Disease of Papaya
1.Stem rot / Foot rot – Pythium aphanidermatum
Water soaked spot in the stem at the ground level which enlarge and griddle the stem. The diseased area turns brown or black and rot. Terminal leaves turn yellow droop off. The entire plant topples over and dies. Forward by rain. R. solani is favoured by dry and hit weather. Common in 2-3 year old trees.
Mycelium is septate, brown and much branched. The sclerotia are black, spherical to irregular shape and produced in abundance.
Seed treatment with Thiram or Captan 4 g/kg or Chlorothalonil. Drenching with Copper oxychloride 0.25 % or Bordeaux mixture 1% or Metalaxyl 0.1%.
2.Powdery mildew – Oidium caricae
While mycelia growth appear on the upper surface of the leaf, flower stalks and fruit. Seven attak causes yellowing and defiation of leaves.
It is an obligate parasite. The mycelium is hyaline, septate and haustoria develop in epidermal cells. Conidia are hyaline.
Mode of spread and survival
The pathogen spread through wind borne conidia.
Spray Wettable Sulphur 0.25% or Dinocap 0.05% or Chinomethionate 0.1% or Tridemorph 0.1%.
3.Papaya ring spot – Papaya ring spot virus
Vein clearing, puckering and chlorophyll leaf tissues lobbing in. Margin and distal parts of leaves roll downward and inwards, mosaic mottling, dark green blisters, leaf distortion which result in shoe string system and stunting of plants. On fruits circular concentric rings are produced. If affected http://www.aipa.com.au/levitra-online/ earlier no fruit formation.
The virus particles are rod shaped and thermal inactivation point of the virus lies between 54 and 60˚C.
Mode of spread
Vectored by aphids Aphis gossypii, A. craccivora and also spreads to cucurbits not through seeds.
Raise papaya seedlings under insect-proof conditions. Plant disease free seedlings. Raise sorghum / maize as barrier crop before planting papaya. Rogue out affected plants immediately on noticing symptoms. Do not raise cucurbits around the field.
4.Leaf curl – Papaya leaf curl virus
Curling, crinkling and distortion of leaves, reduction of leaf lamina, rolling of leaf margins inward and downward, thickening of veins. Leaves become leathery, brittle and distorted. Plants stunted. Affected plants does not produce flowers and fruits.
Mode of spread
Spread by whitefly Bemisia tabaci.
Uproot affected plants. Avoid growing tomato, tobacco near papaya. Spraying with systemic insecticides to control the vector.
5.Anthracnose – Colletotrichum gloeosporioides
If affect leaf and stem on erotic spots are produced. On fruit initially brown superficial discoloration of the skin develops which are circular and slightly sunken. Then they coalesce in which sparse mycelial growth appear on the margins of a spot. Under humid condition salmon pink spores are released. Fruits mummified and deformed.
Mode of spread
Infection is caused by fruit from field. Secondary spread by conidia by rain splashes
Spray with Carbendazim 0.1% (or) Chlorothalonil 0.2% or Mancozeb 0.2%.