Johnsongrass mosaic

Johnsongrass mosaic is a plant viral disease caused by the Johnsongrass mosaic virus (JGMV). The pathogen belongs to the Potyviridae family and the Potyvirus genus. As an obligate parasite, the virus relies on living host tissues to replicate and spread, primarily impacting plants within the Poaceae family.

The primary hosts for this virus are sorghum (including Sudan grass), maize, and wild species such as Sorghum halepense (Johnsongrass). Infection is characterized by distinct mosaic patterns on leaves, ranging from mild chlorosis to severe streaking, often accompanied by stunted growth and reduced vigor of the host plant.

The biological cycle of JGMV is highly dependent on aphid vectors, such as Rhopalosiphum maidis. The virus is transmitted in a non-persistent manner, meaning aphids can acquire and transmit the virus within seconds of feeding. In temperate regions, the virus persists primarily in the rhizomes of Johnsongrass, serving as a primary inoculum source for new crops.

Environmental conditions that favor the proliferation of aphids significantly increase the risk of disease outbreaks. Warm, dry weather usually accelerates vector activity and movement, leading to rapid secondary spread throughout a field. Early infection of younger plants typically results in more severe economic losses.

The economic impact involves significant reductions in biomass, grain yield, and forage quality. Management strategies focus on breaking the disease cycle:

• Aggressive management of Johnsongrass to eliminate the primary viral reservoir.
• Utilizing resistant or tolerant crop varieties.
• Implementing insecticide programs to control aphid vector populations.
• Establishing adequate spatial isolation from known infected areas.