Phytophthora megakarya
Brasier & Griffin, is one of the Oomycete pathogens reported on
Theobroma cacao
, and it is the most virulent of the
Phytophthora
species that causes black pod disease.
Phytophthora megakarya was first reported as the causal agent of black pod disease in 1979 after the reclassification of
Phytophthora species recovered from infected cacao tissues. The pathogen causes pod rot, also referred to as black pod disease of
T. cacao, and is only endemic to West and Central Africa.
Phytophthora megakarya has spread westwards from Cameroon through Nigeria and Togo, to the major cocoa producing countries of Ghana and Côte d’Ivoire, and southwards to Gabon and Equatorial Guinea.
Phytophthora megakarya has become the main yield-limiting factor in cocoa production in the sub region, rapidly surpassing P. palmivora. The menace of
P. megakarya on cacao is of great concern to
P. palmivora
cocoa farmers and scientists, but the processes underlying the emergence of
P. megakarya on cacao are unknown. There is, thus, increased need for fundamental knowledge on the diversity and epidemiology of
P. megakarya in order to develop effective and sustainable methods for its control. This paper reviews the current state of knowledge on the origin, distribution and biology of
P. megakarya, in West Africa and evaluates the efficacy of current control methods. We highlight quarantine as a means of limiting the introduction of
P. megakarya into other cocoa growing regions, and also discuss cultural and biological control and use of resistant/tolerant varieties as major components of an integrated disease management strategy for the disease. The need for research into integrated management of the disease with emphasis on biocontrol and use of resistant varieties, and applying genomic information and tools from
T. cacao and from other Oomycetes for managing
P. megakarya are also discussed.
