In the economic field Japan continues to be a major
trade partner of Pakistan
Feb-11 - 17, 2002
Basically, Pakistan is an agricultural country and
therefore, all roads to the nation's socio-economic progress and
prosperity lead through a modernizing agricultural and a concurrent
effort at industrializing particularly based on the home grown raw
materials. Being the dominant sector of the economy, agriculture
contributes 25% to gross domestic product (GDP), employees 44% of
country's working force and contributes substantially to export
earnings. Major crops such as, wheat, rice, cotton and sugarcane
account for nearly 89% of value added in major crops. The value added
in major crops accounts for 41% of value added in overall agriculture.
Thus, these four major crops, on an average, contribute 36.5% to the
value added in agriculture. While, the minor crops such as pulses,
potato, vegetables, fruits etc. account for 10% of value added.
Our major objectives are to increase the
production, either by increase in areas or productivity. Acreage
increase has limitations like scarcity of water and precariously
established balance in land allocation between equally important cash
crops. Any disturbance in this balance may cause another crisis, more
or less of equal severity. Hence, productivity enhancement along with
pre and post harvest losses management are the only alternative and is
viable meaningfully, because of the existing differential between the
national average and the potential. The low national average is due to
the fact, that three-fourth of the farmers do not use proper
technological management in adequate quantity and proper combination
of local available resources.
Wheat (Triticum aestivum L.) belongs to the
Gramineae family. In Pakistan wheat is the most important food crop.
The largest cropped area is devoted to wheat, which is about 8.5
million hectares and the quantity produced is more than that of 2.9%
to GDP. The unprecedented drought conditions in the country have
severely affected the wheat crop. Firstly, the area under the crop
declined by 3.8% from 8463 thousand hectares to 8137 thousand hectares
in the year 2000-2001. Secondly, according to the preliminary
estimates, the size of wheat crop is 12.1% lower than the last year,
declining from 21.079 to 18.535 million tons. The area, production and
yield are 8306.6 thousand hectares, 18237.6 thousand tons, and 2196.0
thousand kg per hectare, respectively. On the other hand, its
procurements, releases and stocks are 8582.0, 5537.0 and 3526.0
thousand tons, respectively.
Losses in wheat
Wheat is adapted to temperate regions, receiving
annual rainfall of about 500-1200 mm. Higher precipitation causes
lodging and diseases and interferes with field operations of planting
and harvesting, so the yield is reduced. In rainfed areas, if rainfall
occurs early, wheat can be planted in the last fortnight of October.
Late planting of wheat can be done up to the middle of December, after
which further delay in sowing reduced yield drastically. Wheat sowing
however, after 20th November can cause a reduction of 15-20 kg per
acre yield during each subsequent day. There are two critical periods,
during which water stress reduces yield greatly; the period from the
development of adventitious roots to the start of tillering, and the
period from anthesis to the milk stage. According to an estimate the
presence of weeds in wheat fields can reduce 14-42% of the produce.
Thus, if 40 maunds of grains per acre are expected, it will reduce up
to 23 maunds only. Seed rate for early, medium and late sowing
varieties, should be 50, 60 & 70 kg/acre and any change in the
seed rate causes substantial yield losses. Nitrogen and phosphorus
fertilizers using ratio should be 1.5:1. Crops sown after rice and
sugarcane or through tubewell irrigated or sandy areas should be
supplied with one bag of potash per acre, otherwise yield will
adversely be affected.
Wheat crop is damaged by a large number of insects
such as grasshoppers, crickets, aphids, army worms, while standing in
the field. Grasshoppers and white ants attack plants during the
seedling stage, they are more serious in rainfed areas. Aphids and
army worms attack the crop in spring after heading, causing a
considerable losses while the crop is still standing in the field.
These pests also eat away the ears, including awns, immature grains,
tillers, tender leaves in the central whorl of the plant and even the
older leaves. Rodents cause little damage to the seedling and most of
the damage is caused at the ripening stage. Early and late wheat crop
is more liable to damage by birds. They eat the seeds before emergence
or soon after emergence at planting season. Birds also damage the crop
after the dough stage by eating the grain directly from the spikes and
by causing some years to shatter completely.
Wheat is also attacked by a number of diseases that
cause great losses to the quantity and quality of the produce. Rusts,
smuts, powdery mildew and septoria are important diseases that reduce
the yield of wheat in different parts of Pakistan. Powdery mildew
sometimes attacks wheat in mountainous and sub- mountainous regions.
Nematodes also infest wheat, in case of severe infestation, the
seedlings may fail to come out of the soil, even if they grow, the
infested plants remain stunted and give a shriveled unhealthy
appearance. A variable number of grains in an infested earhead may
produce galls, which are shorter and thicker than the healthy ones.
Although, they cause little mechanical injury to the plant root, yet
their presence stimulate the formation of branched rootlets. The main
root remains shorter or bunchy, bearing small galls.
