Phytophthora megakarya is an oomycete plant pathogen that causes black pod disease in cocoa trees in west and central Africa.

[1] This pathogen can cause detrimental loss of yield in the economically important cocoa industry, worth approximately $70 billion annually.

Phytophthora megakarya's only known host is Theobroma cacao, or the cocoa tree, located in West and Central Africa.

It is considered to be the most virulent species of Phytophthora which infects T. cacao, causing the greatest percentage of yield loss.

[3] This pathogen causes black pod disease which produces an array of symptoms throughout the host’s life cycle.

P. megakarya is a facultative parasite that can infect any part of the cacao tree at any time under optimal environmental conditions.

[4] Other symptoms that may occur include damping off, dieback, lesions, mummification, premature drop, soft rot, and shriveling.

[7] P. megakarya is an oomycete that has a polycyclic disease cycle, producing three asexual spore types: sporangia, zoospores, and chlamydospores.

[4] A direct infection by the zoospore results in the production of more mycelia, which may develop into sporangia capable of releasing more inoculum or chlamydospores.

[4] These sporangia can be dispersed by rain, movement of planting materials, insects, rodents, and contaminated harvesting tools.

Like all oomycetes, zoospores produced by P. megakarya need free water on plant surfaces in order to encyst, germinate, and penetrate host tissues.

[11] During this time, moisture-laden air from the equator moves in, providing ideal moisture conditions for the growth of both cocoa trees and P.

[10] When the conditions are right, zoospores swim toward the surface of the soil where a fine aerosol is produced in the presence of water to transport the spores to the pods.

[11] In comparison to P. palmivora, P. megakarya is able to produce greater quantities of inoculum more quickly and can distribute it earlier in the season; thus it may infect more pods in a shorter time than P.

[1] Another form of cultural control is the burning of the pod husk piles to destroy additional sources of chlamydospores and sporangia.

[8] Through the examination and understanding of these processes, researchers can alter the genetic makeup of T. cacao trees in hopes of more effectively controlling the spread of black pod disease.

[16] As the trees age pod production decreases; warnings of chocolate shortages as soon as 2020 have been predicted based on the combination of these factors.