminous crops due to poor
development of nodular bacteria.
• Some of the plants like tobacco, tea, cinchona, potato grow well only in
acidic soil.
• The acidic pH is disadvantageous as it solubilize more iron.
• Groundnut, cotton, sunflower grow better in alkaline soils.
• In alkaline soils, phosphorous is converted to insoluble forms of
calcium phosphate & so it is not available to the plants.

6. Soil fertility :
• It is the capacity of soil to provide nutrients in adequate amounts and
in balanced proportion to plants.
• If cultivation is done without fertilizing soil with nutrients, soil fertility
gets lost.
• It is also diminished through leaching and erosion.
• Soil fertility can be maintained by addition of animal manures,
nitrogen-fixing bacteria or by application of chemical fertilizers.
• Soil fertility can be maintained as under:
1. By addition of farm yard manure, compost , other organic manures
like bone meal, fish meal, blood meal, press-mud, different cakes i.e.
Groundnut cake, castor cake, karanj cake & other organic materials to
the soil & enrich the soil fertility.
2. Crop rotation with leguminous crops is followed as the leguminous
crops fix the nitrogen from air by means of nitrogen fixing bacteria.
3. Chemical fertilizer can be applied to soil in less quantity.

4. Proper drainage for removing excess water are prepared horizontally
to slope of the soil of field & to slope of the soil or field & to avoid
leaching of the nutrients from oil.
5. Soil conservation is done by putting bunds horizontal to slope to
avoid erosion of soil.
6. Biofertilizer are added to the soil to enrich the soil fertility.
7. Seed treatment with proper biofertilizer is done to increase nitrogen
level in the soil.
8. Micro nutrients are added to the soil according to the requirement of
land to maintain the fertility.
9. Soil corrector such as lime is added to maintain the acidic condition &
the alkaline soils can be reclaimed by application of the gypsum to
the soil, to maintain the fertility of the soil.

7. Fertilizers and manures :
• Plants need food for their growth and development.
• Basically plants need for their growth are the carbon dioxide(CO2), sun
rays, water and mineral matter from soil.
• With the limited number of chemical elements, plants build up, fruits,
grains, fibers etc. and synthesize fixed oil and volatile oils, glucosides,
alkaloids, sugar and many other chemicals.
• The chemical elements or their compounds used for plant growth are
known as fertilizers.
• e.g. Urea, muriate of potash, Diammonium phosphate.

Chemical fertilizers and micronutrients :
• plants are in need of 16 nutrient elements for synthesizing various
compounds.
• Some of them are required in large amount known as primary nutrients
like nitrogen, phosphorus and potassium.
• Some of them are required in small quantities and hence, they are
known as secondary nutrients like Magnesium, calcium and Sulphur
• Other are required in very small quantity, known as Trace elements like
copper, manganese, iron, boron, molybdenum, zinc.
• Carbon, hydrogen, oxygen and chlorine are provided from water and
air.
• Every element has to perform some specific function in growth and
development of plants.
• Its deficiency is also characterized by certain symptoms.

1. Nitrogen is needed for the production and the development of
vegetative growth of the plant. The deficiency of nitrogen is indicated
by the yellowing of leaves of the plant.
2. Phosphorous is useful for producing fruits and sugar development in
the fruits. It speed up maturity and ripening of fruits. Radish, beet,
potato require more phosphorous for their development.
3. Potassium produces sturdiness in the plants. It acts as a catalytic
agent in the synthesis of the carbohydrates and proteins. Deficiency
of potassium is observed, as stem becomes slender and leaves
colourless.
4. To avoid deficiency some of the nutrients are given into soil or
spraying is done of the same on the medicinal plants

• Inorganic fertilizers are known as chemical fertilizers.
• They are prepared in the factory by certain chemical process or found
in the soil and processed in the factory.
• They are of different types such as :
1. Straight fertilizers: Each straight fertilizer consists of only one element
useful for plant.
i. Nitrogenous fertilizers: They content only nitrogen which is useful for
plant growth. e.g. Urea 46% N, Ammonium sulphate 20.5% N,
Calcium Ammonium Nitrate 6%N.
ii. Phosphorous fertilizers: They supply P2O5 to the plants. e.g. Single
supper phosphate 16% P2O5 , Double supper phosphate 32% P,
iii. Potassium fertilizers: The plants absorb K2O from these fertilizers.
e.g. Muriate of potash 58% K.
2. Compound fertilizers: They are chemical compounds having more
than one i.e. two or more elements - N, P or K. e.g. Diammonium
phosphate (DAP) 18% N and 46% P.
3. Mixed fertilizers :
• They are prepared in the factory by mixing straight or compound
fertilizers in a certain proportion for particular group of crops.

