Copper sulphate inhibits Penicillium olsoniigrowth and conidiogenesis on Cannabis sativa

Fungal infections of Cannabis sativaare common and can severely affect yields, however, few studies have examined the use of fungicides for cannabis production. Copper (II) sulphate is an age-old fungicide that has been used to impede fungal diseases in multiple crops. This study aims to test the efficacy of copper sulphate against common cannabis fungal pathogens. Fungi were isolated from cannabis leaves and the most prevalent fungal pathogen obtained was Penicillium olsonii. P. olsoniiwas grown in vitroon potato dextrose agar (PDA) supplemented with various concentrations of copper sulphate (0–300 mg/L). The lowest concentration with a significant decrease in growth was 75 mg/L, while the half maximal effective concentration (EC50) and minimum inhibitory concentration (MIC) was calculated to be 73.1 mg/L and 474.9 mg/L, respectively. Healthy cannabis plants were inoculated with P. olsoniiand sprayed biweekly with copper sulphate (0 or 100 mg/L). After four weeks of foliar applications, genomic DNA was isolated from infected cannabis leaves and qPCR analysis showed P. olsoniilevels were significantly lower when treated with copper sulphate (100 mg/L) compared to the control. Conidia from infected leaves were isolated, stained, and counted. Copper sulphate treatment significantly reduced conidiogenesis compared to the control. This is the first report showing foliar applications of copper sulphate on C. sativacan reduce fungal disease and prevent the deterioration of cannabis yields.