Economical and quick indexing of citrus greening disease in Sargodha, Pakistan

Citrus greening disease (CGD), a century old prokaryotic disease is one of the most destructive and widely distributed diseases in the citrus growing areas of the world. This disease has become a serious threat to citrus industry. Zinc spray gives a clue for the disease as persistence of symptoms even after the foliar application. The early detection of CGD is one of the key steps to manage the disease in time. Therefore, during a survey in 2018-2019, the study was carried out for routine, economical and quick detection of CGD in infected samples collected on the basis of symptomology. The samples were collected from the citrus orchards infected with greening disease. Iodo-starch test was performed to observe the accumulation of starch in the symptomatic leaves. Moreover, the infected bud-wood were grafted on healthy plants showed the mottling symptoms after 6-8 months. Dark grey edges of the infected leaves indicated the accumulation of starch. Among the five varieties as indicator, Sweet orange, kinnow and Feutralls’ early showed the mottling symptoms on indicator citrus plants. This confirmed the transmissibility of CGD and iodo-starch test was found reliable along with symptomology and vegetative propagation for early and quick detection of CGD. The iodo-starch test was effective as backed up by vegetative transmission.