(a)(i) Define vegetative propagation. [2 marks]
(ii) Give three advantages and three disadvantages of vegetative propagation. [6 marks]
(b) State four cultural methods used for controlling crop pests in the field. [4 marks]
(c) Enumerate four harmful effects of chemical pest control. [4 marks]
Explanation
(a)(i) Definition of vegetative propagation Vegetative propagation is the use of plant parts other than seeds to produce the subsequent generation of plants (ii) Advantages and Disadvantages of vegetative propagation
(i) Advantages of vegetative propagation
-Plants that are propagated vegetatively are exactly like their parents they are true to type
- Plants established by vegetative means usually grow faster, and mature earlier than those established from seed
-Seed dormancy problems are completely eliminated in vegetative propagation
-Plants that do not produce viable seeds or do not produce seeds at all are only propagated through vegetative means
-Pollination agents which can fail to perform successfully are not required
- Failure of fertilization is avoided
-By budding and grafting, it is easy to achieve a number of desired objectives such as disease control, plant height, two varieties of the same crop on the same stock, etc.
-Vegetative propagation provides means for repairing damage to trees
Disadvantages of vegetative propagation
-The processes involved are time consuming
-There is possibility of the transmission of diseases in vegetative materials
-The planting material is usually bulky
-Vegetative planting materials cannot be stored for very long periods
-In vegetative propagation, all the plants on the field have the same characteristics/ No genetic variability
-Artificial vegetative propagation methods such as budding, grafting and layering require expertise
(b) Cultural methods used for controlling crop pests in the field
- Crop rotation
- Removal of pest infested plants / rouging
-Removal of debris which may harbour pests at different growth stages of the crop (sanitation)
-Use clean ,planting materials
-Seed dressing
-Use of catch crops
-Alteration of planting date /time to enable crops mature when build up of pest had not reached its peak
-Tillage practices such as hoeing to expose pests
-Use of pest tolerant varieties
-Weeding
(c) Harmful effects of chemical pest control
-Residues on edible produce pose health hazards to humans and animals
-There may be spraying injury to the crop due to an over concentration of the chemical
-The frequent spraying of some pesticides may result in the development of pest resistance
-It disturbs the biological or ecological equilibrium
- Causes air pollution
-Causes water pollution
-Causes soil pollution
-Decreases soil fertility by lowering soil pH