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[Duurzaamlijst] Afleidingsplanten (en meer)


In het Engels maar een mooi voorbeeld van afleidingsplanten (en 

For details of how to obtain a video about ICIPE's work see:
(Florianne Koechlin, June 2000)

Articles, information on ICIPE and biological pest-control:
www.icipe.org and www.blauen-institut.ch

Together with a group of journalists I spent a week at the
Research-Institute ICIPE (International Centre of Insect Physiology
and Ecology) in Kenya. I came home all enthusiastic about their
projects, about their innovative approaches to tackle some of 
key-problems in agriculture. The ICIPE specialised on biological
pest-control. Modern science is used to search for cheap and
sustainable solutions to control stemborers, tsetse-flies,
locust-swarms, ticks, fruitflies, anopheles-flies (vectors of malaria)
etc. The collaboration with and capacity-building of farmers is

Stemborers and the push-pull system

We're in West Kenya, in a field station of ICIPE near Lake Victoria.
The small maize-field in front of us looks dreadful: the plants are
only 1 m high, the leaves yellow and full of holes, and there are
almost no cobs at all. Close by, Mrs Ouzo, the farmer of these 
shows us another maize-field -- the plants are over 2 m high, with
darkgreen leaves and healthy cobs. It's the same maize-variety on 
fields, planted on exactly the same day. The difference could not be

The first maize-field was destroyed by stemborers and striga
(witchweed), the two most important pests of maize and sorghum 
in all
Africa. Stemborers can destroy up to 80% of the crop in no time, 
loss of crops due to striga varies from 20 to 80%. If both pests are
present at the same time, they can easily destroy the whole crop.

Around the second field, Mrs Ouzo planted 3 rows of napier-grass. 
beauty of this grass is that its odours are attractive to stemborers",
says scientist Zeyaur R. Khan. "The grass then produces a gummy
substance that traps the pests. Only about 10% of the stemborer-
survive In the end". Between the maize-rows, Mrs Ouzo planted the
leguminose desmodium, an earth-covering plant whose odour 

The stemborer is attracted to napier-grass (Pennisetum purpureum) 
the outside of the field and repelled by desmodium (Desmodium
uncinatum) from the inside of the field -- this "push-pull"-system 
originally developped by ICIPE. Starting point was the knowledge 
stemborers must have been indigenous to East Africa long before 
was introduced there (about 100 years ago).

Originally, its host must have been different kinds of wild grass,
only later on, it specialised on maize, which had no resistance
against it -- but was all the more nutritious. For 4 years, Khan and
his team selected several species of wild grass with strong
stemborer-attracting odours and cultivated them in a garden near the
local station. Farmers from the surroundings were invited to choose
from the different varieties: they mostly preferred Napier- and
Sudan-grass, which both look very similar to maize and are good
fodder. Varieties of wild grass looking more like "weed" were left

The selection of "repellent-plants" was successful, too:
molasses-grass (Melinis minutiflora) reduced the loss of crop from 40%
to 4,6%. The analysis showed a complexe mixture of terpinoles,
nonatrienes and some more volatile molecules (nature, 14.8.97, p.
631). Also, the leguminose silver-leaf-desmodium is a good
stemborer-repellent. Furthermore, it binds nitrogen and thus enriches
the soil. It keeps the soil moist and protects it from erosion. But
most of all: desmodium is most effective against Striga -- to
everybody's surprise. With desmodium, striga is suppressed by a factor
of 40 compared to maize monocrop. Although striga is a very beautiful
weed with its pink blossoms, it is a most deadly plant. Striga is a
parasite to maize-roots. One single plant produces 20'000 tiny seeds,
that disperse easily. In all Africa, problems caused by Striga are
increasing. An ICIPE research project (funded by the Rockefeller
Foundation) examines the reasons why desmodium suppresses striga.

"Last year, I sold my napiergrass and desmodium as fodder for 6000
shillings (about 100$, FK). With this money, I could afford to pay the
school fees for my kids. This year, I am planning to produce
Desmodium-seed as well because all of my neighbours want to go for
this push-pull-system. Maybe, I can afford a cow then", says Mrs Ouzo.
As one of the first farmers, she was chosen for the project because
her fields were most heavily infested by stemborers and striga. ICIPE
plans to establish the push-pull-system not only in further areas in
Kenya, but also in Aethiopia, Uganda and Tansania, in close
co-operation with the national programmes.

Stemborers and a small wasp

Stemborers have natural enemies, which can be used successfully as

5 different species of stemborers exist in Africa, the most aggressive
one is the spotted stemborer (Chilo partellus). It was introduced from
India/Pakistan to Africa some 70 years ago. ICIPE scientists went to
India to do research in these centers of origin. They found Chilo
partellus being a harmless pest kept well under control by several
natural enemies. One of them is the little wasp Cotesia Flavipes
Cameron: it tracks down the stemborer larvae deep inside the stem and
lays its eggs into the pest; these then hatch out and consume the
borer from within. After careful testing, this wasp was released on 3
sites in Kenya.

