Infertile soils, pathogens, pests, climate changes and other problems in many of the world’s cocoa growing regions are threatening the future of cacao production. Millions of small-scale farmers growing cacao using old-fashioned methods are incapable of meeting the challenge.
Cacao is considered an “orphan crop” – one of the last commercial crops to undergo an agri-technical revolution. Machinery, irrigation, fertilization, soil enhancement, plant protection and research are all far behind when it comes to cacao.
More than 80% of the world’s 5 million tons of cocoa is grown in the tropical belt by small-scale farmers. A typical family-run cacao farm encompasses 1 hectare (2.5 acres) with up to 1000 trees. Farmers use hand power and machetes, and outdated and poisonous copper-based fungicides. Research is being done by cocoa-dependent governments, various globally-scattered research facilities and groups, and within the laboratories of the large chocolate companies – but your average cacao tree in Ghana or the Côte d’Ivoire sees very little improvement.
Long-term production of cacao and inadequate nutrient inputs has led to serious depletion of soil fertility in the cacao producing regions of the world. Adding fertilizer can substantially increase yields, but there is a large variability in response, and in some cases, no discernable yield improvement. This is because yield depends not only on available nutrients but also on a whole suite of other factors: diseases and pests, water availability, soil type, shade, pruning, pollinating insects, competition with adjacent plants for resources, and more. The causal relations between these various factors, yields and fertilizer response, as well as the requirements of cacao for different nutrients, are poorly understood due to a sparse and narrow research base.
The cacao tree has little resistance to diseases caused by pathogens. Indeed, the main locus of cacao production shifted out of its indigenous area in South America because of two major pathogens: Moniliophthora roreri, which causes frosty pod, and M. pernisciosa, which causes witches’ broom. Newly encountered pathogens in West Africa include Phytophthora megakarya and P. palmivora, which cause black pod disease and are responsible for the greatest overall yield losses, and Cacao Swollen-Shoot Virus, CSSV, which causes swollen shoot disease and, within 3 to 5 years of infection, kills the entire tree. The cacao ecosystem also serves as a habitat for a wide variety of insect pests that adversely affect production, resulting in low yields. Important insect pests of cacao include mirids, stink/shield bugs, mealybugs, stem borers, termites, and the coreid bug.
Inadequate pollination also contributes to low pod yields, in part as a result of flower physiology and structure, and in part as a result of declining populations of pollinators. The rate of fertilization is quite low: only 1% to 5% of the total flowers. Conventional pollinators such as bees are not involved in cacao pollination because the flowers lack scent and nectar, and are physically very small. Moreover, while cacao flowers have both male and female parts, most cacao varieties are self-incompatible.
Cacao trees are sensitive to both drought and waterlogging, which is a function of the water holding capacity of the soil. In areas where there are extensive dry periods, a poor soil water holding capacity leads to water deficits, which cause large decreases in the rate of photosynthesis and lead to reduced yields. On the other hand, waterlogging during wet seasons can lead to inadequate soil aeration, prevent the initial growth and establishment of cacao seedlings, reduce pod production in mature trees, and promote soilborne fungal and fungal-like pathogens. The texture of the soil, whether sandy or clayey, has a strong influence on its ability to store and release water and nutrients.