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Subject: [redesastres-l] Sistemas agroforestales de cacao: reducir plagas y enfermedades
Date: Tue, 07 Jul 2015 22:39:22 -0400
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Sistemas agroforestales de cacao: redistribuir la vegetación sirve  
para regular los ataques de plagas y enfermedades
Cocoa agroforests are complex agrosystems similar to natural  
ecosystems. That complexity is an asset in terms of managing cocoa  
pests and diseases. But how does it serve to regulate their presence  
and minimize the intensity of their attacks? Based on studies in  
Cameroon and Costa Rica, researchers from CIRAD and their partners  
recently demonstrating the predominant role of the spatial structure  
of such agroforests in terms of regulation.
Cocoa is one of the few plants still grown traditionally in  
agroforests in most producing countries. These cocoa agroforests are  
agro-ecosystems characterized by the substantial biodiversity of their  
vegetation, and also by considerable heterogeneity in terms of the  
spatial structure of their vegetation.
That complex structure makes them "similar" to natural ecosystems and  
enables them to render a range of ecosystem services. But what about  
pest and disease management? In other words, does that complexity  
influence the presence of cocoa enemies and the intensity of their  
To answer that question, researchers from CIRAD and their partners  
studied cocoa agroforests in Costa Rica and Cameroon.
Composition and spatial structure of agroforest plots
The researchers monitored three cocoa pests in particular, chosen for  
their contrasting spread and development characteristics.
In Costa Rica, they looked at frosty pod disease, caused by a fungus,  
Moniliophthora roreri,in a network of plots set up in the Talamanca  
In Cameroon, they observed black pod disease, caused by another  
fungus, Phytophthora megakarya, and mirids, bugs of the species  
Sahlbergella singularis that damage trees by feeding.
They began by describing the spatial structures of cocoa agroforests  
and building typologies. This enabled them to distinguish between  
different horizontal spatial structures, ranging from regular to  
clustered shade tree distribution.
The researchers went on to identify and rank, on an agroforest plot  
scale, the composition and spatial structure characteristics that  
affect the intensity of frosty pod disease attacks in Costa Rica and  
black pod and mirid attacks in Cameroon.
Regular tree distribution reduces attacks
This revealed the predominant role of the spatial structure of the  
plant stand in regulating pests and diseases.
In Costa Rica, frosty pod intensity increased the more the forest  
trees were clustered. In Cameroon, black pod incidence increased with  
the density of the understorey in the plot, and mirid attacks were  
less frequent the more regularly the shade trees were distributed.
These results can be put down to the numerous mechanisms that link  
vegetation structure to pests and diseases and the characteristics of  
those pests and diseases.
An initial step towards understanding natural pest and disease regulation
This study provided an accurate description of the structure of  
complex tropical agro-ecosystems and of the relations between the  
structures observed and pest and disease regulation.
January 18, 2021. Centro Nacional de Sanidad Agropecuaria, webmaster@censa.edu.cu .