Study on the transmission of coconut Lethal Yellowing in Ghana

¹ CIRAD, Département BIOS, UPR29, P.O. Box 245, Sekondi, Ghana
² OPRI, Coconut Programme, P.O. Box 245, Sekondi, Ghana
³ CIRAD, Département BIOS, UPR29, Campus international de Baillarguet, 34398 Montpellier, France

^* rene.philippe@cirad.fr

Abstract

Research on the Cape Saint Paul Wilt Disease (CSPWD) vector in Ghana began from 1990 (1990-1997 ; 2002-2004) and did not give convincing results. From July 2005, new test standards were applied : shading, daily collections and releasing of insects at the less hot hours and use of various sizes of cages and test plants. More than 70,000 Myndus. adiopodoumeensis were introduced in cage for 28 months (520 adults/seedling/month). Controls in polymerase chain reaction (PCR) on the five coconut of this Myndus cage and on 935 adults were always negative. The tests of transmission with M. adiopodoumeensis apparently not a vector of the disease were thus stopped. The phytoplasma of the CSPWD was identified by PCR in a coconut having received 4,380 Diostrombus (four species of Derbidae) 4 months after the beginning of the test. This coconut never presented symptom of the disease 28 months later and all the successive PCR were negative. Auchenorrhyncha collected by sweeping on the adventitious plants in and around the plot during the day were also tested without success. The hypothesis of a ground transmission was also taken into account because of the presence of scale insects and nematodes.