Diseases of Papaya PDF

Diseases of papaya S.N. Name of Diseases Causal Organisms 1. Papaya leaf curl disease Papaya leaf curl virus (PLCV) 2. Papaya ring spot virus Papaya ring spot virus 3. Papaya mosaic disease Papaya m...

Diseases of papaya S.N. Name of Diseases Causal Organisms 1. Papaya leaf curl disease Papaya leaf curl virus (PLCV) 2. Papaya ring spot virus Papaya ring spot virus 3. Papaya mosaic disease Papaya mosaic virus 4 Foot rot disease of papaya Pythium aphanidermatum 5. Anthracnose Colletotrichum falcatum Foot rot disease of papaya This is the severe disease, found in many parts of India. Causal organism: Pythium aphanidermatum It is a soil borne plant pathogen. Pythium is a genus in the class Oomycetes, they contain coenocytic hyphae (lacking cross walls), called a protist Symptoms It is characterized by the appearance of water-soaked patches on the stem near the ground level. These patches enlarge rapidly and girdle the stem, causing rotting of the tissues, which then turn dark brown or black. Such affected plants not tolerate strong wind and topple over and die. If the disease attack is mild, only one side of the stem rots and the plants remain stunted. Fruit if formed are shriveled and malformed. Gradually the plant dies. Disease cycle: Pythium aphanidermatum overwinters in the soil as resting spore (oospores), hyphae and/or sporangia. Oospores can germinates with help of germ tube and infect the plant directly, or, if the environment is favorable (that is an adequate amount of water is present), the oospore may produce sporangia, which in turn produce motile, biflagallete zoospores that swim through irrigation water throughout the field and easily reach to the host plant. It causes polycyclic plant disease. Favorable condition: Severe during rainy season on 2-3 years old plants; high moisture and temperature (36 0C), rainy condition favors the disease development. Management:  The soil should be drenched with 2-3 litres of copper oxychloride (3 g per litre of water). The application should be carried out regularly at 15 days interval from the time of planting.  Avoid water logging.   In the case of disease attack in existing crops, the rotted portion of the plant should be scraped and Copper Oxychloride or Bordeaux paste should be applied.  Seed treatment with thiram or Trichoderma viridae Papaya leaf curl virus (PLCV) This disease prevalent in several part of India. It was first time recoded in 1939 in Tamil Naduy by Thomas and later in Bihar, Karnatka, Kerala and Andhra Pradesh. Causal organism: This disease is caused by Papaya leaf curl virus (PLCV) a distinct monopartite species of the genus Begomovirus, family Geminiviridae. TYLCV has geminate particles which are isometric, 20 nm in diameter and genome as single-stranded circular DNA. The virus has an extensive host range. Symptoms Curling, crinkling and distortion of leaves, Reduction of leaf lamina, Rolling of leaf margins inward and downward just like inverted cup, thickening of veins. Leaves become leathery, brittle and distorted. Sometimes all the leaves at the top of the plant are affected by these symptoms. In advanced stages of the disease, defoliation takes place and the growth of the plant is arrested. Transmission and spread of virus The virus is mainly transmitted through by an insect vector the white fly (Bemesia tabaci Genn.) in a persistent-circulative non-propagative manner. It is also transmitting during the practice og grafting. High relative humidity and rainy condition favors the severe disease development in sick soil. Favourable conditions High relative humidity and rainy condition favors the severe disease development in sick soil. Management: Removal and destruction of virus affected plants and must be burned. Planting of disease resistance varieties reduces the disease incidence. Controlling the vector whitefly population minimizes the incidence of YVMV. Spray of neem product like Azadirachtin, neem oil at an 15 days interval reduces the white fly population up to the 79.2%. Imidacloprid 17.8 SL @ 1 ml/3 lit. or Thiomethoxam 25 WDG @ 1gm/3lit or Buprofezin 20 SC @ 2 ml/lit. or Ethiprole 20 SC @ 1 gm.lit. has been effectively controls the whitefly population. Spray every 14-21 days and rotate on a monthly basis with Abamectin so that the whiteflies do not build-up resistance to chemicals.