By now, the wasps are well established; they not only go for Chilo
partellus, but for 3 other stemborer-varieties, as well. The latest
results show that stemborer-infestation could be reduced by 53% in
these areas. "Maize only came to East Africa some 100 years ago, and
had no resistance against the stemborer. The immigrated stemborer
Chilo partellus had no enemies. Any ecological balance that existed
between native stemborer and wild grasses was severly disturbed. We
try to reintroduce a natural equilibrium into this system", says Bill

I wanted to know if Cotesia flavipes could not harm other insects as
well. Overholt denied [this]: "The host range of this wasp is limited
by its searching behaviour, which restricts hosts to stemborer larvae
found tunneling inside the stems of larger grasses. And then only
certain stemborers, and only the later larvae instars of these, are
suitable for the development of the wasp-parasites. We made careful
evaluations, and we did not find one other insect matching all these

ICIPE is working closely together with national programmes in Kenya,
as well as in Uganda, Somalia, Mozambique, Malawi, Ethiopia, Zambia,
Zimbabwe and Zanzibar to release the wasp Cotesia in all of these

Stemborers and transgenic Bt-maize from Novartis

A third - and very different - strategy to fight the stemborer
consists in introducing genetically engineered Bt-maize. The African
stemborer-species are close relatives to the European corn-borer,
against which the Bt-maize was constructed. The Swiss company Novartis
wants to test and introduceBt-maize in Kenya: in spring 2000, they
started a 5-year program with Bt-maize, at costs of 6,2 million$, in
co-operation with the Kenyan Research Institute KARE and the
Latin-American CYMMIT.

This project was presented at a meeting in March in Nairobi, "which
turned into one single tribunal against Hans Herren (the director of
the ICIPE). They accused him of being an ennemy of Africa, and of
assuming Africans were incapable of handling biotechnology" (The
Tages-Anzeiger, 21.6.00). Klaus Leisinger, director of the Novartis
foundation for sustainable Development, accused Herren of having gone
to the Swiss development Agency to get them off GMOs. This is not
true. Hans Herren is critical, but he is not a strict ennemy of
genetic engineering, and he told an audience of Swiss governement
officials about his sceptisism:"Possibly, transgenic maize will be
part of the solution in the far future. But what about the other
problems? The interesting thing about the push-pull-system is:  It
already exists and the farmers use it. It was developped together with
the farmers. With the push-pull-method, we have an integrated solution
for the problems of the stemborer and striga. We have protein-rich
fodder, Nitrogen fertilizer and a good protection against
soil-erosion. All this within one field. It's a system that's
enhancing justice and a sustainable agriculture."

ICIPE - Integrated research on tropical insects

350 people work at the ICIPE, mostly Africans. The main issue of ICIPE
are Africa's most damaging pests, at costs of millions of lives
(humans and animals) each year and 30% crop-losses on average: the
Anopheles-mosquito (vector for malaria), the tsetse-fly (vector for
human sleeping sickness and several fatal animal-diseases, such as
nagana in cattle and sura in camels), the tick, the locust, the
fruit-fly (eg destroying each year 20-80% of the mango-crop) - and the
stemborer. Useful insects are studied as well: ICIPE initiated a local
silk-production with African silkworms and local honey-production.
Another main issue at the ICIPE is capacity building (from farmers to

Interdisciplinary teams of scientists are doing pioneering work in the
area of biological pest-control. They are working on insect behaviour
and population ecology, they study the ways of communication of
insects, they analyze the odours of insects and plants, and search for
the molecular conditions of vector-mechanisms, they do molecular
insect-taxonomie and search for ways to protect - and use - the vast
biodiversity. All the time, the goal is to use modern science to
develop simple and efficient methods that farmers can afford. "We are
looking for solutions in nature, we want to understand the system and
identify the weak links, where we can intervene. How can we favour
natural enemies of the pests, what odours will attract or repell them,
how can we reintroduce a better equilibrium?", says director Hans
Herren. François Omlin, a scientist who started to work at the ICIPE
recently, confirms: "I do not know of any other research-institute
worldwide, working in this area in a comparable interdisciplinary way
- in this place, molecularbiologists are working together with
behavioural scientists and entomologists. And furthermore, all of us
are in close contact with the farmers."

"Biological pest-control is not as sexy…"

Hans Herren, director of the ICIPE, won the World food prize in 1995
because he and his team could get control over the cassava mealy bug,
that was endangering the staplecrop cassava in large areas of Africa
(from Senegal to Moçambique) and threatening some 300 million people.
They got control over the bug with the help of a small wasp ? without
chemistry, and without any extra costs for the farmers. Thoughtfully,
Hans Herren says: "Today, I probably would not get the money for such
a big programme. Today, all funds go into biotechnology and genetic
engineering. The genetic people would try to construct a cassava that
is resistant against the mealy-bug. Biological pest-control, as we do
it here at the ICIPE, is not as spectacular, not as sexy. I see a big
problem here."

