In South Italy's Salento peninsula, plant scientists and environmental regulators tie a widespread epidemic of dying olive trees to a bacterium called Xylella fastidiosa. A polyvocal cohort of small landholders and environmental activists, however, contests this narrative. They claim that official attempts to stem epidemic spread by felling trees and spraying neurotoxic insecticides are guided by a "mafia science," whereby official diagnoses of tree incurability sow the ground for ecosystem destruction, land speculation, and agricultural intensification that will only benefit already wealthy business and property-owners. In turn, experts and the media dismiss activists' critique as "negationism" and their attempts to cure the olives as "witchcraft." Nearly 70 years ago, anthropologist Ernesto De Martino remarked that the Italian South was conditioned by a "crisis of presence." Magical thinking and intervention, he argued, represented tenuous modalities of wayfinding in an unstable world whose contours exceeded human capacity for manipulation. As centenary and millenary olives in Salento continue to wither, competing invocations of "mafia science" and "negationism" suggest that the peninsula's crisis of presence has extended in longue durée. Against efforts to read contemporary polemics over reality itself as features of a stalling liberal democracy, contested epidemic conditions might be more productively re-framed as morbid symptoms of an unequal agrarian economy that has endured centuries of change without undergoing lasting reform.