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Integrated Pest Management for optimum output
By M. Mithal Jiskani
DISEASES limit the production of vegetable and fruit crops.
Some are easy to identify but others difficult. Effective
disease management is essential for high quality production.
Its control includes crop rotation; planting resistant and
certified disease-free seeds or seedlings; timely sowing or
planting in well-prepared, fertile soil; controlling weeds and
insect pests; following a fungicide spray programme and
practising clean plough down after harvest.
 Incorrect
identification of disease may lead to wrong management
practices, wastage of time and expenses resulting in crop
failure. Insecticides do not control diseases caused by
bacteria, and viruses are not controlled with most fungicides.
Similarly, a particular fungicide may control only one fungal
disease but not another. The growers should learn to recognize
more common diseases by their symptoms and should have
sufficient knowledge to select appropriate management
practices for in a particular situation.
Wind, water or rain, and equipment can spread the disease
causing organisms (pathogen) viz. fungus, bacterium, nematode
or virus, once introduced in a field. The grower or field
worker, the insect pests, birds, and animals help the
disease-causing organism to spread.
Even the higher pathogens may become carrier for another
disease. For example, viruses are transmitted through fungi
and nematodes. The dry and wet, as well as hot and cool
climates increase the development and spread of the disease.
The disease inciting agents perpetuates (survive from season
to season) through the seed given from diseased crop, weed
plants, infested fields and all plant debris.
The Integrated Pest Management (IPM) involves the use of
several different strategies and the judicious use of
pesticides for management of diseases and other pests of the
crops. The most beneficial and economical control of diseases
and insect pests may be achieved through the IPM as compared
to any single management practice, such as the pesticide
application.
The weed and insect management are also important components
of disease control in an IPM system, because infection and
spread of some pathogens is associated with the presence of
certain weeds (alternate hosts) and insects (vectors).
However, the disease management strategies, effective
components of an IPM system, are given below with the hope
that the growers will adopt these for the benefit of all
because chemicals applied for the control of diseases and
insect pests are equally poisonous for all living things and
is a major source of environmental pollution. Their
effectiveness in controlling specific diseases could be learnt
through regular study and observation.
Crop rotation: The fungi, bacteria, and nematodes cause soil
and seed borne as well as foliar diseases. These pathogens may
survive from season to season in the soil or on seeds and
other crop debris in soil and build up to damaging levels with
repeated cropping therefore 3-4 year rotation with non-host
crops is recommended.
Site selection: Most crops are best grown on sandy loam, sand,
or silt loam soils with a pH of 6 to 7. Growth on acid and/or
poorly drained soils often results in increased incidence of
Fusarium wilt, fruit rots and some other diseases. Therefore,
maintaining records of the disease history of fields is
beneficial for avoiding disease problems or implementing
preventive measures. In such a situation, late plantings are
not situated near early plantings where a disease already
exists.
Sanitation: Several destructive diseases of various crops can
be spread from infested fields to clean fields in soil and
crop debris carried on equipment and workers. Therefore, the
equipments and boots should be washed to remove all clinging
soil and debris when leaving the infested fields. Clean fields
can also be worked before entering the infested fields.
Variety selection: Resistance is the most effective and
economical means of disease control. Therefore, available
disease resistant varieties should be planted where possible.
Soil fumigation: Soil fumigation is expensive and potentially
dangerous for inexperienced applicators, but increases yields,
earliness, and controls soil borne diseases. However, row
fumigation may be economically feasible mostly for vegetables.
Planting time: The planting time may favour or may not the
multiplication of disease inciting organisms. Therefore,
change in planting time is recommended in various cases. For
example, cultivation of early sowing and early maturing
varieties are recommended for the control of rust in wheat.
Disease-free seed and seedlings: Some diseases may be seed
borne or introduced in fields on infected seedlings
(transplants). Efforts should be made to obtain disease-free
seed and transplants. Seed dressing fungicides are found
effective in minimizing the potential for seed borne diseases
caused by fungi and to help assure establishment of an
adequate stand. Only healthy or treated seed and seedlings
should be used to initiate plantings.
Weed control: Mostly the weeds serve as alternate hosts or
sources of infection for virus diseases. Therefore, effective
weed control practices should be utilized in and around the
crops.
Insect control: The insects are major source to transmit virus
and bacterial diseases. Therefore, insects must be controlled
when warranted in and around the crops.
Irrigation: Excessive irrigation or frequent irrigation with
small amounts of water as well as shortage of irrigation
(drought conditions, due to long irrigation intervals) favours
spread and development of many diseases. Therefore, the crops
should be irrigated properly.
Fertilizers: Heavy doses of nitrogenous fertilizers may
maximize but judicious use of potassic fertilizer helps in
minimizing the susceptibility of plants. Therefore, proper use
of fertilizers is recommended.
Chemical control: Fungicides protect healthy plants from
infection, but do not cure diseased plants. These are needed
for effective management of some foliar diseases caused by
fungi. Copper sprays are also useful in reducing foliar
diseases caused by bacteria.
The diseases are more difficult to control once established;
hence timing of the first spray is critical. The first spray
should be made before symptoms appear where diseases are
anticipated or shortly after symptom appearance. Moreover, an
adequate spray volume is needed to achieve thorough coverage
of infected plant or tree. Thereafter, an approved schedule
should be maintained.
Sprays should also be applied before an anticipated rain event
rather than after because this affords protection during
periods favourable for infection. Most soil borne diseases
cannot be controlled by foliar fungicide application, but
drenching may be found useful in such condition.
Scouting: Scouting allows for early detection of all pests and
diseases so that timely management practices can be
implemented. Plantings should be scouted regularly (at least
once per week), for assessment of the effectiveness of
management programs already implemented.
Residue management: Many of the pathogens survives in and on
the plant debris or pruned parts of plants or trees, therefore
theses should be incorporated into the soil by ploughing or
disking after harvest to hasten decomposition.
Courtesy: The Dawn
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