An end to pesticide use?
Date: Wed 27-Oct-1993
Paper Page: 29A
Publication: Daily Nation
WASHINGTON -- Farmers in the Caribbean and other parts of the developing world
may get significant help in fighting plant pests in years to come by using
natural enemies of the pests rather than chemicals that harm people and the
environment.
Scientists conducting research in the Philippines, Nigeria, Taiwan, Colombia and
India have reported new biological techniques that will allow farmers in
developing countries to dramatically reduce their use of chemical pesticides
while increasing agricultural production.
Farmers often overuse pesticides, harming themselves economically, said the
panel of researchers. Farmers also often do not wear equipment that will protect
them from the dangerous ingredients in the pesticides they are spreading.
As a consequence, in the Philippines, for example, rice farmers have five times
the number of eye problems and twice as many respiratory ailments as
non-farmers, said Kenneth Fisher, deputy director general for research at the
Manila-based International Rice Research Institute.
"In many cases, when one takes health costs into effect, it negates the
benefits of pesticides," he said at the panel brought together by the
Consultative Group on International Agricultural Research (CGIAR), an umbrella
for 18 international agricultural and forestry research centres.
Traditionally, the centres concentrated on developing high-yield varieties of
crops that might or might not need heavier dosages of pesticides to increase
production.
Twenty years ago, Asia faced mass starvation and it was the high-yielding
varieties of wheat and rice developed by the centres that alleviated that
crisis, Per Pinstrup-Andersen, director general of the International Food Policy
Research Institute in Washington, said as moderator of the panel.
But environmentalists around the world began arguing years ago that the
pesticides not only polluted the land and waters and harmed the health of
farmers, but also were not as effective as natural enemies of harmful insects
and weeds.
Comments by the panellists suggested that the centres now advocate a system
called "integrated pest management" which uses a variety of
biological, physical and chemical methods working together to control or
eradicate the insects and weeds that attack crops.
Fischer said his study in the Philippines indicates that chemical pesticides are
not needed to control rice pests but are needed to prevent the spread of weeds.
Hans Herren, director of the plant health management division of the
International Institute of Tropical Agriculture in Nigeria, said locusts are now
swarming over fields across the African Sahel, the southern part of the Middle
East, Pakistan and India.
Insecticides so environmentally destructive that they have been banned in many
countries have been used routinely in places where infestations break out, he
said.
"We have been down the pesticide road but the problem still remains,"
he asserted.
Research at his centre indicates, however, that a natural fungus, metarhizium
flavoviride, can be mixed with small amounts of oil and sprayed where
locusts land and breed.
The fungus harms no plants or other animals, including humans, he said.
A tiny wasp is being used to destroy the diamondbacked moth, the most
destructive pest of five important vegetable crops, said N.S. Talekar, an
entomologist at the Asian Vegetable Research and Development Centre in Taiwan.
The moth is developing immunity to pesticides used on cabbages, broccoli,
cauliflower, radishes and Brussels sprouts. Tests indicate that using the wasps,
which feed on the moth, can reduce pesticide use up to 80 per cent.
A pilot programme on 7 000 hectares in the Philippines indicates that farmers
are saving about US$10.5 million a year by spreading the wasps in their fields
rather than pesticides, he asserted.
A mix of six to 12 predatory mites has been tested successfully against the
green spider mite, the major pest attacking cassava in South America and Africa,
Anthony Bellotti, a senior entomologist at the International Centre for Tropical
Agriculture in Colombia, said.
Small companies in Colombia and Brazil have begun breeding and distributing the
killer mites to farmers in their areas, he said.
Tests are being conducted to determine whether a wasp that could be bred by
farmers would destroy large enough numbers of the hornworm that attack cassava
to be useful.
Donald Blyth, director of the cereals programme of the International Crops
Research Institute for the Semi-Arid Tropics in India, said a disease-resistant
variety of pearl millet has finally been found.
Biotechnology research over the next five years should be able to overcome
completely the disease known as downy mildew, he said.
"In 1993, we have the enemy under control and believe we are poised for the
knockout blow." (CANA)