Concert promoters in South Africa pulled the plug on a tour featuring Ludacris, Trina and Kelly Rowland, citing poor ticket sales.Promoters of the Summer Vibes Tour cancelled shows in Cape Town and Durban, blaming poor attendance at Friday’s concert at the Dome in Johannesburg.Barry Florence, the tour’s promoter, said he had to cancel the shows, citing the Johannesburg shows as an indication of what was ahead.”Advance sales in Durban and Cape Town are low, suggesting that attendance in those cities will not be much different to Johannesburg,” Florence told South Africa’s Independent newspaper.Florence said fans can get full refunds for their tickets at the nearest Computicket.