Plant nutrition affects plant diseases and epidemics development. The effects of supplemental nitrogen, potassium and calcium on white mold susceptibility in sweet basil were tested in pots and under commercial conditions. An increased concentration of N in the irrigation solution increased the N content of shoots, which led to higher susceptibility to white mold on cut shoots in a linear manner. Increased levels of K in the irrigation solution and in the sweet basil tissue resulted in an exponential decrease in the severity of white mold on cut shoots. Likewise, foliar application of K also significantly decreased white mold susceptibility. Lower K fertigation under commercial-like conditions significantly increased susceptibility to S. sclerotiorum infection. Calcium decreased disease susceptibility, but there was no additive effect when Ca was added to the K treatment. Combining Ca and K fertigation with foliar-applied KCl and fungicide (boscalid + pyraclostrobin) provided synergistic lower disease on cut shoots. The K spray was not as effective as the fungicide for suppressing disease. In conclusion, proper K fertilization and the application of Ca can significantly reduce the susceptibility of sweet basil shoots to S. sclerotiorum and may be integrated into management programs for proper disease control. © 2019, Springer Nature B.V.