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.
STORAGE, TRANSIT AND MARKET DISEASE OF FRUITS AND VEGETABLES
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
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.