The grassy shoot is a devastating disease that affects sugarcane, caused by phytoplasma. The disease is characterized by the formation of abnormal tillers, known as grassy shoots, which are characterized by excessive vegetative growth, reduced internode length, and narrow leaves with a pale green coloration.
Infected plants may produce up to 20 grassy shoots, reducing cane yield and quality. Stunted growth, abnormal tiller development, and tiny, narrow leaves indicate grassy shoots. Black hoppers, which feed on sugarcane phloem sap, spread the disease.
Chemical, biological, natural, and organic methods can control sugarcane grassy shoot disease. Insecticides stop black hopper disease spread. Lacewings and ladybugs are used in biological black hopper control. Resistant cultivars help manage grassy shoot disease naturally. Organic Black hopper control uses plant extracts and biopesticides like neem oil and Bacillus thuringiensis.
Grassy Shoot Management in Sugarcane
The Causal Organisms of Grassy Shoot Disease
Grassy shoot disease in sugarcane is caused by phytoplasma, bacterium-like organisms that can be transmitted via infected seed material (setts) and phloem-feeding insects such as leafhoppers and aphids. In infected plants, ultrathin sections of phloem cells reveal the presence of spherical bodies with a diameter of 300-400 nm and filamentous bodies with a diameter of 30-53 mm.
Dodder, a root parasite, can also serve as a transmission vector. The disease can also be mechanically transmitted via contaminated cutting instruments. The phytoplasma infects the phloem tissue of the sugarcane plant, causing unusual tiller development and a reduction in internode length. The disease can significantly reduce the yield and quality of sugarcane.
The Disease Cycle of Grassy Shoot Disease
Sugarcane, a grassy shoot disease, can survive and spread through various mechanisms. The principal transmission mode is infected seed material (setts), which propagates the disease via ratooning. The phytoplasma that causes the disease can also be transmitted via sap inoculation and contaminated cutting tools. In addition, phloem-feeding insects such as aphids and black hoppers serve as vectors for the disease’s transmission.
The root parasite dodder can also transmit the disease. The grassy shoot disease cycle involves the transmission of the phytoplasma via infected seed material and the propagation of the disease via ratooning. In addition to mechanical transmission, the disease can be transmitted via phloem-feeding insects and fodder.
Causes/conditions Favorable for Grassy Shoot Disease in the Field
Grassy shoot disease in sugarcane is mostly transmitted by planting infected setts. The black hopper insect (Browtista moesta) can also serve as a disease transmitter. Alternate hosts for the disease are sorghum and maize, and the symptoms can resemble those of iron deficiency, but only in random and isolated areas of the field.