Plant Disease

• Tobacco Mosaic Virus

  A virus that affects plants. It causes stunted growth and causes leaves to discolour, curl and have yellow streaks or spots.

  
• Rose black spot


  A parasitic fungus that causes black spot on roses.

  
• chlorosis

  Yellow leaves caused by a lack of magnesium which is needed to produce chlorophyll.

  
• Plant physical defences

  Layers of dead cells around stems

  Tough waxy leaf cuticles

  Cellulose cell walls

  
• Plant mechanical defences


  Thorns or hairs

  Leaves that droop or curl when touched

  Mimicry

  
• Plant chemical defence


  Production of antibacterial chemicals

  Production of poisons

  
• How does black spot fungus affect the growth of roses?

  Damaged leaves cannot photosynthesise efficiently.
• How is rose black spot treated?

  Removing infected dropped leaves and burning them.

  Pruning shoots in the spring.

  Treating infections with fungicides.
• How is rose black spot transmitted?

  The fungus produces spores which are released in wet, humid conditions.
• How can plant diseases be identified?

  Stunted growth.

  Spots on leaves.

  Areas of decay.

  Discolouration.

  Presence of pests.