In areas, where termites or weevils impose economic
problems, the crop should be sown after mixing granular insecticides
with soil. If the attack of insects persists, the insecticides can be
dusted on the crop. In certain fields, where heavy doses of N and P
are applied year after year, symptoms of zinc deficiency may be noted.
These symptoms appear on leaves as small white irregular patches.
Rodents and birds damage can be reduced to greater extent by the
presence of alternative crops, lack of shelter, scaring devices and
poison baits. To avoid damage from diseases, resistant varieties of
wheat should be grown, seed treatment can also be effective. Nematodes
can be controlled by a suitable crop rotation. Gall nematodes can be
controlled by separating the galls from the wheat seed by floating
them on water in a tub.
Post harvest technology for wheat crop
A plentiful harvest of wheat is only achieved, when
all necessary inputs are put together with appropriate production
technology. It has been observed that majority of the farmers
including progressive growers, who take keen interest in growing high
yielding varieties and adopt high production technology right from
selection of soil to the harvest of crop, ignore losses those occur
at, and after harvesting of the crop. Both wheat grain and straw have
tremendous economic value, and is consumed with great desire by men,
animals and birds. Some losses at post harvest levels are discussed
i) Shattering: Shattering of grains from the
arched occurs in the shattering susceptible varieties, before and
after harvesting in the field. Substantial losses also occur during
lying of wheat bundles and transportation from field to the threshing
yard. The cultivation of shattering resistant varieties can be helpful
in reducing these losses.
ii) Over-drying: Over-drying of the harvested
crops in the field, results in shattering and damage by rodents,
birds, animals and sometimes by dispersing wind. It is recommended
that the crops should be heaped after proper drying in the threshing
iii) Delayed threshing: Light to heavy losses
may occur, if threshing is delayed. Untimely rains and fast winds may
cause severe losses. It is recommended that threshing should be
carried out without any delay. While, heaping the materials in
threshing yard, it is recommended that earheads should face the centre,
so as to prevent losses from periphery damage by animals etc.
iv) Improper threshing yards: Improper
threshing yard is also responsible for the deterioration of grain and
straw quality and losses in productivity. It is recommended that the
threshing yard, if not cemented should be at least clean thoroughly,
even and free from soil cracks.
Losses during threshing: Losses may occur
during threshing, if a) the crop at the time of heaping was not dried
properly, b) the functioning of thresher is not proper, c). the
inadequate skill of the thrasher operator, d) the wind velocity and
direction of the thresher are not proper;
It is recommended that to avoid losses in
threshing, due consideration should be given~on the quality of
thresher, skillness of the operator, wind velocity etc. Delayed
threshing may result into, a) damage by rodents, white ants, birds and
animals, b) damage by rains and wind, c) Insecurity from fire and
occasional flood etc.
It is recommended that crop after harvesting should
be heaped in threshing yard and the process of threshing be completed
at the earliest. Losses may occur during bagging, if the quality of
bags is not maintained. It is recommended that new gunny bags should
be used, and if such bags are not available, then gunny bags in good
conditions be used. In that condition, bags may be cleaned thoroughly
for other seeds inside to avoid impurities and mixture. It is
recommended that bags may be treated with some insecticides such as
Malathion to get rid of residues of stored grain pests.
Wheat is to be stored by the producers, farmers and
consumers in their homes and by the traders and official agencies in
godowns. When this crop is harvested in the field, it is practically
free from pest infestation. Grain often infested during the process of
transportation, processing and storing. As a pests of this grain,
rodents (rats, mice), birds (especially sparrows) and insects are
worth mentioning. Rodents including rats, mice and moles are
responsible for causing enormous losses to the stored grains and
besides feeding, they destroy a substantial quantity by spillage and
contamination with their droppings, urine and body hairs. A rat is
estimated to consume about 27 grams of grain daily; in this way they
consume several million tons of wheat grain annually.
Sparrow, parakeet, crow, myna and pigeon are
destructive and cause much damage by feeding and by causing the grains
to shed in the storage. They also visit the thrashing-floors to feed
and use up quite large quantity of wheat.
At the time of harvest, wheat grains should be
dried to have their moisture contents less than 9 %, which is ideal
for storage. Grains kept in damp godowns, absorb moisture from ground
or atmosphere. The warm season and high moisture content of grain are
highly conducive to proper development and multiplication of insect
pests of stored wheat. The insects reach the grains either through the
infested gunny bags, receptacles or through the storage of fresh
grains in godowns already having infested grains. Within one season,
they may destroy 10-15 % of the grains and contaminate the rest with
undesirable odours and flavours. There are 4 insects viz., the meal
moth, grain moth, rice moth and almond moth belonging to order
Lepidoptera; Khapra beetle, red flour beetle, grain borer, gram dhora,
mung dhora and rice weevil in the order Coleoptera and mites in the
The damage caused by these pests is the greatest
during the monsoon season, when it is hot and humid. Only the larvae
of these insects, cause damage by feeding on the grain kernels. The
adults are active creatures, capable of short flights and fly about
from one bin to another and spread infestation all around. Larval
stages bore into the grain and feed on its contents, and about 30-50%
of the contents are consumed. If infestation is severe, the
devastation is completed, reducing the grain to a mere frass, the
grains give out an unpleasant smell and present sickly appearance.
