fabioclass

DISEASE DEVELOPMENT AND TRANSMISSION


7.4 Stages of Diseases Development and Transmission
There are four major stages of disease development and transmission in crops.
These are:



1. Invasion: This is the stage where 'the disease causing agent comes in contact with the host plant.
2. Establishment
At this stage the disease causing agent enters and establishes llfe in the crop tissues.
3. Injury
This is the stage where the disease pathogen multiplies itself leading to the actual attack of the host.
4. Mission/Spread
This is the stage where the disease organism spreads from one plant to a healthy one. The process is aided by wind, water, insects contact and others.




7.5 Prevention and Control of Crop Diseases
It is better and more economical to prevent a disease from, crops than to control it when it has occurred. The sure way luting diseases, in farms is to prevent the disease causing organism from reaching the crops. This is possible through regular removal of rotten materials from the farm, routine spraying of crops planting resistant varieties and so on.

However, crop diseases can be controlled in the following ways:

1. Cultural Control
The techniques adopted in this control measure include:
(i) Proper care for plants such as regular weeding. This practice reduces the amount of disease attack on the crops.
(ii) Bunting, of farmland: This involves setting farmland on fire before cultivation. The fire helps to kill disease causing agent such as bacteria, fungi, virus and others in the soil.
(iii) Karly Planting: Early planting enables the crops to escape the outbreak of some crop diseases.
(iv) Practicing Crop Rotation: This practice, ensures that crop which suffer from similar diseases do not follow each other in the same rotation. This is to make sure that the cycle of the disease development is disturbed.
(v) Removal of dead plants and other disease harbouring agents from the farm. The source of the disease is removed when this is done.





2. Biological Control
This involves the use of good ar.cl resistant crops varieties to plant. It is a very successful method of controlling most seriou^ plant diseases. Over the years, scientists have developed crop types which have great resistance to some deadly crop diseases. The use of which helps to control most diseases of crops.

3. Chemical Control
This involves the use of chemicals to kill the disease organism affecting the crops. For example: (i) Fungicides such as perenox. Bordeaux mixture, and copper sulphate are used in the
control of fungus diseases.
(ii) Virus diseases can be controlled by using appropriate chemicals such as vetox 85 to kill the vectors e.g. aphids. mealy-bugs white flies, etc. that transmit the virus diseases.
(iii) Most bacterial diseases can now be treated using appropriatle chemicals (bacteriacides) such as Agrosan 5W mercurial duss and acid.
(iv) Nematodes can be controlled by using nematicides such a nemagoiu and DDT.

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You can read some of most interesting topics below
Agricultural biology topics


HERE YOU WILL FIND EVERY AVAILABLE TOPICS ABOUT AGRICULTURAL SCIENCE AND BIOLOGY. AND THE LINKS TO THEIR VARIOUS SOURCES.
1. DEVELOPMENT OF AGRICULTURE
2. IMPORTANCE OF AGRICULTURE
3. SUBSISTENCE AGRICULTURE
4. COMMERCIAL AGRICULTURE
5. PROBLEM OF AGRICULTURAL DEVELOPMENT
6. SOLUTIONS TO POOR AGRICULTURAL DEVELOPMENT
7. AGRICULTURAL LAWS AND REFORMS
8. ROLES OF GOVERNMENT IN AGRICULTURAL DEVELOPMENT
9. AGRICULTURAL POLICIES
10. PROGRAM PLANNING IN AGRICULTURE
34.
FORESTRY
35. WILDLIFE CONSERVATION
36. FACTORS AFFECTING LAND AVAILABILITY
37. TOPOGRAPHY
38. SOIL
39. BIOLOGICAL FACTORS
40. SOCIAL-ECONOMIC FACTORS
41. ENVIRONMENTAL FACTORS AFFECTING AGRICULTURAL PRODUCTION
42. CLIMATIC FACTORS AFFECTING AGRICULTURAL PRODUCTION
43. TEMPERATURE
44. RAINFALL
45. WIND
46. SUNLIGHT
47. SOLAR RADIATION
48. BIOTIC FACTOR AND AGRICULTURAL PRODUCTION
49. PESTS
50. BIRDS
51. DISEASES
52. SOIL MICRO-ORGANISMS
53. SOIL PH
54. ROCK FORMATION
55. IGNEOUS ROCK
56. SEDIMENTARY ROCKS
57. METAMORPHIC
58. SOIL AND ITS FORMATION
59. FACTORS OF SOIL FORMATION
60. LIVING ORGANISM
61. PARENT MATERIALS
62. SOIL FORMATION TOPOGRAPHY
63. PROCESS OF SOIL FORMATION
64. WEATHERING
65. PHYSICAL WEATHERING
66. CHEMICAL WEATHERING
67. PRESSURE
68. WATER
73. BIOLOGICAL WEATHERING
74. CHEMICAL AND BIOLOGICAL COMPOSITION OF THE SOIL
75. SOIL WATER
76. MICRO AND MACRO NUTRIENTS
77. SOIL MICRO ORGANISM
78. PROPERTIES OF SOIL
79. SOIL STRUCTURE
80. SANDY SOIL
81. CLAY SOIL
82. LOAMY SOIL

83. SOIL TEXTURE
84. IDENTIFICATION OF SOIL TYPES THROUGH EXPERIMENTS
85. RETENTION OF WATER BY VARIOUS SOIL TYPES
86. DETERMINATION OF SOIL PH REACTION
87. COLORIMETRIC DETERMINATION OF SOIL PH LEVEL
88. PH SOIL TEST
89. PLANT NUTRIENTS
90.
MACRO NUTRIENTS IN GENERAL
112.
THE MAINTENANCE OF SOIL FERTILITY
113. CROP ROTATION
114. APPLICATION OF ORGANIC MANURES
115. FARM YARD MANURE
116. APPLICATION OF INORGANIC MANURE

117. LIMING
118. FARMING PRACTICES
119. BUSH BURNING
120. CLEARING

121. FERTILIZER APPLICATION
122. ORGANIC MANURING
123. FARM YARD MANURE

124. HUMUS
125. COMPOST
126. CROP ROTATION
133. FARM POWER AND MACHINERY
134. SOURCES OF FARM POWER
135. HUMAN SOURCE
149.
PLOUGHS
142.
FIELD MACHINES
157.
PLANTERS
164.
SIMPLE FARM TOOLS
165. AGRICULTURAL MECHANIZATION
166. THE CONCEPT OF MECHANIZATION

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