plant disease and defences

• Plant diseases


  Caused by microorganisms including fungi, bacteria, viruses, and larger organisms like insects
• Deficiency diseases


  Caused by lack of essential minerals like nitrates or magnesium ions
• Nitrate deficiency


  • Stunted growth, not growing as much as they should
• Magnesium deficiency


  • Chlorosis (lack of chlorophyll), yellow leaves
• Symptoms of diseased plants

  • Abnormal growths or lumps
  • Malformed stems or leaves
  • Patches of decay
  • Spots of discoloration on leaves
• Diagnosing plant disease


  1. Take basic observations

  2. Match symptoms to a disease listed in a garden manual or website

  3. Send sample to plant pathologist for more detailed testing
• Plant pathologist


  Specialist in plant disease who can do more detailed testing
• More basic method of diagnosing plant disease

  1. Trial and error

  2. Try one treatment and see if it fixes the issue
• Plant defenses


  • Physical
  • Chemical
  • Mechanical
• Physical defenses


  • Waxy cuticle, cell walls, layers of dead cells (bark)
• Chemical defenses


  • Antimicrobial substances, poisons that deter or kill insects
• Mechanical defenses


  • Thorns, hairs, leaves that curl or droop
• Many drugs are derived from plant chemicals, including aspirin from willow trees