Ibadan, Nigeria
August 22, 2008
A joint biological control study
conducted by
International Institute of
Tropical Agriculture (IITA) and the
University of Ghent -
Belgium has found that certain species of nematodes could be
used against crop pests in Sub-Saharan Africa (SSA). The study,
carried out in the humid forest zone of South Cameroon,
identified and isolated native species of entomopathogenic
nematodes (EPNs) that could be effectively deployed as
biological control agents against a wide range of insect pests
of crops in the region.
EPNs are microscopic roundworms similar in morphology to plant
parasitic nematodes but differ in their target hosts. They are
termed ‘entomopathogenic’ as the nematodes kill the insect host
from within. EPNs also rapidly kill their pest hosts, usually
within 48 hours. They reproduce until the resources in the
cadaver are depleted, then they migrate in search of new hosts.
The project included isolation of local EPN species,
characterization of isolates and associated bacteria, matching
of EPN species with the insect pests, development of suitable
application strategies, determination of nematode/bacterium
associations for commercial production, mass production of EPNs
for distribution to farmers, and conduct of training on the
effective use of EPNs.
According to Ir. Françoise Kanga Messiga, coordinator of the
project, “EPNs are more effective when they are incorporated as
a component of an on-farm integrated pest management (IPM)
system. Within limits, EPNs are compatible with the use of
chemical pesticides since their virulence is not affected. More
importantly, using EPNs is safe for users and the environment as
their associated bacteria poses no threat to vertebrates or
plants”. However, she cautions that EPNs may affect some
beneficial insects such as pollinators.
She adds that in SSA, many families of insect pests could be
potentially targeted by EPNs. These could include pests of major
crops such as banana, cowpea, coffee, cotton, cocoa, cassava,
cocoyam, yam, taro, groundnut, maize, oil palm and certain
fruits and vegetables.
For years, pesticides have been the mainstay of crop protection
against insect pests. Many large farms and companies in SSA
producing cash crops such as banana, cocoa, coffee, cotton, oil
palm, plantain and tomato routinely and intensively use chemical
pesticides. For example, from 1992 to 2000, Ethiopia imported an
average of 1452 tons of pesticides annually. In Ghana, about a
million liters of Lindane (a neurotoxic insecticide) were
estimated to be in store in 2001.
Unfortunately, not only are pesticides harmful to the
environment but pests also develop strong resistance against
them. Millions of farmers have also been exposed to hazardous
chemicals because of inadequate awareness or training on their
correct choice and use. Their use is also costly for small-scale
farmers – as much as US$ 97 per ha in West Africa. As such,
classical biological control using natural enemies of pests
presents a better alternative especially if deployed as part of
an IPM strategy.
Worldwide, EPNs have been successfully used to control insect
pests, especially in tropical regions. In Brazil, Venezuela and
in the tropical areas of Australia, they have been applied to
manage banana weevil. In Colombia, native EPNs are used against
the coffee berry borer. In Egypt, larvae of the diamond back
moth succumb to the bacteria of at least two EPN species. The
cotton bollworm, which also attacks chickpea and tomato, has
been shown to be susceptible to EPNs. Most of the EPNs used are
native to the countries mentioned. To obtain high efficiency,
EPNs must be adapted to local environmental conditions.
However, information on indigenous EPNs in Africa is still
limited, especially in SSA. Currently, documented studies are
available only from Kenya and Ethiopia. The IITA – University of
Ghent project addressed this by prospecting for populations of
EPNs indigenous to SSA and suitable for biocontrol of pests in
the region.
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