Impact of - IDL-BNC @ IDRC - International Development Research ...

Because pesticides are required in small quantities, they are often repackaged
in pop bottles and paper bags with no labels. They are routinely stored near
food and the containers are often reused for food. Even when labels are
applied, they are often not in the local language or are of little use to farmers
who cannot read. Some Philippine vegetable producers have a 50% risk of
poisoning after 5 years of pesticide use (Rola 1988). In Central Luzon, Philippines,
a 27% increase in deaths among the most at-risk population occurred
after the introduction of pesticides (Loevinsohn 1987).
Many pesticides considered safe under developed-country conditions are
unsafe under conditions found in tropical developing countries (Loevinsohn
1989). No matter how many improvements are made in applicator safety and
farmer education, certain chemicals are still too dangerous to use in this
environment. This relates primarily to classes of chemicals (organophosphates)
that are considered to be more toxic to humans than recently developed
insecticides. However, pyrethroids, which are considered to have low
human toxicity, can also have considerable effect on people applying them
under tropical conditions (He et al. 1989).
There is little information on the wider environmental effects of pesticides on
nontarget organisms in developing countries. In Southeast Asia, there is
anecdotal evidence for loss of diversity, particularly among beneficial insects,
and in rice-growing areas considerable reduction in numbers of frogs and fish
in paddy and irrigation waters where pesticides are used.
As many as 1 400 insect pests may be resistant to synthetic insecticides. The
diamondback moth (Plutella xylostella L.) in Southeast Asia is resistant to all
classes of synthetic insecticides and also shows cross resistance to a number
of others (Cheng 1986; Rushtapakornchai and Vattanatangum 1986). In addition,
it may be resistant to the new class of insect growth regulators and Bacillus
thuringiensis. Resistance to insecticides is compounded by the farmers' practice
of often mixing a cocktail of insecticides and using application rates much
higher than recommended.
It is clear that synthetic chemical insecticides as currently used are not the
solution to pest management in developing countries. However, answers to
the problem of pest control are desperately needed.
Breeding
Alternative solutions
Plant breeding for resistance to insects and disease has been very successful.
The international agricultural research centres (IARCs) have had notable
successes in major crops (rice, wheat, and maize). However, this has led to the
planting of large areas with few varieties (e.g., Indonesia grows only three
varieties on 90% of its rice area). In these situations, when pesticide resistance
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