First Report of Macrophomina phaseolina Causing Charcoal Rot of Cucumber in Indiana

Macrophomina phaseolina is the causal agent of charcoal rot on more than 500 plant species. Most reports of this disease are from agronomic crops such as corn, cotton, sorghum, and soybean. Most reports of this disease are from agronomic crops such as corn, cotton, sorghum, and soybean. To date charcoal rot of cucumber (Cucumis sativus L.) has been reported in Illinois and Pakistan. In June 2018, several ‘Tasty Jade’ cucumber plants in a Purdue University research high tunnel in Vincennes, IN, developed wilt symptoms. The symptom was identified to be caused by Macrophomina phaseolina. To our knowledge this is the first report of M. phaseolina causing charcoal rot on cucumber in Indiana. M. phaseolina is known to be favored by high soil temperatures such as would be observed under black plastic mulch in a high tunnel. This report is significant both because it is the first report of charcoal rot of cucumber in Indiana and because it appears to be the first report on cucumber in the United States in over 50 years.