Pachymetra root rot

Pachymetra root rot is a devastating soil-borne disease caused by the oomycete pathogen Pachymetra chaunorhiza. This disease primarily targets the root system of the host plant, severely compromising its ability to absorb water and essential nutrients from the soil profile.

The primary and only significant host for this pathogen is sugarcane (Saccharum officinarum). Because the pathogen resides in the soil, it becomes a limiting factor in long-term sugarcane production, particularly in regions where intensive cultivation leads to a build-up of the pathogen's inoculum over time.

The disease manifests through various clinical signs in the field:

• Severe decay and browning of the primary and secondary root systems.
• Reduction in the overall root volume and mass.
• Stunted growth and chlorosis of the aerial parts.
• Increased vulnerability to drought and other environmental stresses.

The development and spread of Pachymetra chaunorhiza are heavily dependent on soil moisture levels. Zoospores require free water in the soil pores to swim and infect the susceptible root tips. Continuous monoculture of sugarcane exacerbates the problem, as the population density of long-lived oospores increases with each cropping cycle.

Management of the disease requires an integrated approach. Farmers are advised to utilize resistant sugarcane varieties, which is the most effective long-term strategy. Additionally, implementing rotation with non-host crops and ensuring proper soil drainage can significantly reduce the pressure of the pathogen in the field and minimize economic losses.