2103 - Plant Disorders and their Controls

Question 1

What is a Plant disorder?

Answer 1

Plant disorders are harmful disturbances of normal plant functions caused by environmental conditions.

Will have an Environmental, Genetic or Chemical cause.

• not contagious
• not infectious
• not caused by an infectious organism
• not a disease

Question 2

Plant Disorders - Frost

Answer 2

• light case. Yellowing or Browning leaf surfaces.
• Severe cases. Wilting, Scorch and Blackening of non woody stems. Especially young foliage.
• May lead to death of leaves, stems and even plant.
• Severe frost may rupture Xylem/Phloem is trees and shrub, splitting the bark and allowing for secondary infection to enter.

Question 3

Plant Disorders - Frost Control

Answer 3

• Follow correct hardening off procedure
• Avoid Frost Pockets
• Right plant in right place, not tender during cold spells
• cover at risk plants with fleece
• Glasshouses or Cloche
• Gas heaters

Question 4

Plant Disorders - Shade

Answer 4

• Etiolation, leggy plants, spindly growth reaching for light.
• Stems bending towards light
• Poor flowering/Fruit production

Question 5

Plant Disorders - Shade Control

Answer 5

• Right plant in right place
• Shade tolerant plants, Fatsia japonica
• supplementary lighting in glasshouse situation

Question 6

Plant Disorders - Drought

Answer 6

• Drying curling leaves
• Wilt in non woody parts
• Bolting in some root veg
• Growth will be reduced
• Flowering fruiting reduced
• Dieback or death

Question 7

Plant Disorders - Drought Control

Answer 7

• Drought tolerant species if prone
• irrigation system
• water when needed
• mulch to reduce water loss
• incorporate organic matter into the soil to improve water holding capacity

Question 8

Plant Disorders - Waterlogging

Answer 8

• Growth will stop or cease (anaerobic)
• Wilting, yellowing of leaves
• Root rot (Ethanol)
• Oedema on leaf surfaces (water pressure exerted through leaf tissue)
• Death

Question 9

Plant Disorders - Waterlogging control

Answer 9

• Plants adapted to boggy conditions (Lobelia cardinalis)
• improve drainage, or install drainage system (French drain)
• amend soil structure, if pan, caps etc are the issue

Question 10

Plant Disorders - Temperature Damage

Answer 10

• Plant can’t transpire
• scorching, bleaching, death of non woody stems and flowers
• wilting

Question 11

Plant Disorders - Temperature Damage control

Answer 11

• Shading, misting, dampening down
• Lowering temperature in glasshouse
• Do not expose plant to temperature extremes

Question 12

Plant Disorders - Soil pH

Answer 12

High pH - Calcifuge plants suffer lime-induced Chlorosis due to unavailability of Iron in the soil.
Yellowing of leaves, interveinal Chlorosis.

Low pH - Calcicole plants, Chlorosis.

Question 13

Plant Disorders - Soil pH Control

Answer 13

High pH

• mulch with pine needles
• feed with Sequestered Iron
• Add Sulphur chips to soil

Low pH
- add lime to raise pH

Plants right plants in the right soil pH

Question 14

Plant Disorders - Fasciation

Answer 14

Caused by hormonal imbalances in the meristem cells. Can also be cause by genetic mutations and infections.

Shoots, flowers misshapen and distorted.

• pest attack
• exposure to chemicals
• damage to plant growing tip (frost?)

Question 15

Plant Disorders - Fasciation Control

Answer 15

• avoid exposure to weed killers (drift)
• control environmental conditions where possible (cold, heat, insect attack)
• remove affected parts

Question 16

Plant Disorders - Rose Balling

Answer 16

Caused by excessive rainfall, generally late in the season.
Outer petals get wet and prevent the flower form unfurling.
Subsequently rots and falls off. (rot is not the disorder)

Question 17

Plant Disorders - Rose Balling

Answer 17

• Encourage good air circulation to promote drying
• Avoid watering roses from above
• cut back affected buts to prevent Botrytis