Detection and Identification of Plant Diseases (AQA GCSE Biology): Revision Note

Plant pathogens

• Plants can be infected with a range of bacterial and viral pathogens; such as:

  • tobacco mosaic virus (TMV)

  • rose black spot fungus

• Plants can also be infested with insects such as aphids, which can infest a plant in large numbers and feed on phloem sap, weakening the plant

  • Aphids can also act as a vector for the transfer of plant disease

Detecting plant diseases

Higher Tier Only

• Detecting and identifying a disease allows effective treatment to be provided

• Plant disease is usually detected by observing visible symptoms:

Identifying plant diseases

Higher Tier Only

• There is some overlap between the symptoms of different plant diseases, making disease identification challenging; methods of identification include:

  • comparing symptoms to those described in gardening manuals or online

  • experts visiting an agricultural field or woodland to collect samples for identification in a lab

  • testing kits which contain monoclonal antibodies to identify the presence of pathogens quickly and easily

Mineral deficiencies

• Plant growth can also be affected by mineral deficiencies

• Plants may deficient in:

  • nitrates

  • magnesium

  • potassium

Nitrates

• Used in production of amino acids for proteins

• Symptoms of deficiency include:

  • stunted growth

  • upper leaves pale green

  • lower leaves yellow and dead

Magnesium

• Used in synthesis of chlorophyll; chlorophyll is needed for photosynthesis

• Symptoms of deficiency include:

  • yellowing leaves (chlorosis) due to a lack of chlorophyll

  • stunted growth.

Potassium

• Used in production of flowers and fruit

• Symptoms of deficiency include:

  • poor growth of flowers and fruit

  • yellow leaves

  • dead spots