Major and minor diseases
Correct diagnosis is important because yellowing, drying and tiller collapse can result from pathogens, poor drainage, root injury, drought, nutrient imbalance or pests. Inspect the collar, rhizome, roots, pseudostem, leaves, panicles and capsules.
Cause: Phytophthora nicotianae var. nicotianae and/or P. meadii
Symptoms: Water-soaked lesions on young leaves or capsules; necrosis and shredding; immature capsules decay and fall; panicle-tip infection moves downward; severe cases reach rhizomes and tillers.
Favouring conditions: Most severe with continuous rain, excess moisture, thick shade, overcrowding and infected soil. Malabar may be more severely affected.
Management focus: Regulate shade and spacing, remove diseased material and mulch from the base, ensure drainage, and use approved preventive sprays/drenches or biological agents as locally recommended.
Cause: Pythium vexans and Rhizoctonia solani
Symptoms: Yellowing and decay from the collar; rot extends into rhizomes and roots; affected tillers fall with slight disturbance; severe infection kills the clump.
Favouring conditions: Monsoon, excess soil moisture, poor drainage and high soil inoculum.
Management focus: Sanitation and drainage are central. The guide combines plant sanitation with copper oxychloride or other approved rot management and Trichoderma/Pseudomonas at separate intervals.
Cause: Fusarium spp.
Symptoms: Yellowing; round to oval brown pseudostem lesions that elongate and deepen; brittle breakage; root-tip rot and dieback; lower leaves and panicle tips dry.
Favouring conditions: Often appears toward the end of monsoon and becomes prominent in dry, exposed or stressed plots.
Management focus: Cover exposed roots, mulch, irrigate during dry periods, maintain shade, clean before monsoon and apply biological or approved protective treatments.
Cause: Colletotrichum gloeosporioides
Symptoms: Water-soaked lesions coalesce into yellow-brown to reddish-brown patches. Leaves eventually dry and plants may look burnt.
Favouring conditions: Often severe in the post-monsoon period.
Management focus: Destroy affected debris, retain 40-60% filtered light and use preventive disease management before and after monsoon as locally advised.
Cause: Phaeodactylium alpiniae
Symptoms: Round water-soaked leaf lesions, roughly as wide as the lamina; cottony mycelial growth can be visible on the lower surface.
Favouring conditions: Rainy season and excessive shade.
Management focus: Improve shade management and apply preventive protection before and during monsoon where disease history warrants it.
Cause: Sphaceloma cardamomi, Cercospora zingiberi and Phakopsora elettariae
Symptoms: Spherical blotches, rectangular muddy-red stripes along veins, or whitish powdery pustules below leaves with yellow necrotic patches above.
Favouring conditions: Nursery and field conditions vary by pathogen.
Management focus: Remove affected material, improve aeration and apply locally approved disease protection if needed.