Black pod disease
The pathogen can be greatly reduced if leaf litter is allowed to stay on the ground, otherwise, chemical control can be used for more severe cases.
White mycelia growth on lesions that appear several days after infection is a sign of the causal pathogen of black pod disease, which is Phytophthora spp.
The dispersal of sporangia or zoospores through water, ants and other insects occurs at this stage and will infect other healthy pods nearby.
[5] P. megakarya causes the same symptom as P. palmivora, but the occurrence is faster and generally produces greater amount of spores.
The seven species responsible for black pod disease are; P. capsici, P. citrophthora, P. megasperma, P. katsurae, P. palmivora, and P. megakarya.
[14] C. striatula was thought to be the most important vector that is responsible for black pod losses due to its building tent behavior as well as its dominancy within the area under particular condition.
In Ghana, C. striatula removes the outer layer of cocoa pod and uses this material to construct the tent.
Several other ant species namely C. africana, C. clariventris and C. depressa were also responsible for the spread of the disease besides C. striatula[14] In addition, Camponotus acvapimensis, another type of tent-building ant that uses soil as building materials for tent construction was identified as the most important agent to spread the inoculum in Nigeria.
Other invertebrates that were reported to be associated with spreading the disease are several species of beetle, snail, caterpillar and millipedes.
In addition, the cultivation of varieties that resistant to black pod is an alternative in order to reduce disease incidence.
Several cultural practices to manage black pod disease could be implemented in cocoa plantation.
In another study, the utilization of litter mulch under cocoa plantation has been reported in Papua New Guinea, which has some negative effect on the population of P. palmivora, and therefore could reduce the pod infection especially at the beginning of raining season.
Leaf litter showed rapid decline in pathogen recovery of colonized cocoa tissue after 18 weeks, relative to grass ground cover.
[16] An explanation for this is due to higher moisture content and microbial activity of other microbes under leaf litter that reduces the survival of Phytophthora cinnamomi as documented by Aryantha et al.
Metalaxyl (Ridomil) and cuprous oxide (Perenox) were identified to be successful in increasing the number of harvested healthy pod compared to the application of fosetyl aluminium (Aliete) and control treatment.
[7] In Ghana, a study that combined the sanitation and fungicide application showed a significant reduction in the percentage of disease incidence, where greater black pod incident were observed from pods on the trunk than the canopy in control treatment (no fungicide application).
[7] Heavy application of chemical fungicide eventually leads to resistance in pathogens and causes soil and water pollution.
Several species of fungi from the genera of Trichoderma were identified to be beneficial endophytes to control black pod caused by Phytophthora spp.
It was reported that moderate black pod cases (47%) occurred in the T. asperellum treatment compared to untreated trees (71%) and chemical fungicide (1.73%).
Numerous breeding programs have been established worldwide in order to screen and test local hybrids for resistance to Phytophthora spp.
[22] In addition, further work towards developing black pod-resistant varieties is being done by CEPLAC (Executive Plan of Cocoa Farming) agency in Brazil [23] and hopefully more breeding program focusing on black pod resistant will be established to produce commercialized resistant varieties.
