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multiplication. The high temperatures and humidity in the tropics result in
many generations per year, e.g., Plutella xylostella, the diamondback moth,
produces up to 28 generations per year in Malaysia (Ho 1965). In irrigated
areas, the asynchronous planting of rice has resulted in increased pest populations,
particularly of specialized pests, when compared to the previous
seasonal planting (Loevinsohn and Litsinger 1989).
Cropping systems in developing countries are often complex. Multiple cropping,
where two, three, or more crops are rotated in the same field during a
year, and intercropping, where two or more crops are grown in the same field
at the same time, are common. In addition, a one-farm family may be growing
different crops in different parcels of land at the same time. The agricultural
landscape is, as a consequence, much more complex and diverse in both time
and space than the monocultures typical of developed-country agriculture.
Land holdings are usually small (0.5 to 4 ha) and there are, therefore, a large
number of farms and farmers. Typically 50-75% of a developing country's
population is directly engaged in agriculture. In Thailand, for example, over
38 million people are directly involved in agricultural production.
Farmers often have little formal education, are illiterate, or in some countries
speak a language or dialect different from the national language. However,
they often have considerable traditional knowledge about agricultural practices
that is usually ignored by agricultural researchers and extension agents.
Developing-country farmers are often poor. They have no cash to purchase
inputs and often little access to formal credit. Informal credit may be available,
but interest rates are high. It is only for the major cash crops (vegetables, rice,
wheat, etc.) that government-supported credit schemes are available for the
purchase of inputs. Farmers also have little equipment. Sophisticated sprayers
cannot be purchased or maintained by small farmers. The backpack sprayer
is the usual method of application for chemical pesticides; however, these
sprayers are often ill-maintained and leak, causing a high degree of operator
exposure. Protective clothing is often not available or not used.
Research and extension efforts directed toward pest management are limited.
There is no international institute or board devoted to developing appropriate
pest-management techniques for developing countries and often methods and
technologies from developed countries are transferred with little in-country
testing. There is usually a high farmer-to-extension-agent ratio and extension
workers know little about pest management.
Priority support has been given by the (former) Agriculture, Food and Nutrition
Sciences Division of the International Development Research Centre
(IDRC) for research that benefits the small-scale farmers of the developing
countries. This has led to a concentration on the complete farming system and
researchers who work closely with farmers. IDRC support for research in pest
management has been in two areas: developing alternatives to chemical
pesticides where current use is high; and finding low-cost alternatives for
areas and subsistence crops that now use little, if any, pesticide.
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