Survey and Exclusion Study to Explore for Natural Enemies in Ghana for the Control of Aerial Yam (Dioscorea bulbifera L.) in Florida, USA

A survey and exclusion study to establish the presence of D. bulbifera and its associated phytophagous insect fauna was conducted in Ghana between 2004 and 2006. The purpose was to identify potential biological control agents for this plant invading natural and protected areas in Florida, USA. The survey covered five regions based on herbarium records from three academic institutions in Ghana. A total of 40 phytophagous insect species in 9 orders were encountered on the plant with 24 species attacking D. bulbifera in two feeding guilds foliage and bulbil in Ghana. The impact of foliage feeding varied from species to species. The mean percent defoliation of aerial yam over all plots was 30%. Coleopterous species fed on only foliage and nearly all the leaves showed damage from these species. Anomala sp. and Adoretus sp. were the most important Coleoptera (Scarabaeidae) found feeding on the plant. Anomala species, exhibited a very narrow host range, attacking D. alata and D. bulbifera. Even though the damage it caused to aerial yam was relatively small, it exhibited very narrow host range. Lepidopterous species, mainly the Arctiid moths Diacrisia and Estigmene species attack aerial yam leaves and bulbils. They caused considerable damage to the bulbils the principal planting material. They however exhibited a wide host range attacking other Dioscorea species and therefore do not appear to be good biological control candidates.