Efficacy of Disinfectants Against Tropical Race 4 Causing Fusarium Wilt in Cavendish Bananas.

Fusarium wilt of banana (FWB), caused by a suite of Fusarium fungi, is among the most devastating plant diseases. The iconic FWB epidemic in the previous century lasted decades and was caused by so-called Race 1 strains that wiped out the dominant 'Gros Michel' banana plantations across Central America. Eventually, it was stopped because the Race 1-resistant 'Cavendish' banana variety replaced 'Gros Michel', which dominates global production (>50%) and trade (>95%). However, presently, the so-called Tropical Race 4 (TR4) threatens plantations of 'Cavendish' and many other banana varieties around the globe. Prevention is the first line of defense against the spread of TR4. Therefore, many disinfection units are installed to prevent the entry of TR4 in banana plantations. These foot and tire baths are filled with disinfectants, but limited knowledge is available on their efficacy. In this project, we evaluated 13 disinfectants commonly used in the Philippines. Our results show that the efficacy of these products depends on the type of fungal spores, the exposure time, and the replenishment frequency of the disinfection units. The resting spores of TR4 were resistant to all but one - unfortunately corrosive - disinfectant. Furthermore, we show that the actual contact time with disinfectants was far below the thresholds determined in laboratory experiments. Finally, muddy disinfection units reduced the efficacy of disinfectants. Taken together, we conclude that practices are inadequate to prevent the dissemination of TR4.