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  • Biopesticides provide a viable alternative to conventional pesticides

Nov 10, 2015-

The modern use of chemical pesticides dates back to 1867, when Paris green, an inorganic compound was first used to manage Colorado potato beetle. After that, various inorganic or plant-based pesticides came into existence. The successful discovery of the dichloro-diphenyl-trichloroethane (DDT) by a Swiss scientist Paul Hermann Müller in 1939 opened the floodgates of pesticide synthesis and use, especially for the control of agricultural pests and vector-borne diseases. 

In Nepal, DDT and pyrethrum, brought in exclusively from the US, were used in the 1950s to control malaria near the Gandaki Hydropower Project. Subsequently, in November 1952, DDT became the first chemical pesticide to be introduced in Nepal by the Ministry of Health. Then in 1955, Paris green, Gammexene and nicotine sulphates were also imported to eradicate malaria. These pesticides were mostly provided by the US Agency for International Development, which was sponsoring programmes primarily for the control of vector-borne diseases. Different groups of pesticides were introduced in Nepal in different periods. Organochlorins were introduced in the 1950s; organophosphates in 1960s; carbamates in 1970s; synthetic pyrethroids in 1980s. 

Though the use of such chemical pesticides provides instant benefits, they could have various negative impacts on human beings, and cause other environmental problems too. More often than not, pesticides break down the resistance of the pests against the toxicity of the pesticides leading to pest outbreak, resistance and resurgence. This led to the emergence of the notion of integrated pest management with a special focus on biopesticides—pesticides that are derived from animals, plants, bacteria, and certain minerals. 

Chemical effects 

Nepal needs to pursue organic agriculture as it promotes an environmentally, socially and economically sound production of crops keeping the natural capacity of plants and local conditions in mind. It aims to optimise quality production. And there can be no better time than now for Nepal to go organic. Many places in Nepal are still beyond the reach of chemical inputs due to lack of transportation facilities. This leaves us with plenty of time to make farmers in those areas aware of the side effects of using chemical pesticides. Inorganic farming techniques also results in the deterioration of soil quality.

However, considering the level of awareness among food producers and the scale of production, Nepal is still at its early stages in organic agriculture. On the one hand, organic inputs such as organic fertiliser and biopesticides are still not widely available while on the other hand, Nepali niche products are yet to be certified. 

Meanwhile, the commercialisation of agriculture in the country has led to a drastic increase in the use of chemicals in farming. Even though the average fertiliser and pesticides consumption in Nepal is very low (26 kg and 142 gm active ingredients per hectare respectively), injudicious use of chemicals is widespread especially in commercial farming. Panchkhal in Kavre is the best example of the severe consequences of mishandling and the overuse of chemical pesticides. Many people in Panchkal have reported skin irritation, headache, nausea, and in some cases, skin cancer. 

Therefore, there is a pertinent need to increase the availability of effective alternative pest control compounds in Nepal. To do so, we will need to battle the influence of multinational companies that promote chemical pesticides. Most farmers are tempted by the higher returns that numerous companies selling chemicals promise them. They feel that the higher price of organic products does not compensate for its lower yield. To address this issue, the Department of Agriculture through the involvement of Plant Protection Directorate has initiated Rapid Bioassay for Pesticide Residue facility in Kalimati vegetable market in Kathmandu. It has been revealed that some of the vegetables produced in some pocket areas contain pesticide residues beyond acceptable levels indicating the need to intervene by encouraging 


Hope for biopesticides

Against this backdrop, it would be best for Nepal to pursue organic farming. Moreover, organic cultivation is more suited for farmers with small land holding and the majority of Nepali farmers own less than a hectare of land. By taking up organic farming, farmers can secure a good income. And they could use biopesticides to fight pests. For example, there is an insect pathogenic fungus, Metarhizium anisopliae, which has been found to be effective on a range of insects. It could replace the need for synthetic pesticides. The bacteria based Bt, nuclear polyhedrosis virus and protozoan parasitoids are other bioagents whose formulations are available in different forms. Trichoderma is another useful biofungicides, effective to plant disease. 

Biopesticides are usually inherently less toxic than conventional pesticides. They generally affect only the target pest and closely related organisms in contrary to conventional pesticides that affect a wide range of birds, insects and mammals. Biopesticides are often effective even in small quantities and often decompose quickly, thereby resulting in lower exposures and largely avoid the pollution problems caused by conventional pesticides. Furthermore, as Nepal lies in between China and India it could sell its products to its giant neighbours as their massive population indicates a great demand for food. Nepal could use this to its advantage by shifting to organic production and create a niche for its products in the neighbouring markets. 

Yubak Dhoj G. C.

G.C. is Director General of 

Department of Agriculture 

Published: 10-11-2015 08:53

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