Sumayya Khalid

Pest attack on different crops has been recognized as one of the major constraints to exploit the quality, yield and genetic potential of crops. These problems lead to loss of about 1/3 of the world’s agricultural production every year. The major pests that affect crops are white backed plant hopper, stem borer, fruit flies, leaf folder, mealy bugs, and beetles etc.  Pesticides are substances that control a variety of pests and weeds invading the agricultural crops. Pesticide includes insecticides, herbicides (weed killer), acaricides (mites and ticks killer), nematicide (used to kill parasitic nematodes), molluscicide (used to kill slugs and snails) and fungicide etc.

Pesticides belong to four chemical groups which are organochlorines, carbonates, organo-phosphorus and pyrethroids. Organo-chlorines belong to chlorinated compounds having high persistence in the environment. DDT, dieldrin, and hexachlorocyclohexane (HCH) are most widely used organo-chlorines in developing countries due to low cost and need against various pests. Pesticide utilization in Pakistan started in 1954 and is currently on the rise. 88.3% of pesticides are being applied in Punjab, 8.2% in Sindh and 2.8% in KPK and Balochistan. Pesticide use in Pakistan is focused on cash crop cotton (61.92%) followed by on fruits and vegetables (11.9%), rice (11.86%), sugarcane (6.14%), maize (4.83%) and oilseeds (2.21%). Out of the total pesticides in Pakistan, insecticides comprise 90% followed by herbicide 7%, fungicides 3% and others (acaricides, fumigants) 0.2%.

Even after many years of spraying pesticides water, air, and soil contamination have been increased due to bioaccumulation, long half-life, and long-range transport of pesticides. It has threatened both the human and environmental health. Annually above 500,000 Pakistanis suffered from agro-chemicals poisoning, out of which 10,000 died. Although the use of pesticides in Pakistan is not higher than other Asian countries but misuse of pesticides is common which is threatening human health and causing environmental problems. Farmers have poor knowledge about the pesticide. They consider pesticides as a medicine rather than a source of poison. They apply pesticides on calendar basis without knowing about crop condition, natural enemies, and a population of pests.

Farmers also lack knowhow about pesticides application. Most of the pesticide applied hits the non-target areas. In this way, pests develop resistance against pesticides and farmers have to repeat pesticides application without getting the desired results. Mostly, due to lack of knowledge and resource limitations, farmers use improper insecticides (e.g. use leftover insecticide on vegetables which is actually for cotton). These pesticides contaminate the vegetables and persist longer. Majority of the farmers do not monitor their fields and apply the pesticides when symptoms have become quite visible and almost damage has been done. At this condition pesticides application leads only towards environmental pollution. Pesticides leakage is also a serious issue which occurs during pesticide application, store, and transport. Only 19% of the farmers get training about protective spraying and handling of pesticides. Protective measures include the use of masks, avoid eating or drinking during pesticides spray and washing hands and face after finishing the spray. Farmers do not bury the empty containers in soil and throw them in water canals or in the courtyard which contaminates the environment and affects the humans and animals. Even in most cases, these containers are used to store edible oil, milk, and water.

Integrated Pest Management

Most of the farmers have no knowledge about integrated pest management. They ask which insecticide is best instead of asking how to control a particular pest. They consider only one solution which is the use of pesticides.

IPM is a common sense technique which is a cluster of cultural, mechanical, biological, genetic, and chemical techniques. It is based on breed, and intensity of a particular pest. The emphasis of IPM is on control of the pest, not eradication. It first works to establish acceptable pest levels which are called action threshold and to apply controls if thresholds are crossed.

  • Preventive cultural practices: It involves selection of best varieties of crops to maintain healthy crops.
  • Monitoring: Regular crop observation is critically important. Visual inspection and insect traps are used to monitor levels of the pest. Record keeping is also important which provides knowledge about behavior and reproductive cycle of the target pest.
  • Mechanical controls: This method is used when pest population is increased at an unacceptable level. It may include simply hand picking, traps, and barriers to disrupt breeding.
  • Biological controls: It provides control at low cost with minimum environmental impact. This approach involves the use of beneficial insects that feed on target pests. Biological insecticides, derived from microorganisms (entomopathogenic nematodes and Bt, entomopathogenic fungi) also fall in this category.
  • Responsible use: Synthetic pesticides are used as required in the life cycle of the pest. Pesticides application must reach their intended targets. Cost of labor and pesticide use can be lowered by using low volume spray equipment.

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