Diseases of Ginger and Turmeric

Microbial pathogens are major agronomic constraints in the cultivation of zingiberaceous crops like ginger and turmeric, especially in small and marginal farm holdings. Ginger production is affected by all major pathogen taxa belonging to Oomycetes, fungi, bacteria, and viruses, whereas turmeric is predominantly impacted by fungal and oomycetes pathogens. The soil-borne diseases directly impact the production of economic products, the rhizomes and their innate quality, and are a perennial threat and recurrent yield-limiting factors. Pathogen-supporting propagation material and poor implementation of rhizome health management practices have emerged as major reasons for continued crop losses in all major production regions in the world. Coupled with climate change compounding pre-harvest production issues, ginger and turmeric cultivation practices need calibrated-technological interventions. In tune with scientific advancements in general, our understanding of plant pathogens affecting ginger and turmeric too has enhanced significantly over the decades. The onset of the genomic era in the late twentieth century has also left its mark on the pathogens that impact ginger and turmeric. The public availability of genomic resources of plant pathogens such as Pythium, Ralstonia, and fleck virus affecting ginger and their host-interactome has opened up new opportunities to unravel the mode of pathogenesis and host resistance mechanisms. While chemical disease management methods have proven effective and are often recommended, their continual use in commercial horticulture is being scrutinized due to concerns about their perceived environmental impact, as indicated by the restricted usage or outright bans on numerous fungicides. Furthermore, the growing awareness about chemical (residue) free clean spices for trade and human consumption has renewed the search for alternative methods of disease management. To that effect, policy initiatives for seed rhizome production in disease-free areas with due certification procedures for rhizome health are essential. Technological interventions for rhizome treatment can be another strategy. The untapped diversity within the microbiomes of ginger and turmeric presents an opportunity for utilization in eco-friendly and sustainable spice production systems. This chapter compiles and discusses the current state of diseases affecting ginger and turmeric, covering aspects such as the causal pathogens, pathobiology, epidemiology, and available disease management strategies.