SUGARCANE :: MAJOR DISEASE :: GRASSY SHOOT

Grassy shoot - Phytoplasma
Symptoms
The disease appears nearly two months after planting. The disease is characterised by the production of numerous lanky tillers from the base of the affected shoots. Leaves become pale yellow to completely chlorotic, thin and narrow. The plants appear bushy and ‘grass-like’ due to reduction in the length of internodes premature and continuous tillering. The affected clumps are stunted with premature proliferation of auxillary buds. Cane formation rarely occurs in the affected clumps, if formed, thin with shorter internodes having aerial roots at the lower nodes. The buds on such canes usually papery and abnormally elongated.

Pathogen
The disease is caused by a phytoplasma. Two types of bodies are seen in ultrathin sections of phloem cells of infected plants. The spherical bodies of 300-400 nm diameter and filamentous bodies of 30-53 mm diameter in size.
Disease cycle
The primary spread of the phytoplasma is through diseased setts and cutting knifes. The pathogen is transmitted secondarily by aphids viz., Rhopalosiphum maydis,Melanaphis sacchariand M. idiosacchari. Sorghum and maize serves as natural collateral hosts.
Management

• Eradication of diseased parts as soon as symptoms are seen.
• Avoid selection of setts from diseased area.
• Pre-treating the healthy setts with hot water at 52°C for 1 hour before planting

• Treating them with hot air at 54°C for 8 hours.
• Spraying the crop twice a month with insecticides.