Sorghum ergot

Sorghum ergot, caused by the fungus Sphacelia sorghi (the anamorph of Claviceps sorghi), is a significant plant pathogen that exclusively targets the floral structures of sorghum plants. This pathogen belongs to the Ascomycota phylum and is responsible for the disease commonly referred to as honeydew or sticky ergot in sorghum crops.

The fungus infects the ovary of the sorghum floret during the flowering stage, effectively preventing fertilization. Instead of normal grain development, the pathogen produces dense, fungal mycelial masses known as sclerotia. This leads to substantial reductions in seed yield, as well as the production of toxic alkaloids, rendering the remaining grain contaminated and unsuitable for consumption or livestock feed.

The disease cycle begins when conidia from contaminated soil or debris land on the stigma of a susceptible floret. Once infected, the floret secretes a sugary, sticky substance—the 'honeydew'—which is teeming with new conidia. Insects attracted by this fluid play a major role in the secondary spread of the pathogen, carrying spores from infected florets to healthy ones throughout the field.

Environmental conditions are critical for the successful infection and spread of Sphacelia sorghi. High relative humidity and moderate temperatures during the crop's flowering phase are the most conducive conditions for pathogen proliferation. Wind, splashing rain, and high insect activity further facilitate the rapid spread of the inoculum across the plantation.

Control measures primarily focus on integrated crop management. Farmers are advised to select hybrid varieties with shorter flowering periods, as this narrows the window of susceptibility. Proper crop rotation, eradication of alternate grassy weed hosts, and adjusted planting dates are essential practices. In severe outbreaks, the timely application of fungicides during the boot and flowering stages can help manage the incidence of ergot.

• The disease is characterized by white to pinkish sticky fluid on panicles.
• Sclerotia are the primary survival structures of the fungus.
• Ergot infection poses a significant threat to hybrid sorghum seed production.
• Early detection during the flowering period is crucial for effective control.