1.3 The need to understand and address cocoa pest issues and their management

In many cocoa growing areas, major constraints to production include the black pod diseases (Phytophthora spp.) and farmers spray on a regular basis, since copper compounds and other fungicides are efficacious [1]. In contrast, two fungus diseases, belonging to the genus Moniliophthora, pose a significant threat to the crop in Latin America where they are thought to have co-evolved with cacao and other plants in the tribe Theobromateae, making control much more difficult.

The work of the Angiosperm Phylogeny Group (APG4) might appear rather academic, but it can also have practical significance, including importance for cultural control methods. These remain the foundation of IPM strategies for most crops, not least the pest complex associated with the cocoa plant, Theobroma cacao. 

Cultural practices are discussed in more detail elsewhere (national recommendations and general guides [2]), but minimising pesticide use must inevitably be linked to the cultivation of a healthy crop, with serious attention paid to potential alternative hosts and other phytosanitary measures (Chapter 7). 

As cacao was introduced to Africa and Asia, a number of ‘new encounter’ diseases and insects, such as mirids, rapidly became prevalent as countries adopted the crop. Table 1.2 summarises the key pest problems, with Phytophthora black pod especially important and possibly subject to the most global pesticide use for the crop. P. megakarya has only been found to occur in Central and Western Africa and has been isolated from many different plant species but does not appear to cause any significant symptoms, and to date the original forest host has yet to be identified [3]. 

Cocoa swollen shoot virus disease (CSSVD) is thought to have arisen from Adansonia, Ceiba, Cola and Sterculia – all in the Malvaceae; reclassification shows that “potential alternative hosts” may have to be placed at the family level or beyond. 

The science associated with these key problems is subject to continuous review, from several routes of enquiry. Likewise, it is probably no coincidence that the major cocoa ‘capsid’ (Miridae) pests, prevalent in different regions, all come from very closely related genera (in the tribe Dicyphini) and usually oligophagous to Malvaceous plants.

Pesticides have now been used on cocoa for more than 60 years, with notable early research carried out independently in the former West African Cocoa Research Institute (now the research institutes of Ghana and Nigeria), Brazil, Ecuador, Cameroon, Costa Rica, Côte d’Ivoire, Indonesia and Malaysia.

By the early 1970s, a number of effective control techniques had become ‘established’, and there was little incentive for change until environmental awareness increased in the 1990s. Notable amongst these were concerns over the widespread use of lindane for the control of cocoa insect pests; this chemical was eventually phased out but not until the early 21^st century in some countries. Many farmers believe that pesticides work, at least against some cocoa pest problems, and continue to use them depending on the pest and country (Table 1.2).

Table 1.2 A guide to cocoa pests against which pesticides may be in current use (based on industry sources and the author’s observations).

Key: 

1: Common (although not necessarily ubiquitous) use of pesticides: often dependent on economic circumstances of farmer
2: Localised use of pesticides (may be frequent if cocoa grown commercially)
3: Pesticide use rare, ineffective or experimental: cultural and other control methods recommended.