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Current Status Of Lethal Yellowing Disease Of Coconut (Cocos Nucifera L.) In Grand Lahou, Cote D’Ivoire

Lethal yellowing was first reported in Grand Lahou, Côte d’Ivoire in 2013. The disease has destroyed 400 ha of coconut and caused loss of 1,200 tons of copra/year. The disease is currently threatening over 7000 ha and is severely affecting the livelihoods of smallholder farmers in Grand-Lahou. Symptoms include yellowing of oldest leaves to the youngest, early drop of seednuts, blackening of inflorescences, rotting of the apical bud, and death of the palm crown within 6 months after the symptom onset, leaving a bare trunk or “telephone pole”. A phytoplasma was identified based on the sequences of 16SrRNA and SecA genes as a member of the group 16SrXXII ‘Candidatus Phytoplasma palmicola’-related strains, subgroup –B, which exhibited a 99 % sequence identity with that of the Cape St. Paul Wilt Disease from Ghana. The CILY phytoplasma was detected in 82.9% of the symptom-bearing palms collected from all the surveyed villages, and trunk borings were recommended as the most suitable plant parts for sampling in Grand-Lahou. The phytoplasma was found in five botanical families identified as alternative hosts, which include Poaceae, Verbenaceae, Plantaginaceae, Phyllantaceae and Cyperacea. Five Hemiptera families were found as the most abundant within the fauna present in coconut plantations in Grand-Lahou, which include Aphrophoridae, Cicadellidae, Derbidae, Menoplidae and Tropiduchidae. A novel genus and species within the Erythroneurini tribe, family Typhlocybinae was identified as the potential vector of the disease. Ten coconut varieties have been selected for farmers for long-term trials in pilot farms to assess for their resistance to the disease. Eight plant clinics and ten field schools have been established in Grand-Lahou as the best approaches for information dissemination and to create disease awareness in the coconut-growing community. Results have been integrated within a new disease management plant that has been already made available for farmers to prevent disease spread.

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