Rhizome rot of ginger ( Zingiber officinale ) caused by Pythium myriotylum in Fiji and Australia

Observations on the etiology of rhizome rot of ginger are presented for Fiji and Australia. In Fiji, the disease generally develops during hot, wet conditions in March and April, and often causes losses of more than 50% in seed crops. In Australia, the disease was observed for the first time during the wet summer of 2007–08, almost totally destroying the immature ginger crop in one field and causing 8–30% losses in other fields. Measurements taken when soils were saturated due to almost constant rainfall indicated that many plants died within 3 weeks of showing the first signs of yellowing, with the disease spreading down slopes at rates of up to 4.5 m/day. Pathogenicity tests indicated that the disease was caused by Pythium myriotylum and that the pathogen was capable of destroying ginger rhizomes in 1–2 weeks in saturated soils at temperatures of 26–30°C. The role of the environment in exacerbating the disease is considered and implications for management are discussed.