Use of Immune Crops as Barrier in the Management of Cacao Swollen Shoot Virus Disease (CSSVD)—Long-Term Assessment

Abstract

A field trial was conducted at the Cocoa Research Institute of Ghana from 1992 to 2004 to investigate the prospects of using Cacao swollen shoot virus (CSSV)-immune crops as a barrier to prevent the spread of the virus from existing outbreaks into newly established cacao plantings. The treatments consisted of four crops—citrus (Citrus spp.), oil palm (Elaeis guineensis Jacq.), kola (Cola nitida Vent.), and cacao (Theobroma cacao L.)—planted as a barrier between cacao trees serving as test plants on one side and as source of CSSV strain 1A infection on the other. Over a 7-year period post CSSV 1A inoculation, the citrus and oil palm barriers were the most effective in protecting test cacao trees from cacao swollen shoot virus disease (CSSVD) spread. The two crops gave comparable results (P = 0.9766) in terms of the cumulative number of visibly infected trees (1 and 5 of 522, respectively). The kola barrier, on the other hand, had a significantly (P < 0.000l) higher number of symptomatic trees (89 of 522) than citrus and oil palm. All three crops (citrus, oil palm, and kola) provided better protection than the control (cacao), which had 134 visibly infected trees out of 522. As shown by economic analyses, growing citrus, oil palm, or kola as barrier crops was as profitable as growing cacao. The implications of the results on the management of CSSVD in Ghana are discussed.