本研究篩選31種植物，以水浸方式取得水萃液，測試對黑斑病菌之抑制效果。其中，辣椒果實、刺芫荽葉片、福木果皮、柳橙果皮水萃液經高溫高壓滅菌處理後能抑制Alternaria alternata與A. brassicicola之菌絲生長，而且這4種植物水萃液可抑制A. brassicicola的分生孢子發芽，但僅有辣椒、刺芫荽、福木水萃液可抑制A. alternata的分生孢子發芽。提高植物水萃液濃度（至20%）對黑斑病菌菌絲生長及孢子發芽具更好的抑制效果。這些植物水萃液對黑斑病菌的影響，也透過評估菌絲細胞外導電率、菌絲細胞內容物滲漏、以及分生孢子細胞活性來作探討，結果顯示這些植物水萃液可傷害菌絲細胞使電解質滲漏、細胞內容物滲漏，並降低分生孢子的細胞活性。於甘藍幼苗接種試驗中顯示，施用20%辣椒與福木水萃液可預防或防治A. brassicicola所造成的甘藍黑斑病，未來可嘗試以辣椒及福木應用於植物病害管理。
A total of 31 plant extracts prepared by soaking the plants in water were evaluated for the inhibitory effects on Alternaria spp.. The autoclave-sterilized extracts of chilli (Capsicum annuum) fruits, culantro (Eryngium foetidum) leaves, common garcinia (Garcinia spicata) fruit rinds, and sweet orange (Citrus sinensis) fruit rinds inhibited the mycelial growth of A. alternata and A. brassicicola. The conidia germination rate of A. brassicicola decreased by the four plant extracts whereas that of A. alternata only decreased by the extracts of chilli, culantro, and common garcinia. An increase in the concentration (up to 20%) showed better fungal inhibitory effects. After plant extracts treatments, increasing extracellular hyphal conductivity, inducing cellular material release, and decreasing conidial cell viability of Alternaria spp. were demonstrated. The evidences may explain some of their antifungal mechanisms. Application of chilli and common garcinia extracts on cabbage seedlings produced comparable prevention and curative effects on black spot disease caused by A. brassicicola. The application of using chilli and common garcinia extracts on plant disease management would be studied in the future.