Apple scab disease

Class  Ascomycetes 
 Sub-Class   Loculoascomycetidae 
 Order  Pleosporales
 Family  Venturiaceae
 Pathogen   Venturiaceae inaequales 

Scab is rough ended ulsor or crust like on the on the plant parts. Apple scab is reported in those country where apple are grown. It is the most distractive cooled and humid climate.

Apple scab symptoms  

  1. First symptoms appear as olive brown spores on young leaf or flower bud.
  2. The spore soon turn to dark brown or black with variety appearance.
  3. As the growing lessons become older the velvaty appearance becomes brown and cracked.
  4. Crakes developed around luisons on the fruits. In reniour infection leaf may become dwarf and curly and eventually fell all.

apple scab disease, apple scab symptoms
Source: extension.umn.edu

Pathogen

  1. Venturiaceae inaequalis
  2. The young Mycelium haline but turn reddish brown with age.
  3. Dencely packed rounded Mycelium cells in several super imposed layer from stroma beneath the host cuticle.
  4. The shape of conidia are variable magening 6-9 micro × 12-20 micro
  5. Plasmogamy takes places through Antheredia and oogonia of compatible stains.
  6. Olive green to brown partially embedded perithecia appear generally in dead leaves.
  7. Such ascocarp are spherical 9-160 micro in diameter slitely pepepliate and ostiole and are surrounded by several setal of 25-75 micro in length.

Disease Cycle 

  1. The fungus survives the off season as stromatoid Mycelium in things of infected tree.
  2. The funguses perpetelate sepropectuly on follen leaves and twings. 
  3. Ascocarps are ejected forcibly into air and dis aminated by wind heavy ascocarps discharge is reported during the period of rain fall over 5-9 weak optimum temp.
  4. Ascospore germinates is 20°c.
  5. Conidia which are the source of Secondary enoculuon are dependent of water for dispersal and disamination.

Controls 

  1. Bordex mixture has been found to successfull control the disesase.
  2. Fungicides like capton glyodine ferban, thirman are recommended as coverspray against late infection.
  3. For ground spray fungicides like elgetol is suggested.