Biological control of cacao diseases

This chapter discusses the advances in biological control of cacao diseases over the last 15 years. Most attention has been focused on biological control of frosty pod rot (Moniliophthora roreri), witches' broom (Moniliophthora perniciosa) and black pod disease (Phytophthora spp.). Research on biocontrol of other diseases in the cacao phyllosphere or rhizosphere is scarce or in its infancy. There is, however, a steady increase in information regarding the factors influencing and the mechanisms underlying biological control of cacao diseases as well as practical aspects such as inoculum production, formulation and application. There has been a clear shift away from inundative approaches using epiphytic BCAs towards more classical biocontrol approaches using bacterial and fungal endophytes as well as vesicular arbuscular mycorrhiza. These have the advantage that they can permanently establish themselves in the cacao tree. Moreover, besides direct competition for space and nutrients, antibiosis and mycoparasitism, through induced resistance and growth promotion, endophytes have a larger arsenal of mechanisms through which they can help protect their host. Endophytic BCAs could thus provide more effective and sustainable disease control. Recent advances in our understanding of the mechanisms through which endophytic biocontrol agents can reduce pest and disease impact provide possibilities for innovative disease control strategies, including combination therapies together with natural or chemical products. Continued work on production, formulation and application is also necessary in order for biocontrol to become economically interesting. However, biological control will not become a stand-alone solution for disease control but should become part of integrated pest management strategies, with cultural management as a central and reinforcing pillar. (Résumé d'auteur

Caractérisation des forêts mélangées

International audienceAn appropriate, common interpretation of stand structure characteristics is a key element to better understand forest ecosystem ecology and dynamics. Standards for characterizing the structure, dynamics and productivity of even-aged pure stands are well developed, but such harmonized concepts and methods for mixed forest stands are lacking. Here we compile a comprehensive set of measures, indices and methods at stand level to characterize and evaluate mixed stands. The chapter is organized according to the main components of the structure of forest stands; hence it includes (1) the most relevant concepts and approaches to describe stand density as a key component of stand structure; (2) stand species composition indicators and the most common species diversity indices used in the science of forest growth and yield; (3) how to describe tree distribution patterns, including horizontal spatial pattern, species intermingling and vertical spatial pattern, as well as species-specific height growth and canopy space partitioning; (4) ways to characterize tree-size distribution and growth partitioning among trees of different sizes; and (5) site productivity indices and methods for the comparison of productivity inmixed vs. monospecific stands. Finally we discuss some of the methodological and application challenges related to the reviewed indices and methods which require further attention