A tree-boring beetle the size of a sesame seed could cost South Africa $18.5-billion over the next decade as millions of urban trees are expected to die and will have to be removed and fruit, nut and lumber plantations are harmed, researchers estimate. The polyphagous shot-hole borer, which arrived in South Africa in 2012, has spread into eight of the country’s nine provinces with some infestations more than 1 000 km apart, researchers from Stellenbosch University and the University of Pretoria said in a study released this week.