Manures :
• the waste matter from animals or plants that is put on the ground in
order to make plants grow better
• Farm yard manure (FYM/compost), castor seed cake, poultry manures,
neem and karanj seed cakes vermin compost, etc. are manures.
• Oil-cake and compost normally consists of 3–6% of nitrogen, 2% phosphates
and 1–1.5% potash.
• They are made easily available to plants. Bone meal, fish meal, biogas slurry,
blood meal and press mud are the other forms of organic fertilizers.
Biofertilizers
• Inadequate supply, high costs and undesirable effects if used successively
are the demerits of chemical fertilizers and hence the cultivator has to opt
for some other type of fertilizer.
• Biofertilizers consist of different types of micro organisms or lower
organisms which fix the atmospheric nitrogen in soil and plant can use
them for their day to day use.
• Thus they are symbiotic in nature.
• Rhizobium, Azotobacter, Azospirillium, Blue-green algae, Azolla, etc. are the
examples of biofertilizers.
• The seed is treated with biofertilizers before sowing.
• The rate of application of 250 gms of biofertilizer is treated with 10 kg of
seeds

8. Pest and pest control
• Pests are undesired plant or animal species that causes a great damage
to the plants.
• There are different types of pests -
1. Microbes
2. Insects
3. non insect pests
4. weeds.

 MICROBES :
• They include fungi, bacteria and viruses.
• Armillaria Root Rot (Oak Root Fungus) is a disease caused by fungi
Armillaria mellea (Marasmiaceae) and in this the infected plant become
nonproductive and very frequently dies within two to four years. Plants
develop weak, shorter shoots as they are infected by the pathogen
• Xylella fastidiosa is a bacterium causes Pierce’s Disease, in this leaves
become slightly yellow or red along margins and eventually leaf margins
dry or die.
• Many viruses are also reported to cause necrosis of leaves, petioles and
stems, they are tobacco mosaic virus, mosaic virus, cucumber mosaic
virus, tobacco ring spot virus, yellow vein mosaic, etc.
Controlling techniques:
• Chemical fumigation of the soil, fungicide, bactericide, pruning, proper
water and fertilizer management, good sanitation, heat treatment of
planting stock, cut and remove the infected parts, genetically
manipulating the plants for producing plants to resist fungi and bacteria
are practices that are used to prevent or minimize the effects produced
by microbes.

INSECTS :
• Ants, they are of different varieties, Argentine ant, Gray ants, Southern
fire ant, Thief ant.
• They spoil the soil by making nest.
• Leafhoppers remove the contents of leaf cells, leaving behind empty
cells that appear as pale yellow spots.
Controlling techniques:
• Tilling (mechanical agitation)the soil will also affects the nesting sites of
ants and help to reduce their populations, collection and destruction of
eggs, larvae.
• trapping the insects
• Use of insecticides

NON INSECT PESTS :
• They are divided in to vertebrates and invertebrates.
• Vertebrates that disrupt the plants are monkeys, rats, birds, squirrels,
etc.
• Non vertebrates are, Web spinning Spider Mites causes discoloration in
leaves and yellow spots, as they feed leaf contents out of leaf cells.
• Nematodes produces giant cell formation, disturbs the uptake of
nutrients and water, and interferes with plant growth.
Controlling techniques :
• Construction of concrete ware houses,
• traps,
• Use of rodenticides, etc.

WEEDS :
• A weed is unwanted plant in the cultivated field.
• The losses due to weeds are very heavy.
• Weeds lead to loss of nutrients, water, light, space and they make
composition with the cultivated plants.
• They increase labour cost and equipment.
• They cause less and low product quality and problems in marketing.
• They enhance changes for attacks of bacteria, fungi, viruses, and insect.
• The losses of nutrients and moistures, due to weeds are the problems in
the food crops, medicinal and fiber crops.
• Controlling techniques :
• Use of low rates of herbicides
• Herbicides are traditionally discussed as two groups –
• those that are active against germinating weed seeds (pre-emergent
herbicides) and
• those that are active on growing plants (post-emergent herbicides).
• Some herbicides have both pre-and post-emergent activity

General Methods of Pest Controls

Other Factors that Affect the Cultivated Plants
Air Pollution
• Chemical discharges into the atmosphere have increased dramatically
during this century, but the total effect on plants is virtually unknown.
• It has been demonstrated that air pollutants can cause mortality and
losses in growth of plants.
• Nearly all species of deciduous and coniferous trees are sensitive to
some pollutants.
Herbicide
• Herbicides should be handled very carefully
• misapplication of herbicides can often damage nontarget plants.
• Symptoms of herbicide injury are variable due to chemical mode of
action, dosage, duration of exposure, plant species, and environmental
conditions.

Cultivation and collection of drugs of natural origin

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