Infested grains converted into flour have a characteristic off foul
As a result of destructive activities of stored
grain mites, the capacity of wheat to germinate is lowered up to 54%.
The most notable result is reduction in protein content. Mites raise
moisture contents of the grain generating sufficient heat for the
growth of infectious bacteria and fungi. They contaminate the space
between the grains with their dead bodies, cast skins and excrement,
thereby hindering the circulation of air in the stock. Flour prepared
from such contaminated grains has higher moisture contents, higher
acidity and tends to stick together in addition to being cause of
diseases. Such wheat flour has fusty smell, bitter taste and
deteriorated baking quality.
Control of stored grain pests
Pakistani farmers are very hard working, they are
busy all the time in growing tons of grains and fiber in adverse
climatic conditions of heat and cold, but unfortunately still, we are
not self sufficient in food even. Is it the fault of fortune? No.
There are many factors responsible for it to which we are not paying
attention. Among these factors non-availability of proper storage
conditions is of prime importance.
Losses in storing: Improper storing results in
It is recommended that wheat grain should not have
the moisture content higher than 9-12%.
a) the wheat should be stored at some elevated
b) the store should have adequate air and sun light
c) the store should be cleaned and treated with
some chemicals to avoid insect pest attack,
d) the store should not have the entrance place for
foreign animals such as dogs, cats, birds, rodents etc. as that may
spoil the quality and quantity of the stored grain,
e) Gunny bags in the store be placed systematically
f) After rainy season, the store should be
fumigated and if possible, the grain may be sun dried to maintain the
g) and overall a continuous regular periodical
examination of the store and grain is required.
Bhusa or straw is not less important than grain,
care must be taken for its proper storage.
There are several methods to control stored grain
pests, helping to check the spread of harmful insects and mites to
markedly reduce their potential of infestation.
Some dangerous pests enter in the country alongwith
seed and food grain imported from other cauntries. So, quarantine
measures towards preventing the import of foreign pests should be very
strict. The material to be imported should be subjected to laboratory
test to detect any kind of pests at the point of entry.
2. Sanitation of stores
Stores should be cleaned. All cracks, holes,
crevices etc. should be properly sealed. All granaries, machines and
grounds of enterprises must be completely disinfected. All the post
harvest wastes should be burnt or buried in soil.
3. Chemical control
Contact pesticides are commonly used on the surface
of the floor of stores as dust or emulsion. Fumigants are generally
used in hermetically sealed places. They are highly effective, if the
necessary concentration is maintained over the required period of
time. Among the various methods of controlling stored grain pests,
most widely used are chemical methods.
4. Biological control
Lepidopterous pests of wheat can be controlled
through natural enemies. Predaceous mites and parasites can control
the stored wheat pests e.g. Trichogramma, can control the
Angoumois grain moth successfully. In NIA, Tandojam, a biocontrol
laboratory is rearing this parasite, but no regular experimentation
has been carried out due to lack of manpower and facilities. Certain
predatory mites, Ichneumonids, brachonid, chalcid, protozons and
microbes act as predators and parasites of stored grain pests.
5. Resistant varieties
Research observations have shown that some
varieties of different agricultural crops have grain resistant to
insect pest attack. Such stock of resistant cultivars may be used to
raise the varieties, highly resistant to the stored grain pest
6. Radiation control
Ionizing radiations have been used by the scientist
to disinfest various stored items. Gamma radiation, X-rays, Cobalt and
Cesium can be used to combat the storage pests.
7. Use of heat and cold environments
Temperature of 140°F, given for 10 minutes is
lethal to most of the stored grain pests. Many insects are inactive
below 50°F, grain stored from 40 to 50°F can escape insect
infestation. Special precautionary measures should be adopted when
grains are kept under temperature treatments as they are deteriorated
For the control of bird pests of stored grain,
measures should be taken to deprive them of their food and nesting
places. For this purpose, covering windows and doors with wire screen,
sealing holes & crevices, construction of granaries and warehouses
in a way that there is no gap between walls where the birds could nest
and rest, are of great importance.
Rodent pest can be exterminated by keeping the
grain and grain products dry, rodents should be deprived of water and
food, nesting places should be destroyed, all holes should be plugged
with concrete and cement and rubbish should be removed regularly. Rats
and mice can be caught by using man made traps and cages, and then be
killed. Use of natural predators like cats and dogs are fatal to the
rats but at the same time harmless to humans and pets. Most
effectively and widely methods used to control rats is the use of
rodenticides poisoned baits. Fumigation may be done in godowns and
rodents burrows. Different combinations of controlling methods may be
used suited to individual situation.