Disease Organisms, Prevention And Control In Agriculture

.     Bacteria

2.     Fungi

3.     Virus

4.     Nematode

1.      Bacteria: These are micro-organisms which can not be seen with naked eye unless we use a powerful microscope. Bacteria are found every when even under a condition where other living organism cannot exist such as in water in soil in the air in plant in animal, etc

 

Bacteria: These  are useful to man in the following ways:

i.                    The help in the decomposition of compost  and organic materials.

ii.                  They are useful in the fermentation process e.g. production of drinks such as beer, wine, etc.

iii.                They are also useful in the making of cheese.

iv.                They also help to fix atmospheric nitrogen into the nodules of legumes..e.g Azotobacter, Nitrosomonas.

On the other hands, bacteria causes crop disease which are transmitted  from one plant to another by wind, rain splash and by insects.
Examples, of such disease include the following Bacteria Blight of Cotton, Bacteria Blight of Guinea Corn,

Bacteria Wilt of tomatoes.

 

2.      Fungi: These are also microscope organism and they are regarded as plant but they do not process chlorophyl root, stem and leaver. But they leave as parasite on plant and transmitted of disease or diseases e.g. maize, smut, leave rust or leave spot, black pour, of cocoa, damping off, can be transmitted by wind , rain splash , by insect, etc.

3.      Virus: These are microscopic  organism, smaller than Bacteria and Fungi.They can only be seen under very powerful microscopic or electronic microscopic. They cause serious and civil diseases in crop plant. Virus diseases are transmitted by piercing and sucking insects. Disease cause by viruses include Coca Swollen Shoot, Groundnut Rosette,  Cassava and Yam Mosaic, etc.

 

4.      Nematode: These are soil born organism. They are worm like animals. Many of them live on dead organic matter while others live as parasites on plants. Some are microscopic while others are  big enough to be seen with naked eye. The parasitic nematode  attack plant hosts and caused diseases such as  Tuber rot, Root knot, Die back, etc.

       

SIGNS AND SYMPTOMS OF CROP DISEASES

1.      Yellowing and wilting of plants leaves

2.      Curling, twisting and winkling of leaves.

3.      Stunted Growth.

4.      Rottening  of leaves, stems and roots.

5.      Defoliation of plants

6.      Brown patches  with spots showing dead areas on leaves.

7.      Mouldy grains.

8.      Death of Plants

9.      Reduced product quality.

1.  Low Yield.

 

EFFECTS OF DISEASES ON CROP

1.      Poor yield

2.      Low quality and loss of market value.

3.      Delayed maturity.

4.      Death of crops

Crop Diseases In Agriculture

DEFINITION OF A DISEASE

Disease can be define as a condition of ill-health in  an organism. Disease can also  be referred to as deviation from the normal physiological condition which results in the abnormal function of the body system either in part or as a whole.

A crop disease is a condition in which crop plants suffer from abnormal health condition.

CONDITIONS THAT NECESSITATE OCCURRENCE OF DISEASES IN  CROPS

The following conditions must be met before a disease can occur in crop plants.

1.      There must be a Pathogen/Disease causing organism.

2.      There must be a Susceptible Host.

3.      There must be a conducive environment.

DISEASE TRIANGLE

Pathogen

                              Crop Plant                                              Favourable Condition

               

                  

If any of the three conditions is absent, there cannot be a disease infection.

STAGES OF DISEASE DEVELOPMENT

The various stages of  development of diseases include:

i.                    Over-seasoning stage.

ii.                  Innoculation stage.

iii.                Penetration stage.

iv.                Infection stage.

v.                  Incubation stage.

vi.                Invasion stage.

vii.              Dissemination.

i.                    Over-seasoning stage: This is the resting period during which disease organism (pathogen) changes to a particular form to survive unfavourable environmental conditions. At this stage the pathogen is not active on until a conducive period is attained and it becomes active.

ii.                  Innoculation Stage: This is the stage at which the pathogens makes contact with the plant either by wind, water vector, etc .

