Effect of Environmental Factors & Nutrition on Plant Disease Development.

Question 1

Environmental Factors Influences

Answer 1

1. Growth & susceptibility of host
2. Multiplication & activity of pathogen
3. Interaction between the host & pathogen

Question 2

Effect of Temperature

Answer 2

• Optimums for plant & pathogen
• Temperature also affects the incubation period/latent period,generation time,infectious period.

Question 3

example of virus pathogenicity by Effect of Temperature

Answer 3

Viruses producing Leaf-Roll symptoms are severe in summer

Viruses causing Mosaic or Ringspot symptoms are more pronounced in spring

Question 4

How moisture favours Pathogen

Answer 4

-Spore germination & germ tube penetration
-Activation of bacteria
-Increased succulence of plants
-Soil pathogens often more virulent when soil near saturation point

Question 5

How moisture favours Plant?

Answer 5

• Adequate water helps ensure healthier plant
• Turgidity results in cell elongation

Question 6

Effect of Wind

Answer 6

Causes of wounds
–Direct wind damage
–Wind-blown sand
–Plants rubbing

Dries plant surface

Releases spores & bacteria from infected tissue

Question 7

what Environmental Factors most involve in disease epidemics

Answer 7

pathogens which are spread directly by the wind or indirectly by insect vectors that can be carried along long distances by the wind.

Question 8

Effect of Light

Answer 8

Plants that do not receive required amount of light to meet their cultural requirements become stressed.

Low light usually favours susceptibility to viral infections.

Question 9

Effect of Soil pH

Answer 9

Usually affects pathogens more than plants

Question 10

pathogen example for Effect of Soil pH

Answer 10

Plasmodiophora brassicae (Clubroot) Optimum at pH 5.7, Inhibited at pH 7.8

–Streptomyces scabies (Potato Scab) Optimum pH 5.2 to 8.0, Inhibited below 5.2

Question 11

Nitrogen deficiency

Answer 11

causes weaker, slower growth, faster aging

Greater susceptibility to pathogens that attack weak, slow- growing plants

Question 12

pathogen that have higher susceptibility under Nitrogen deficiency

Answer 12

Fusarium (Wilt) on Tomato
Alternaria solani (Early Blight) in Solanaceae

Question 13

Phosphorus advantage

Answer 13

Increases, it either Improves nutrient balance in plant or accelerates maturity of crop.

Allows it to escape infection making it resistant towards the invading pathogen.

Improves tolerance to disease that can increase crop yield & quality.

Question 14

protection of Phosphorus Increases often related to

Answer 14

the role it plays in plant development

Question 15

what Phosphorus deficiency cause

Answer 15

Reduced growth

Question 16

Potassium advantage

Answer 16

Reduces severity of numerous diseases,eg: Stalk Rot of Corn

Promotes wound healing

Increases resistance to frost injury

Question 17

Excess Potassium lead to

Answer 17

severity of some diseases, eg: Rice Blast

Question 18

Calcium function

Answer 18

is an essential part of plant cell wall. It forms calcium pectate compounds which gives stability to cell walls and bind cells together,therefore strenghtens the cell wall structure.

Stronger Cell walls, induced by calcium, can avoid the invasion.

Question 19

what are the common calcium sources for plants

Answer 19

calcium nitrate, calcium chloride, and lime