Methyl bromide fumigation on exported cut Dendranthema grandiflorum L. affects postharvest qualities

As the top one cut flower in Taiwan, chrysanthemum (Dendranthema grandiflorum L.) was exported to Japan largely in nearly two decades. However, in recent years the chrysanthemum export to the Japanese market have decreased greatly due to neighboring competitors and other reasons. To have more opportunities for chrysanthemum growers, we explore new potential markets, and Australia is one of the ideal export markets for Taiwan's floral industry. Quarantine measurements for imported plants to Australia are required by the Australian government. But there is limited research about the effects of methyl bromide fumigation on cut chrysanthemum postharvest qualities. Therefore, in this study, two summer cultivars of cut chrysanthemum were fumigated with methyl bromide 32 g m for 2 h right before or after 48 h shipping simulation. Afterwards the quality of cut chrysanthemum during the vase period were investigated. Methyl bromide fumigation for 2 h killed pests, such as spider mites and thrips, nearly 100% on chrysanthemum 'Huang Chin Jen' and 'Bai Ten Shing'. However, fumigation caused early leaf wilting, especially the flowers in which fumigation occurred before shipping simulation completely lost commercial value. The vase life of flowers in fumigation treatment before shipping simulation was significantly affected, and the flower diameter also decreased with more than 30% compared to controls and flowers showed parts of browning florets. To sum up, to export good quality chrysanthemum, growers should strengthen production management and pest controls for better flower quality and therefore be more tolerant to fumigation. Better timing of fumigation is after shipping to Australia to avoid serious damage on cut chrysanthemum.