Crop protection is one of the major components in achieving
higher yields of the crops. The better quality of food, clothing, shelter and
some essential drugs, which are dependent directly or indirectly upon growing
plants, rather than, the maintenance of human life and animals is not possible.
Crop protection is concerned with the health and productivity of growing plants.
The disease losses are hazards, which can be minimized only by a continuous
process of research and education. To evaluate and solve new disease problems,
is the responsibility of the crop protection. To work out practicable
procedures, which growers can adapt to their needs and in a result, the farmers
must be benefited, is the aim of crop protection.
The plant disease can be defined as any disturbance or
deviation of a plant that interfere with its normal structure, function or
economic value. The diseases may be infectious or non infectious. In this case
living organisms, called pathogen, like fungus, usually cause bacterium,
nematode and insect pest, regarded as infectious diseases of all diseases. The
diseases may also be caused by other factors like physiological disorders. That
includes low or high temperature, unfavourable oxygen and soil moisture
relations, injurious atmospheric gases or chemical injury, lightening injury and
deficiencies or excesses of nutrients. The viruses are sometimes considered
living sometimes as non living, though are taken up independent existence of
their own. Therefore, plant diseases caused by viruses are sometimes regarded as
infectious, and sometimes as non-infectious.
Any injury or abnormality brought about by insects belongs in
the field of entomology. The remaining causes of all disturbance and deviations
are taken place in the field of plant pathology. The plant pathology constitutes
a big sector of plant protection, is a study of nature, causes and prevention of
plant diseases.
Plant diseases were present and well established on earth
long before human being established himself. The human being is facing with the
problem of protecting neighbouring crops from diseases since started settled
agriculture to till. The reason for man's problem is that both are competing for
the same resources needed for food, clothing, shelter and other requirements for
life survival. Plant diseases damage the crop, reduce the yield, lower the
quantity and quality, increase the cost of production and require cash outlays
for material and equipments for control measures. Besides, chemicals used for
disease control, are poisonous for human being and are main cause of
environmental pollution.
The importance of plant protection in relation to crop
production can be realized from the fact that in several crops the yields are
not of the desired level. Among the various factors responsible for low yields,
plant diseases are prominent and cause losses in world's crop production
amounting to many million rupees, which comes next only to losses caused by
insect pests.
The losses caused by the diseases are variable but their
cumulative effect is considerable, and in certain cases fields have been found
to show as much as 100 per cent damage. The record showed that there has been
severe attack of black stem rust of wheat and phyllody of sesame in 1906-1908 at
Mirpurkhas, whip smut of sugarcane in 1913-15 at Larkana, Wilt and storage rot
of potato and wilt of gram in 1914-15 at Karachi, early blight of potato and
long smut of sorghum in 1915-16 at Mirpurkhas, ring rot, tip burn and severe
attack of early blight of potato in 1918-21 at Karachi, Gram rot and grain smut
of sorghum in 1918-22 at Jacobabad, red rot of sugarcane and wilt or root rot of
cotton in 1921-22 at Sukkur, root rot and boll rot of cotton in 1922-24 at
Sakrand, blight of rice and grain smut of sorghum in 1927-30 at Larkana and Dadu
are some examples from previous record. While, during last two decades, some of
the above shown diseases as well as wilt and viral diseases of chilies and
tomatoes, mildew of cucurbits, mango, and jujube, banana bunchy top virus (BBTV)
and cotton leaf curl virus (CLCV) also take a heavy toll and the losses in
production.
The cotton crop record revealed that root and boll rot
diseases of cotton were considered as most severe and destructive in past.
Cotton leaf curl virus found to be most important disease since last decade.
This disease was first time recorded in 1967 at Multan on cotton plants. In
Sindh, this disease was first reported during 1996 at Ubauro, District Ghotki.
Now it is reached up to New Saedabad, District Hyderabad during last year
(1999-2000). It was considered a minor disease until 1987, but in 1991-92, it
infested 35,000 acres and 294,000 acres during 1992-93 causing a huge production
and monetary loss to the nation.
However, it is quite difficult to present accurate estimates
of the losses due to diseases, because it varies from year to year and from one
region to the other. The aim to elaborate all above actual and potential
hazards, damages and losses was determine crop diseases and it is becoming
obvious that: now, it is upon the crop protectionists including plant
pathologists and entomologists as well, to design and formulate ways or means to
combat all enemies of the crops, so that the losses caused to the crops may be
minimized. By now, it is very easy to decide that what is role of crop
protection in agriculture? What should be our priorities for identifying the
crop enemies, treating the suffering plants, and understanding the nature of
diseased plant?
However, Table 1 present yield per hectare of some of the
most important (major) crops of Pakistan. The causes of fluctuations in
production may be many more, but diseases and insect pests as well as weeds may
also could not be ignored, neglected and or regretted, because they also cause
variable loss time by time to the crops. A major quantity of pesticides are used
for the control of major pests of cotton, viz. white fly, jassid, thrips, mite,
American boll worm, pink boll worm and spotted boll worm. White fly becomes top
most important cotton pest, because the disease cotton leaf curl virus (CLCV)
transmitted by it. Other field crops as well as vegetable and fruit crops are
also not free of insect pests or diseases. Most of the growers are of the
opinion that these all enemies could only be controlled by use of pesticides.
