The Effects of Pesticides on Agriculture

The growing demand for enhanced food productivity to meet the needs of the global population has led to use sophisticated agriculture technology in which pesticides play a crucial role. Pesticides are extensively used to increase agricultural products by preventing, controlling, or lessening the damage caused by a pest (John et al., 2001). Pesticides have been widely used througout the world since the middle of the last century. They are mainly used in agriculture and animal production, both including substances with high toxic effects and persistance in the environment (Beyer and Biziuk, 2008).

Pesticide residues in livestock generally accumulate by two ways. Either pesticides are applied to animals through insecticide-impregnated ear tag, spray, self treatment back rubber, dust bags, injectable or through pesticides spray on agricultural crops and fodder (Poppenga, 1999). Pesticide use has a positive and dramatic effect on agricultural production through protection of crops against insects, pests and diseases (Kaeew et al., 1996). Also for all pesticides to be effective against the pests, they must be biologically active, or toxic. Because pesticides are toxic, they are also potentially hazardous to humans, fauna, animals and environment in general (Vega et al., 2005). At the same time, the livestock reared on pesticides contaminated soils, crops, and fodders may accumulate considerable residues in edible tissues. For example the accumulation of dieldrin residues in sheep from ingestion of contaminated soils was studied and it was concluded that dieldrin concentration in the fats of sheep that consume dieldrin contaminated soil fall within 10 days of removal from the source of contamination. However, dieldrin accumulates in the wool of sheep that consume dieldrin contaminated soils (Paton and Petterson, 1997).

In Pakistan, pesticides are pre-dominantly used in the provinces of Punjab and Sindh. Some pesticides are biodegradable while others persist in the soils for longer times (Tariq et al., 2006). Pesticide residues have been detected in the vegetables in Karachi (Perveen et al., 2005), in fruits and vegetable in Islamabad (Tahir et al., 2001) and in various tissues of fish in the local lakes (Saqib et al., 2005). Futhermore, pesticide residues also accumulate on cropland soil (Jabbar et al., 1993). Animals can accumulate these substances from contaminated feed and water. Also, due to the lipophilic nature of these pesticides, milk and other fat-rich substances are the key items for their accumulation (John et al.