The presentation by Dr. Gualbert Gbehounou (FAO) explains the concept of ecological weed management and outlines best practices to put it in practice at the farm level from Kenya and East Africa. The presentation builds on a Technical Guidance Document on “Mainstreaming ecosystem services and biodiversity in agricultural production and management in East Africa”, published by FAO in 2016, and was given at a national training workshops for stakeholders involved in the revision of the Kenya NBSAP that was held at ICRAF in Nairobi, 25-26 May 2016. More information on the event are available at: www.fao.org/africa/news/detail-news/en/c/417489/ The activities were carried out under the EU-funded project “Capacity building related to Multilateral Environmental Agreements (MEAs) in Africa, Caribbean and Pacific (ACP) countries – Phase 2” (ACP/MEAs2). © FAO: http://www.fao.org

1. Ecological Weed Management:
Ecosystem Services and Biodiversity
FAO Regional Policy Dialogue: Ecosystem Services from Sustainable Agriculture for Biodiversity Conservation Nairobi 24-26 May 2016
Gualbert Gbèhounou
FAO Strategic Programme 2 Management Team - Rome
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2. FAO Regional Policy Dialogue: Ecosystem Services from Sustainable Agriculture for Biodiversity Conservation Nairobi 24-26 May 2016
Farmers in Africa spend 20 – 60 % of their time weeding
their crops !
Delayed weeding due to labor shortage Maize crop destroyed by Striga hermonthica parasitism
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3. Weeds as major crop production constraint: prevailing vicious
weed circle in most African countries
FAO Regional Policy Dialogue: Ecosystem Services from
Sustainable Agriculture for Biodiversity Conservation Nairobi
24-26 May 2016
Labor shortage
Subsistence agriculture
Poor weeding
Weeds Low yield
Low income
Decrease of farm size
Migration
More pests (insects, rodents, pathogens)
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4. How does a weed population builds up ?
 Initial seed bank of a weed: St
 Mortality (dead seeds) : St * m (m in %)
 Germination (seedlings): St * g (g in %)
 Mortality seedlings : St * g * k (k in %)
 Weed population : St * g - St *g*k = St * g*(1-k)
 New weed seed production: St*g*(1-k)*f
 Seed bank at end cropping season: St+1 = (1-g-m) * St + f * (1-k) * g * St
 g, m, k and f are key variables that determine success of any weed
management method.
FAO Regional Policy Dialogue: Ecosystem Services from Sustainable Agriculture for Biodiversity Conservation Nairobi 24-26 May 20164

5. Ecological Weed Management
 Defined as: combination of methods aimed to achieve long-
term weed suppression through the use of ecological
interactions between crop, weeds, soil and/or other taxa
fostered by appropriate agroecosystem management with
the least possible use of direct weed control methods, e.g.
chemical or mechanical.
 It is all about ecologically acting on the variables g, m, k
and f to keep weed population under control.
 EWM is the best approach to weed management that
preserves ecosystem services making use of biodiversity!
FAO Regional Policy Dialogue: Ecosystem Services from Sustainable Agriculture for Biodiversity Conservation Nairobi 24-26 May 20165

6. Examples of Ecological Weed Management methods
 Cover crop and dead mulch from cover crop (Mucuna,
Acroceras, etc)
– Cover cropping effectively controls weeds by
increasing the mortality (k) of weed seedlings. It also
reduces soil erosion.
– Mulching:
 preserves soil moisture;
 reduces soil erosion;
 improves soil C/N ratio, thus stimulates population of soil
microorganisms and increases mortality (m) of weed seeds
and mortality (k) of weed seedlings.
FAO Regional Policy Dialogue: Ecosystem Services from Sustainable Agriculture for Biodiversity Conservation Nairobi 24-26 May 2016
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7. Dead mulching from Acroceras zizanioides vegetation effectively controls weeds
FAO Regional Policy Dialogue: Ecosystem Services from Sustainable Agriculture for Biodiversity Conservation Nairobi 24-26 May 2016
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8. Cover crop for weed suppression
FAO Regional Policy Dialogue: Ecosystem Services from Sustainable Agriculture for Biodiversity Conservation Nairobi 24-26 May 20168

9. Examples of Ecological Weed Management methods
 Trap cropping against Striga hermonthica
– Rotation with appropriate varieties of cowpea,
soybean, peanut, …. that induce suicidal germination
of Striga seeds thus induces high mortality (k) of
weed seedlings!
– Push-pull strategy for maize production using Napier
grass, Sudan grass, molasses grass and Desmodium
 Stimulates natural biological control of maize stem borers
 Stimulates suicidal germination of Striga seeds and high
mortality (k) of seedlings!
FAO Regional Policy Dialogue: Ecosystem Services from Sustainable Agriculture for Biodiversity Conservation Nairobi 24-26 May 20169

10.  Biological control of Invasive Alien plants: water
hyacinth (Eichhornia crassipes)
– The weevils Neochetina eichhorniae and Neochetina
bruchi effectively control water hyacinth;
– Unlike chemical control biological control of water
hyacinth restores biodiversity in infested water
bodies;
– Preserves quantity and quality of water resource.
FAO Regional Policy Dialogue: Ecosystem Services from Sustainable Agriculture for Biodiversity Conservation Nairobi 24-26 May 2016
Examples of Ecological Weed Management methods
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11. How can Ecological Weed Management be addressed in
NBSAP
 Preservation in seed banks and breeding for high performance
varieties of cover crops;
 Preservation in seed banks and breeding for high performance
varieties of trap crops of Striga;
 Inclusion of cover crops and trap crops of Striga in national seed
policy and seed value chain;
 Preservation and breeding for competitive crop varieties that reduce
weed pressure as done by AfricaRice for varieties of NERICA;
 Develop national capacity for production of bio-control agents of water
hyacinth and other invasive alien plants as done for example in Egypt
for management of water hyacinth.
FAO Regional Policy Dialogue: Ecosystem Services from Sustainable Agriculture for Biodiversity Conservation Nairobi 24-26 May 201611

12. Five principles for sustainable food and agriculture
Enhance the efficiency
of resource use
Conserve, protect, and
enhance natural
resources
Improve & protect
livelihoods and human well-
being
Enhance the resilience of people,
communities and ecosystems
Promote and improve
effective governance
FAO Regional Policy Dialogue: Ecosystem Services from Sustainable Agriculture for Biodiversity Conservation
Nairobi 25-26 May 2016
FAO Regional Policy
Dialogue: Ecosystem Services
from Sustainable Agriculture for
Biodiversity Conservation Nairobi
24-26 May 201612

13. FAO Regional Policy Dialogue: Ecosystem Services from Sustainable Agriculture for Biodiversity Conservation Nairobi 24-26 May 2016
Thank you!
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