The document discusses learning objectives about identifying healthy plants and common plant pests and diseases. It provides details on signs of healthy plants, why aphids and slugs are pests, and what damping off and potato blight are. It also discusses how lack of nutrients, too much water, and fungi can impact plant health and how to control pests, viruses, and fungi in greenhouses.

1. Learning Objectives:
• What are the signs of a healthy plant?
• Why are aphids and slugs pests?
• What is damping off and potato blight?
• How can pests, viruses and fungi be controlled
in glasshouses?

3. Poor answers:
 It has a good colour
 It has flowers
 It looks good
Better answers:
 Leaves are a dark green colour
 It has lots of brightly coloured flowers
 There are no signs of pests of diseases

4. Plants lose water all the time
through their stomata during
transpiration.
Transpiration is quickest if:
• it is warm
• it is dry
• it is windy
If the plant loses too much water
then the leaves will become flaccid
and wilt.
Wilted leaves cannot absorb light
and so cannot photosynthesise or
grow.

5. Some pests such as slugs and caterpillars
eat leaves so there is less area for
photosynthesis.

6. Aphids have long, tubular mouthparts which they use to suck sucrose from the
phloem. This reduces the amount of sugar available to the plant for respiration
and therefore energy.
Aphids can also transmit viruses from one plant to another.
Aphids can be controlled by spraying with
insecticide or using biological agents.

7. Lack of nutrients can
lead to leaves becoming
discoloured and reduced
photosynthesis.

8. If soil is too damp or
the air is too humid,
seedlings can get a
fungal disease called
damping off. The
seedlings fall over
and white mould can
be seen at the base
of the stems.
To prevent this, do not
overwater seedlings
and ensure adequate
ventilation.

9. This is caused by a fungi which can also infect
tomatoes.
Fungal spores are spread through the air and it is
most likely to occur when the weather is warm
and humid.
The leaves will start to develop brown patches.
Tubers will have brown patches on their skin and
the inside becomes brown and soft.
To prevent the diesase spreading remove and
burn infected leaves and spray with a fungicide.
Resistant varieties can be grown.

10. Only grow good quality seed potatoes to prevent spreading the disease.