Milo disease of sorghum

The first symptoms of Milo disease appear as chlorotic streaks on leaves, which gradually develop a characteristic reddish-brown discoloration.

Infected plants exhibit severe stunting and premature wilting, often leading to lodging during the grain-filling stage.

The root system becomes severely necrotic, causing the plant to be easily uprooted from the soil due to the destruction of lateral roots.

Cross-sections of the lower stem show distinct browning and disintegration of the vascular tissues caused by the fungal toxin.

Yield loss is evidenced by poorly filled grain heads and an overall reduction in seed weight and quality compared to healthy plants.

The causal agent of the disease is the fungus Periconia circinata, which is a soil-borne pathogen affecting various sorghum species.

The fungus survives in the soil and on crop debris for several seasons, acting as a persistent source of inoculum for subsequent crops.

It produces potent phytotoxins that are translocated systemically throughout the plant, causing necrosis far from the site of the root infection.

The pathogen primarily infects the root system, entering through natural openings or wounds created by pests or cultural practices.

Periconia circinata belongs to the group of mitosporic fungi that are highly adapted to surviving in hostile soil environments.

Warm temperatures, generally between 25 and 30 degrees Celsius, combined with adequate soil moisture, favor the rapid development of the fungus.

Soil conditions such as high salinity or compaction increase plant stress, making sorghum significantly more susceptible to Periconia circinata.

The concentration of the pathogen in the soil increases dramatically under continuous cropping systems where no rotation is practiced.

Poor soil aeration can exacerbate the disease progression by weakening the plant's overall defense mechanism against soil-borne pathogens.

High humidity during the early growing stages promotes the initial colonization of roots by the fungus.

The primary economic impact is a dramatic reduction in grain yield caused by the premature death of the plant before maturity.

Infected fields often show a patchy appearance, which creates logistical challenges during harvesting and reduces overall field uniformity.

The toxin produced by the fungus limits the plant's ability to transport water and nutrients, resulting in lightweight, shriveled grains.

Severe outbreaks can lead to total crop failure in specific zones, requiring expensive replanting or conversion to less sensitive crops.

Plant vigor is severely compromised, making the crop unable to withstand drought or secondary opportunistic infections.

The most reliable control measure is the use of resistant sorghum hybrids that have been specifically bred for tolerance to Periconia circinata.

Crop rotation remains the cornerstone of integrated disease management, preventing the build-up of fungal inoculum in the soil.

Proper soil management, including the deep plowing of crop residues, helps in breaking the pathogen's life cycle by accelerating decomposition.

Seed treatment with systemic fungicides can provide essential protection to seedlings during the critical early stages of development.

• Maintaining optimal soil fertility to boost plant defense
• Managing root-feeding soil insects that cause wounding
• Avoiding waterlogged soil conditions to prevent secondary rot