Method of Weeds and Pest Control

Weeds

A Weed is any plant that grows in a place where it is not expected to grow or plant which grows out of place. A weed is a plant considered undesirable in a particular situation, “a plant in the wrong place”. Weed is any plant that grows in a place where it is not expected to grow or a plant which grow out of place. Such a plant constitutes nuisance either to man, livestock or plants.

Characteristics of weeds

1. Weed has the ability to regenerate itself – They are difficult to eradicate because of their regenerative feature
2. Weed produce many seeds which are easily dispersed
3. High resistant capacity – They are capable of withstanding very adverse weather conditions because of their tough protective seed coats
4. Weed has the ability to establish easy-grow faster than crop plants – weeds possess highly competitive and aggressive growth habit that can easily smother crops if not removed on time
5. Weed has ability to survive under adverse climatic and soil conditions – persistent
6. Weeds have devices for easy dispersal – These include spines, hooks, parachutes, wings with which they can be easily dispersed. Examples of weeds are – tridax, goat weed
7. Weed has long period of viability

Uses of weeds

1. They act as cover crop to control soil erosion e.g centrosema, calopogonium, stylosanthes
2. Weed can be used as much and compost materials. Much helps to conserve soil moisture while compost is an organic manure which improves soil fertility.
3. Weeds are used for food by man e.g. African spinach
4. Weed roots help to bind the soil particles to getting thereby preventing erosion.
5. They are sources of feeds to livestock e.g guinea grass, elephant grass, sedge
6. Some weeds are medicinal in nature e.g lemon grass
7. Weeds are major source of ornamental crops e.g pride of barbados, rose, canalily, hibiscus
8. Some weeds can control soil erosion.
9. Some weeds are used for roofing and mat making.
10. Weeds are used for compost making.
11. Leguminous weeds harbour bacteria that help fix atmospheric nitrogen in the soil

Effect/Economic Importance of Weeds

• Weeds compete with crops for sunlight – Weeds are capable of producing many large leaves which may grow and cover other plants around it.
• Weed compete with crops for nutrients – The roots of weeds develop rapidly and remove considerable amount of nutrients from the soil
• Weeds harbour crop pest and diseases – Some weeds may harbour crop pests and diseases
• Weed compete with crop for soil moisture – Their roots are capable of developing fast and removing large portion of moisture
• Losses in crop yield
• Weeds compete with crop for soil oxygen
• Some weeds act as parasites of crops and may kill their hosts e.g striga, dodder, mistletoe
• Losses in quality of crops
• Losses in income to farmers – The low yield coupled with the reduction in quality of produce affects the income of farmers.
• Some weeds are toxic to farm animal
• They increase the cost of production

Classification of weeds

1. Based on habitat (i) aquatic weed e.g water hyacinth (ii) terrestial weed e.g goat weed, tridax (iii) epiphytic (grow on other plants) e.g striga, dodder.
2. Based on life cycle (i) Annual (one year life span) goat weed (ii) Biennial weeds (2 years life span) e.g morning glory wild carrot.
3. Perennial (more than 2 year – life span) – elephant grass, sida acuta, spear grass.
4. Based on the type of leaves (i) broad leaf grasses

Methods of weed control

Physical (mechanical) method

1. Hoeing – use of hoe to remove the weeds from the roots
2. Hand pulling – hand is used to pull out the weeds
3.  Slashing – using cutlass to cut the shoot of weeds
4. Use of plough – uproot and bury the weed
5. Rogueing

Cultural method

1. Mulching – Mulch are spread on flat and to suppress weeds and prevent them from sprouting.
2. Flooding- water is led to the farm land to kill the weeds
3. Burning – the vegetation crop residue is set on fire to kill the weed seeds
4. Cover cropping – Fast growing legumes are planted to another weed
5. Crop rotation – It is effective for controlling weeds associated with specific crop – the weed starve to death.
6. Close spacing
7. Closed season

Biological Method- use of living organisms to control weeds

1. Use of parasites and predators to control weeds
2. Legume can be used to smoother weeds
3. Some animals like cattle, sheep can also feed on weeds
4. Insects can be used to kill some weed e.g cactoblastic is used to destroy cactus weed.

Chemical method

This involves the use of herbicides to destroy weed. Herbicides are chemical substances that can kill weeds.