Scents against locust swarms

In the world of insects, scents play a major role not only as a means
of orientation (attracting and repelling 'road signs'). For insects,
odoursare the most important way of communication.

E.g. desert-locusts: since 10 years , Ahmed Hassanali and his team at
the ICIPE do research on the desert-locusts, more strictly speaking:
on their communication. The central question was: how and why do
harmless single locusts suddenly turn into most dangerous
swarm-locusts? What are the mechanisms of gregarisation and the
development of locust outbreaks? In general, desert locusts are
solitary insects. Over several generations, at particular times, they
build small swarms. Sometimes, they form bigger swarms, which can, all
of a sudden, turn into one huge swarm of as much as 40 billion
insects. In Madagaskar, in the years 1997/98, a swarm like this
destroyed the vegetation in an area of 1,4 million ha. For
ICIPE-scientists, odours were the key for the understanding of
swarm-formation. Hassanili and his group isolated and identified 5
different sets of chemical messages. These 'morse-codes' regulate
behaviour and life-style of desert-locusts. Some odours regulate the
behaviour in swarms of young and of adult insects, others determine
their behaviour of cohesion, the synchronous maturation, and the
communal oviposition. Another volatile chemical attracts the females
to their common egg-laying place.

At this point, the scientists intend to intervene: they exposed young
hopper-gangs to a very low concentration of odours from adult locusts.
The results were most fascinating: the hoppers became hyperactive;
they lost their orientation and began to cannibalise. The hopper-swarm
? shortly before a huge mega-organism -- fragmented into separate
parts. The swarm insects turned into solitary insects again, becoming
an easy prey for birds. Electrophysiological studies at the University
of Lund (Sweden) showed that the odours of adult insects blocked the
signal-transfer between the hoppers, resulting in a total loss of
communication between the individuals. "As if you cut the telephone
line", says Ahmed Hassanili.

The moment communication breaks down, nothing happens anymore. The
swarm is held together only by intense and constant communication
between the insects. The ICIPE now produces the volatile chemical in
larger quantities and hopes to test this method during the next
out-break. "This would be a very simple und extremely
environmental-friendly method", says Hassanili. "During the last big
plague 250 million$ were used exculsively for insecticides, 12$ pro
ha. We estimate, that with the odour-method costs will be at one
dollar pro ha at the utmost. And all this, without spraying toxic
insecticides and without longtime accumulation-problems."

Three other ICIPE projects, very briefly :

Tsetse-flies, the vectors for various fatal cattle-diseases, cause
yearly losses of 20 to 40% of all cattle in Africa. Buffalo- and
cow-urine turned out to be strongly attractive to the flies. With
these odour baits the flies can be lured into simple traps. ICIPE
scientists around scientist Rajinder Saini also developed a potent
repellent now being tested on cattle. Other repellents are being
isolated from body-scents of animals that are never attracted by
tsetse-flies (like the water buck).

Other tsetse-programmes: R&D of larvae-pheromones to attract
'pregnant' female-flies; behaviour-studies of the tsetse fly,
identification of tsetse-fly-hosts with ELISA-tests on blood-meals of
the flies; investigating traditional knowledge of tsetse-repellent

Neem-programmes: Development of natural pest control agents from the
neem tree (see also mail-out 76): Neem is being used locally to
control root-knot nematodes and fruit borers on tomatoes, aphids and
Diamond black moth on cabbage, it is being tested against leafminers,
banana weevils and ticks, for postharvest grain protection etc. We
visited a neem-nursery at the ICIPE: They grow 10'000 neem-seedlings
yearly and sell them cheaply to farmers. The responsible scientist is
Ramesh Saxena, lovingly called the "Neem-guru", and even his screen
saver shows a big floating NEEM-signature. ICIPE also developped
simple on-farm technologies for the preparation of neem 
and initiated a series of workshops on the use and raising of neem,
for farmers, womens groups and NGOs

Silkmoth conservation and utilisation: Breeding of a new domestic
silkmoth hybrid which produces a high quality silk, growing of
mulberry cultivars. The reeling of cocoons is done in a simple 
machine which can be  operated manually or by eletricity.This
sericulture (silkworm rearing) already today enhances the 
and economic returns of smallscale farmers and women's groups.

A survey of indigenous wild silkmoths in Kenya and Uganda has
identified 2 species, Argema mimosae and Gonometa spp., that 
silk fibres of

high quality; another 56 native species have been recorded in East
Africa, indicating a high diversity and potential for wild silk
production in this area. --- Articles, information on ICIPE and
biological pest-control: www.icipe.org and www.blauen-institut.ch

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