iii.                Penetration Stage: This is the stage  at which the disease organism gains entrance into the cell of the host plant through leaves, cuts or other opening .

iv.                Infection Stage: This is the stages at which the pathogens causes damages to the cell of the host plant .

v.                  Incubation Stage: This is the stage between the period of contact and when symptoms begin to manifest. It is the stage at which the diseases is fully establish in the cell of the host plant and it shows changing in the appearance of the host plant indicating the presence of diseases.

vi.                Invasion Stage: At this stage the disease is fully established in the host plant multiplies rapidly and spread from one cell to the other in the host plant until it's tissues are complete damage.

vii.              Dissemination stage: This is the stage at which the disease continuous to spread from the host plant to the other plant by wind, water, vector.etc .

FOREST MANAGEMENT

A forest can be defined as a piece of land with thick or very thick vegetation. It can also be referred to as a large expanse of land covered with wild trees and bushes either growing wild or planted for some purposes.                         

 Forestry can also be defined as the management of forest land and their resources to provide economically useful goods and services. It involves the production, distribution and utilization of forest products and services.    

               Forest management can therefore be defined as conditions under which forest and its resources could be managed to avoid wastage and degeneration. 

Some of the terms associated with forestry include;-  

1.   Selective Exploration:  This can be defined as selective felling of trees based on maturity i.e trees must be inspected and be said to be matured before being cut down.    

2.   Taungya System: This is a system of farming whereby crops are planted along side with forest trees.

3.   Forest Regulation:  This is the law that guides felling of trees and the use of other forest resources.

4.   Regeneration: Regeneration is a situation whereby trees that are cut in the forest regenerates or grow again.

5.   Deforestation;- This is the act of felling trees indiscriminately.

6.   Afforestation: This is the planting of new trees to replace the ones that have been cut.

7.   Re-forestation:  Re-establishing a forest after the initial trees have been cut down.

ADVANTAGES OF FOREST

1.   It serves as game reserve.

2.   It serves as windbreak.

3.   It conserves soil moisture by preventing evaporation.

4.   It controls erosion.

5.   It prevents leaching.

6.    It serves as centre of tourist attraction.

7.   It helps in recycling of materials.

8.   It provides employment.

9.    It is a source of foreign exchange.

10.    It preserves wild life.

11.    It fertilizes the soil.

DISADVANTAGES OF DEFORESTATION

1.    Deforestation encourages soil erosion.

2.   It leads to loss of organic matter which eventually leads to loss of soil fertility.

3.   It leads to decrease in soil moisture retention.

4.   It increases leaching.

5.   Deforestation reduces the population of wildlife in the area that is concerned.

6.    It can lead to desertification.

7.   It reduces supply of forest products to the industry.

                   

USES OF FOREST AND FOREST PRODUCTS

   

1.   Provision of food for the people.

2.   Timbers from the forest are used by furniture and other industries.

3.   Fruits, vegetables animals are sourced /gotten from the forest.

4.   Raw materials from some of the forest plants are used in industries for the production of oil palm, rubber and fibre.

5.   Plant root, barks and leaves are rich sources of herbs and medicine.

6.   Plank generates revenue for government.

Write down 10 forest trees, Yoruba name, English and Botanical

	Forest trees	Yoruba name	English name	Botanical name
1	African Oak	Ekki	Oak	Lophina alata
2	Ebony	Igedu	Ebony	Diospyros tropurepure
3	Mahogany	Oganwo	Mahogany	Khaya seregac ensis
4	Teak		Teak	Clorophora exceisa
5	African peach	Egbesi	Peach	Sarexphalus esculeitus
6	Can wood	Irosun	Camwood	Baphla nidita
7	Sass wood	Erun	Sass wood	Erythrophieum guireense
8	Brimstone wood	Opepe	Brimstone	Terminaloa specie
9	Mangrove	Egba	Wood	Rhizopora racemasu
10	Shea butter tree	Emi-emi	mangroove	Burry ospermum parki