Epidemiology, Epidemic Cost and Management of Cape Saint Paul Wilt of Coconut in Ghana

Few plants are as versatile as the coconut palm. Every part of the coconut palm; from the roots to the fronds and the many value-added products from them is useful to man [Ohler, 1999]. The coconut palm is a source of food and drink, folk medicine, receptacles, fibres braided into rope, frond roofs, and even fuel for cooking to millions of small holders. (Fig. 1) [Ohler, 1999]. The economic life span is estimated at 50 years, but the coconut palm can live for more than a century! [Bourdeix et al., 2005].

Globally, the coconut palm is economically important as a source of fats and oils and numerous industrial products. As far back as 1914, the coconut palm was the world’s leading source of vegetable oil, in terms of production volume and international trade.

In Ghana, an estimated 5.35% of Ghana’s population (estimated at 30.8 million in 2021) depends on coconut for their livelihood. The coconut palm is cultivated both as cash crop and as food crop. Its cultivation, processing and marketing offers employment to disadvantaged groups such as the landless poor, street children and rural women.

But Cape Saint Paul Wilt (CSPW), a lethal yellowing-type phytoplasmal disease has destroyed thousands of hectares of coconut plantations in the main coconut producing regions of Ghana namely, Western, Central, and Volta Regions. The disease can cause 100% crop losses if appropriate containment strategies are not implemented timeously. Typically, if infected, a one-hectare coconut farm (160 coconut palms) can die out within two years of manifestation of first disease symptoms, if no control measures are carried out. The capacity of the disease to decimate coconut populations in active disease foci threatens the coconut industry rehabilitation programmes in Ghana.

Hence, it is important to estimate crop losses from CSPW epidemic, quantify the losses in monetary value and determine the economic significance of crop losses from CSPW epidemics, to make a stronger case for the timely control of the disease in Ghana.

Control of diseases and pests of crops is critically important to increasing crop yields in agriculture. This is usually accomplished through elimination of the pathogen/pest or minimizing its effects on target crops by physical, chemical, biological and cultural means. Ideal disease control method of a high-value crop such as cocomut, must be efficacious, environmentally-save (minimum risk to the target crop, the farmer, and the environment, at and after production), easy to deploy and above all, affordable.

The modern approach to crop disease control is the integrated management of disease. Integrated disease management (IDM) relies on determination of the economic damage threshold (action threshold) and economic injury levels of a crop disease at which control measures should be initiated. The economic damage threshold is based on the economic ratio of benefit-to-cost. That is, the projected loss from a crop disease must be greater tha n the cost of containment measures, to justify control interventions.

The economic damage threshold approach to CSPW containment has proven largely unreliable in Ghana. Because, unlike insect pest infestation, where pest population or damage level can be monitored and controlled when the economic damage threshold is reached, CSPW is a vascular wilt, where symptoms represent advanced or terminal infestation. So, by the time control treatment is initiated based only on the appearance of disease symptoms, the irreversible economic damage has already occured.

Cape Saint Paul Wilt epidemic has a significant economic cost on coconut cultivation and yield in Ghana. But the economic cost of CSPW on coconut yield is lesser in hybrid coconuts, accentuating the knowledge that hybrid coconuts are less susceptible to the CSPW epidemic than the pure lines. This affirms Cape Saint Paul Wilt of coconut as an economic disease that must be contained, if not eradicated, through deliberate interventionist strategies such as aggressive scientific research,especially breeding research to maintain the profitability of coconut cultivation and its competitive position on the vegetable oils market.

This book is a two-fold compilation of the results of nearly 80 years of Cape Saint Paul Wilt of coconut research in Ghana. The first part details the major past scientific research interventions and achievements since the incetption of the CSPW epidemic in 1932; objectively evaluates current research efforts at containing the CSPW menace, and finally, makes an informed proposition on the future course of CSPW of coconut research in Ghana. The second part empirically demonstrates the economic cost of CSPW epidemic on coconut cultivation and yield in Ghana, using robust econometric models and statistical analytic tools.

My hope is to enhance global awareness of the economic importance of the coconut palm, eliminate farmer apathy in the commercial cultivation of coconut palm caused by CSPW epidemic, and ressucitate greater global funding for coconut research to revive the interest of scientists in coconut research. It is also my expectation that findings in this important book will constitute a strong basis to compel a comprehensive integrated management of Cape Saint Paul Wilt of coconut epidemic in Ghana, and beyond.