During packing we were still checking all the pears for injuries ("stem punch", caused by other pears), since apparently it would spoil the whole box if there was a bad one. (Packing pears in New Zealand for export to Europe and the US) - On a commercial and longterm scale you apparently still have to take care.
Rotting fruits release ethylene gas which is a ripening agent. This causes fruit next to rotting fruit to ripen then rot.
An interesting mechanism I think. Before looking that up I would have suspected a biological transmission of infection or something, not a chemical transmission.
