3.3.1 - Detection & Identification of Plant Diseases

How do aphids cause damage to plants?

• They use their sharp mouthparts to extract sap from the plant phloem, weakening the plant

• They are also vectors who can transfer pathogens from diseased plants to healthy plants

How can we reduce the number of aphids?

• Chemical pesticides

• Biological pest control - using ladybirds

Why do plants need a good supply of nitrate ions?

• Nitrate ions are required to convert sugars into proteins which are required for the plant to grow

• As a result, the growth of the plant will be stunted if there is not an adequate supply of nitrates

Why do plants need a good supply of magnesium ions?

• Magnesium ions are required to synthesize chlorophyll, which absorbs light energy during photosynthesis

• As a result, the leaves cannot photosynthesize properly and they turn yellow (chlorosis)

What are the symptoms of disease in plants?

• Stunted growth (lack of nitrate ions)

• Spotted leaves (e.g. rose black spot fungus)

• Decay/rotting

• Growths

• Malformation of stems/leaves

• Discoloration

• Presence of pests

What are three ways in which plant disease can be identified?

• Reference to a gardening website or manual

• Laboratory testing

• Monoclonal antibody test