PAPAYA DIEBACK DISEASE

Papaya Dieback Disease is a very serious disease for papaya plants. It could destroy the papaya plant and lose the production of papayas up to 100%. This disease is a threat to the Malaysia’s papaya plantation industry. It has been a proclaimed as a danger disease under 1976 plant quarantine act. A papaya die-back disease was first reported in Malaysia by the Johor State Department of Agriculture in 2003. By the end of 2006 it had spread to five other states on the west coast of the Malaysian peninsula, affecting about 800 ha and resulting in the destruction of more than 1 million trees. Total yield losses were estimated at 200,000 metric tonnes, equivalent to US$ 58 million.

The varieties affected were Eksotika, Solo, Hong Kong and Sekaki. Early symptoms included yellowing and necrosis along leaf edges followed by water-soaked areas on the bases of leaf stalks, crowns and along leaf mid-ribs. Fruit symptoms included dark spots on the skin and water-soaked flesh. Later, necrotic and water-soaked areas developed on stems and spread to the internal tissues, followed by secondary fungal infections. In advanced stages bending of water-soaked leaf stalks occurs, leading to dieback, and death of trees. This article I like to share knowledge about Papaya Dieback Disease based on my own experience on indentification, diagnoostic and control measure during my tenure as District AO's in Johor.

From the literature, Hyaline bacterial colonies were consistently isolated on Luria Bertani agar from infected leaves, crowns, leaf midribs, fruits and leaf stalks after incubation for 48 h at 30°C. Isolates were Gram-negative rods, facultative anaerobes, oxidase negative and catalase positive. Six isolates were tested for tobacco hypersensitivity (Lelliot & Stead, 1987) and gave a strong response within 10-12 h. Pathogenicity was tested by inoculating suspensions into crowns and leaf stalks of five-month-old healthy papaya plants (cv. Eksotika). Sterile distilled water was used as a negative control.

Characteristic symptoms were observed one week after inoculation. No symptoms were observed on control plants. The original bacterium was re-isolated from symptomatic plants and one isolate was sent to a commercial service for 16S rRNA gene sequencing. The isolate was identified as Erwinia papayae based on BLAST analyses of sequences in the NCBI database, with the highest similarity to E. papayae (GenBank acc no: AY131237.1) from the Caribbean (Gardan et al., 2004). PCR using phytoplasma specific primers, P1and P7 (Guthrie et al., 1998) ruled-out the involvement of phytoplasma.

This is the first report of E. papayae causing papaya dieback in Malaysia. The disease may have entered Malaysia via Johor, then spread to other states by human activity and possibly birds and insects. The first report of this disease in S.E. Asia was in Java in (von Rant, 1931). E. papayae was first reported as causing bacterial canker of papaya in the Caribbean by Gardan et al. (2004).

DISEASE INFORMATION
Disease name : Papaya Dieback Disease
Patogen causes : Bacteria, Erwinia papayae
Parts effected : leaf, frond, shoot, bar and fruit
Ways to control : soil, water and no ways to control the papaya that has been infected by this disease unless the farmer practices good agriculture habit as the best way to prevent it.

SIGNS OF DISEASE
Papaya dieback disease attacks the entire parts of papaya plants including shoot, leaf, frond, bar and also the fruit. We can see clear signs on parts of the plants that have been infected by this disease. For the Shoot there is a sign of water-soaked and necrotic darkness on the part between shoot and frond. Gradually shoot will decay and lay down. For the Leaf there is water-soaked sign at the sides and at the end of the leaf. Leaf line and all along the leaf line will turn to necrotic darkness. For the Frond There is a sign of water-soaked and also necrotic darkness at the end of the frond. The leaf will finally lay down. Finally for the Bar there is is a sign of water-soaked at the infected papaya plants. The sympetom for the fruit are black spots at the fruit skin and the meat of fruit becomes water-soaked.

Healty papaya in Johore (Betik Sekaki)

Malaysia record 2,190 hectare of papaya plantation in 2007 ang the trend are increase to 2,861 hectate in 2008, 3,648 hectare (2009), 3403 Hectare(2010) and 3,512 hectare (estimate in 2011). The Malaysia papaya production allso increase from 36,937 metric ton in 2007 to 52,427 metric tones in 2011 (Estimated). The ability of agriculture department to deliver therir extension syatem and the role of papaya growers able to reduce the attack of Papaya Dieback Disease. Malaysia export papaya to China, Singapore, Wet Asia region and many other nations. Production of free papaya seedling for example able to reduce the attack of this disease significantly. I hope with the ability for the farmers to grow papaya following Good Agriculture Practice able to prodece high quality pepaya from Malaysia.

By,
M Anem
Ptjya
Malaysia
(Tengahari, 18 Ramadan)