Environment and disease development on plants


Within the ecosystem, the condition of air, water

and soil, to a large extent determines whether

plant diseases would be epidemic or epidphytotic

1.e a condition when the number of individual plant


a disease affects can increase dramatically.


1. TEMPERATURE: Each pathogen has an optimal temperature for

growth e.g production of

spores (reproduction unit).

Temperature n this case affects the germination of mycelium.

Storage temperatures for certain fruits, vegetables,and nursery stock are manipulated to control fungi and bacteria that cause storage decay,

provided the temperature does not change

the quality of the farm products.


2. RELATIVE HUMIDITY: This is very critical in


fungal spore germination and the

development of storage and transit rots.

Rhizopus soft rot sweet potato (Rhizopus

stolonifer), is an example of a storage

disease that does not develop if relative

humidity is maintained at 85-90% High

humidity favors development of the leaf and

fruit diseases caused by fungi and bacteria.

Moisture is generally needed for fungal spore

germination, the multiplication

penetration of bacteria and initiation of


SOIL MOISTURE: High soil moisture levels

favour development water mold fungi such as

species of aphanomyces, pythuim,

Phytophtora. Excessive watering or over

watering decreases oxygen and raises

carbondioxide levels in the soil, making roots

more susceptible to root rotting organisms.

4. SOIL PH: The level of acidity or allkalinity


influences a few diseases such as common

scab of tomatoes and club root or crucifers

(plasmodiophora brassicae). Acidic soil wouid

encourage it. Addition of sulphur to soil can


help keep the soil at pH of about 5.0


5. SOIL TYPE: Some pathogens are favored by

loam soil and others by clay soils. Example is

phymatotorichum root rot which is serious

only in black alkaline sol- pH of 7.3 or above


that is low in organic matter.


6. SOIL FERTILITY: Lowering the level of

certain nutrient required by plants frequently influences the development of some infectious disease.

Some infection diseases

e.g. powdery mildew of what is destructive

after application of excessive amount of

nitrogen fertilizer. This condition can often

COunteracted by adding adequateq amounts of potash, fertilizer containing potassium.

Requirements for disease development


Proper environment: the most important

environment facts being the amount and frequently of rain of heavy dews, the relative

humidity and the air and soil temperature.


2. The presence of virulent pathogen.


3. A susceptible host.



Harvesting, storage and transporting food crops to

the final destination face tremendous challenges.

Damages to crops during harvesting or disease

units on them including environmental conditions

are the parameters that make up these challenges.

AS a result, farmers, marketers and. consumers

experience losses and poor products. If produce is

to be stored, it is important to begin with a high

quality product. The lot of produce must not

contain damaged or disease units and containers

must be well ventilated and string enough to with

and stacking.


Temperature control

Relative humidity

Air circulation

Maintenance space between container

Avoiding incompatible product mixes

It is important to note that commodities stored together should be capable of tolerating the same relative humidity temperatureander of ethylene in the storage facility or environment.

High ethylene producers such as ripe bananas,apples can stimulate physiological changes in ethylene sensitive commodities such as lettuce,cucumbers, and carrots, potatoes to often undesirable color, flavor and texture changes.

Updated: July 27, 2020 — 2:24 am

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