千日紅葉斑病於1998年於三芝鄉被發現，本病係由Nimbya gomphrenae 所引起，病原僅感染高彩及佛陀品種千日紅，對美洲千日紅並無病原性。美洲千日紅的葉片剛毛較長且密集，以至於露水可能不易附著於葉面，而成為減少病原感染的原因之一，而其葉片中的維管束較密集且間距較小，此也可能和增加其抗病性有關。孢子發芽後，會產生附著器或以菌絲直接穿透寄主表面，侵入寄主體內之後，菌絲穿透細胞(intracellular)生長，接種6天後，病原體又可自氣孔長出寄主體外。病原感染千日紅的溫度範圍為16～32。Ｃ，且以32。Ｃ發病最為嚴重。以胡蘿蔔洋菜培養基及V8洋菜培養基培養Ｎ. gomphrenae，可促使其產生大量的孢子。利用平板及液態培養篩選具有仰菌或殺菌效果之菌劑，以比芬諾(pyrifenox)較佳，噴灑10ppm pyrifenox於千日紅葉上即可顯著地（P=0.05）減少葉斑病的發生。
Leaf spot of globe amaranth was first noticed at San-chi villa, Taipei county in Taiwan in 1998. This disease was proved to be caused by Nimbya gomphrenae in this study. The pathogen infected Gomphrena globosa cv Buddy and cv Globosa readily, but not G. haageana cv Orange and cv Strawberry. This may be due to the difference of the leaf structures, i.e. intensity of vein, trichome and length of trichome. When spore suspensions were inoculated on the leaves of globe amaranth, conidia produced germ tubes and formed appressoria to penetrate into host directly. Infecting mycelia grew intracellularly and flourishingly within host tissue. Six days after inoculation, mycelia emerged from leaf surface through stomata. The temperature relevant for the infection of the pathogen ranged from 16 to32°C. High temperature (i.e. 32°C ) was favorable for the development of the disease. This pathogen sporulated significantly (P=0.05) more on carrot- agar and V8 medium than on other media. Screening of efficient fungicide in vitro, pyrifenox showed the best potential to inhibit the mycelial growth of N. gomphrenae. Spraying 10 pprn pyrifenox on leaves of globe amaranth reduced significantly (P=0.05) the development of the disease.
