2. Temperature
Humidity and
precipitation
Light
Wind
@ ML Murugan
3. Several research studies have indicated that
many crop plants may not be infected under
certain temp conditions.
It has been found in diff. rice varieties
Rice blast (night temp at 26c)
Temp variation ..though the cooling of leaves by
drops has not shown to have any effect on the
parasitic diseases.
@ ML Murugan
4. Various fungal disease are influenced by
temp,therefore,the development of disease stops
under extremely low and high temperature
conditions
@ ML Murugan
5. It is an important role in the incidence of pests and
diseases.
Soil moisture content has great influence on the
severity of soil borne diseases and the depth of
the existence of pest living in the soil.
Cooling of the leaves at night is caused by the
emission of infra-red radiation from the leaves.
Most parasitic fungi of foliage are believed
@ ML Murugan
6. To require free water for sore germination.
Some fungi can be germinate in h.humidity in the
absence of free water.
@ ML Murugan
7. Full day light reduces the germination or growth of
plant pathogens but many fungi germinate better
in light of moderate intensity than in complete
darkness.(powdery mildew)
On the other hand,the germination of certain rusts
may be much greater in darkness than in light.
@ ML Murugan
8. It has direct & indirect effect on the crop
plants.cold and hot winds can cause chilling and
sunburn,where as,strong winds can cause soil
erosion,high desiccation and mechanical injuries
to the plants.
Wind act as carrier of insects from place to place
and transport many diseases through the insects.
@ ML Murugan
9. It is the period in which infection has taken place
but symptoms do not occur.
Temperature influences the latent period.
It depends on:
nature of pathogen
type of host
environmental conditions
@ ML Murugan
10. It is the period from appearance of symptoms
to the release of spores. It is also influenced by
weather variables. Eg:infection period of peanut
rust is influenced by temperature.
@ ML Murugan
11. Climate conditions are favourable for the wheat
rust to servive in the himalayan region during
summer season on the host plant of
barberry.nepal(source region of rust-during
summer)
Nilgiri hills in south india are the source region of
wheat rust.
@ ML Murugan
12. Wheat rust appears in in north-west india when
there exist favourable weather conditions.
It can be divided into three types
@ ML Murugan
13. Due to low temperature(confined to northern parts
of India).the weather conditions become
favourable for the appearance of rust by the end
of January.
Air temperature between(9-13∘c)
R.humidity more than 70%
There must exist partly cloudy conditions.
@ ML Murugan
14. It can survive over a wide rage of temperature.
(northern&southern hills are the regions).it
appears in punjab during the month of february.
Air temp between 15-20°c
R.humidity should be more than 70%
Intermittent cloudiness must exist in the end of
january or 1st week of february.
@ ML Murugan
15. It can survive in the northen hills throughout the
summer season.(source is nilgiri hills)
End of february –mid march only it can appears.
Mean air temperature between 16-27°c
R.humidity should be 70%
There should be excessive dew
@ ML Murugan
16. During winter season, western disturbances cause
cloudiness,rains,dew and fog over north
india.when It become favourable ,late blight of
potato appears.
During summer season,incidense of late blight of
potato is common in hilly regions.
@ ML Murugan
17. The weather conditions which are favourable for
the incidence of many rice diseases.
@ ML Murugan
18. Min temp. should be less than 26°c
R.humidity should be more than 90%.
If these conditions prevail during the period of
seedling,tillering and ear emergence, then the disease is
likely to appear.
@ ML Murugan
19. Temp. range between 19-37°c in summer,
17-26°c in winter season.
High relative humidity should persist.
Irrigated conditions is more susceptible to this disease.
@ ML Murugan
20. There should be excessive rainfall during the
reproductive period.
High humidity & lower temperature should persist.
@ ML Murugan
21. Temperature should between 30.4-32.7°c
Relative humidity between 86-93 %
Sunshine hours should range between 3.3-7.8 hrs per
day
These conditions adversely affect the spread of the
disease.
@ ML Murugan
22. Leaf spot it is an important disease of groundnut.
It may be two types early leaf spot and late leaf
spot.
This disease is more common in those areas,
where groundnut cropping system is existing.
Early leaf spot - can appear few weeks of
sowing(damage 10-15%)
@ ML Murugan
23. Leaf wetness is also one of the causes of these
disease.(higher in kharif season)due to dew, fog
and rainfall
Favorable temp(22-35⁰c)
@ ML Murugan
24. It may appear at any phonological stage of the
crop. it is influenced by temperature conditions,
leaf wetness and high humidity.
Fav.conditions(temperature at 24c,r.humidity
87%,intermittent rain fall)
@ ML Murugan
25. Temperature around 20-25c
High and prolonged rainfall
Intermittent cloudiness & dew
Strong winds are favourable for disease spread
@ ML Murugan
26. It appears at flowering and podding stage in the
form of pycinia and aecia.it germinates at 17-22c
and infect other plants forming either
Secondary aecia or uredia depending upon
prevalent temperature of 25c
@ ML Murugan
27. It appers at the larger stage of the crop during
rainy season.intermittenet rains are favourable for
the disease development.
Tempv22.5-23.5c
R.humidity between 77-86%
Sunshine more than 5 hrs
Should me more no. of rainy days.
@ ML Murugan
28. temp at 20-25c
R.Humidity should be around 92% during rainy
seasons.
Cloudy weather.
@ ML Murugan
29. IPCC, 1996a. Climate Change 1995: The Science
of Climate Change.
@ ML Murugan
30. Kattenberg A., Maskell, K. (Eds.), Contribution of
Working Group
I to the Second Assessment Report of the
Intergovernmental Panel
on Climate Change. Cambridge University Press,
Cambridgeetc.
@ ML Murugan