The wheat and some other crops were felled free of pesticides, but nowadays they
are also in target due to common use of weedicides. Therefore, I think no any
crop is free of (safe to) pesticides. Table 2 indicates off take and imports of
pesticides. Pesticide is a combination of two words: 'pest' and wide'. Pest
means the agent that cause any disturbance, deviation or abnormality in normal
function and structure of the crop and cause loss. The word, wide' means poison,
which is used for killing or controlling the cause of disease or any enemy,
which cause damage to the crops. Insecticides are used against insect pests. The
fungicides against fungi and nematicides against nematodes, while antibiotics
are used to control bacteria. The herbicides or weedicides are applied against
herbs or weeds, because they may compete with crops for nutrition as well as for
other requirements and sometimes becomes a harbour for flies and other insects.
These all (Insecticides, fungicides, nematicides, antibiotics and herbicides or
weedicides) are pesticides.
|
Table 1:
Yield (Kg per hectare) of some of the most important
(major) crops of Pakistan.
|
|
Year |
Wheat |
Rice |
Sugarcane |
Maize |
Gram |
Cotton |
|
1990-91 |
1.841 |
1.543 |
40.770 |
1.401 |
485 |
615 |
|
1991-92 |
1.990 |
1.546 |
43.371 |
1.419 |
514 |
769 |
|
1992-93 |
1.946 |
1.579 |
43.024 |
1.364 |
344 |
543 |
|
1993-94 |
1.893 |
1.826 |
46.144 |
1.380 |
393 |
488 |
|
1994-95 |
2.081 |
1.622 |
46.747 |
1.481 |
524 |
557 |
|
1995-96 |
2.018 |
1.835 |
46.968 |
1.602 |
607 |
601 |
|
1996-97 |
2.053 . |
l.912 |
43.521 |
1.607 |
540 |
506 |
|
1997-98 |
2.238 |
1.870 |
50.288 |
1.627 |
696 |
528 |
|
1998-99 |
2.170 |
1.928 |
47.784 |
1.730 |
648 |
512 |
|
1999-2000 P* |
2.247 |
2.050 |
45.904 |
1.512 |
612 |
641 |
| P:
Provisional, *: Jul.-Mar, Source: Economic Survey, 1999-2000, Govt. of
Pakistan. |
|
Table 2: Off take and imports of pesticides. |
|
Year |
Import of pesticides
Quantity' (Tonnes)
|
Value(Min. Rs.)
|
|
1990-91 |
13,030.1 |
1,489.43 |
|
1991-92 |
15,258.3 |
1,945.98 |
|
1992-93 |
14,434.8 |
1,730.60 |
|
1993-94 |
12,100.4 |
1,706.30 |
|
1994-95 |
21,776.1 |
2,978.10 |
|
1995-96 |
3,047.9 |
5,080.70 |
|
1996-97 |
30,855.9 |
5,272.49 |
|
1997-98 |
18,195.2 |
3,010.10 |
|
1998-99 |
17,913.0 |
3,101.18 |
|
1999-2000 P* |
19,148.0 |
3,740.00 |
| P:
Provisional, *: Jul.-Mar, Source: Economic Survey, 1999-2000, Govt. of
Pakistan. |
Actually, the pesticides are equally poisonous to all
livings. It means the pesticides do not kill only the insect pests, disease
causing or inciting organisms and weeds, but also may hit the useful insects,
birds, all animals and even human beings directly or indirectly. Therefore, only
proper use of pesticides is recommended by adopting IPM, IPDM or IWM.
IPM stood for integrated pest management, IPDM for integrated
plant disease management and IWM for integrated weed management. The word
integrated means combination, implemented as bringing together of individual
control measures into a collective operation. The pest, disease or weed
management means to check, prevent or control insect pests, diseases or weeds by
a judicious use of various methods of control, with the intention of reducing
the incidence (damage or harm), caused by insect pests, diseases and weeds to an
economically acceptable level. In other words, integrated pest, plant disease or
weed management is a programme, in which nature; the farmer (grower) and
pesticides (insecticides, fungicides, weeds or so) together combine to control
insect pests, plant diseases and weeds. It means application of all those
resources and practices, which may help, initially for prevention and finally to
control insect pests, plant diseases and weeds, is called integrated pest, plant
disease or weed management.
There are so many methods, which are applicable, either
adopting singly or in combination one with another, but the use of several
techniques in combination, usually is more successful and most efficient, than
any one method used alone. Integrated pest, disease or weed management can lead
to less expensive agricultural production technology, a substantial reduction in
pesticides uses, a greater stability in vegetation system, and an improved
environment. It is because that integrated pest, plant disease or weed
management is a mix of biological, cultural and chemical practices with the
involvement of all preventive and chemical practices, with the involvement of
all preventive and curative control measures against insect pests, diseases and
weeds.
However, there is really very much more importance of crop
protection in the economy of country, in view of both, negative and positive
effects on over all crop production (yield), as well as trade and corporation of
pesticides, with special reference to import and marketing (distribution) for
control of insect pests, diseases and weeds. Now, it is up to researchers that
on what aspects of crop protection they would like to conduct research studies.
How the extension workers gain knowledge of recent research achievements in the
field of crop protection and transfer the same amongst the growers. Likewise,
what the growers (farmers) would like to decide for adopting modern crop
protection technology (IPM, IPDM and IWM), so that they could save or protect
their crops from different enemies (insect pests, plant diseases and weeds) and
improve the economy of country.
The writer is Assistant Professor (Plant Pathology) Sindh
Agriculture University, Tandojam.
