Climate change is altering plant disease development through its effects on the disease triangle of pathogens, hosts, and the environment. Rising CO2 levels can both increase pathogen growth and modify plant defenses. Higher temperatures can influence pathogen virulence and host resistance. Changes in precipitation patterns impact moisture levels and thus disease occurrence. Climate change is modifying the effectiveness of disease management approaches like fungicides. More research is still needed to fully understand and address the impacts of climate change on plant health.

1. Effect of Climate Change
on Plant Diseases
Name: INDRAJ BISHNOI
Roll No.: 2022-PPMGA-106
Class: M.Sc. (Ag.) Plant Pathology
En. No.: GN7210

2. Introduction
 The term “Disease” refers to any malfunctioning of host cell, resulted from continuous
irritation by a pathogenic agent or environmental factor and leads to development of
symptoms.
disease
Environment
Pathogen
Host
Favorable
Susceptible
Virulent
Disease Triangle
The diseases posing significant risks to global food security are the result of interaction
between susceptible host, virulent pathogen and favourable environmental conditions

3.  As a component, environment is quite crucial in disease development and any changes in
it can be strongly correlated with the changes in disease severity and losses due to it. As:
 The in-frequent late rainfall led to elevated Ascochyta blight incidence in chickpea
(Abang and Malhotra, 2008).
 El-Nino in Ethiopia altered the rainfall pattern which aggravated rust incidence and
total crop failure in late planted lentil during 1997-1998 (Varma and Winslow, 2004).
 The climate change further facilitating the emergence of new pathogenic strains.
 In context with plant diseases, CO2, Ozone and temperature are most responsible factor
for altering the host-pathogen interaction and their geographical distribution.

4. Climate change and the disease triangle

5. Epidemics occurred due to climate change
Plant Diseases Causal organism Location Climate Change Author
Downy
mildew in
grape vines
Plasmopara
viticola
Nort-west
Italy
Increase in temperatures and
precipitation
Salinari et
al., 2006
Swiss needle
cast
Phaeocryptopus
gaeumannii
Oregon
coasts
(USA)
Increase in temperature
during winter and duration
of leaf wetness during
spring and autumn.
Stone et al.,
2008
Alternaria
blotch of
apple
Alternaria mali
Kashmir,
India
Prolonged rains followed by
high temperatures.
Bhatt et al.,
2015

6. Causes of climate change
Natural Causes Anthropogenic Causes
1) Volcanoes
2) Intensity of solar radiation
1) Green houses Gases
Carbon dioxide (Co2)
Methane (CH4)
Nitrous oxide(NO2)
Chloro floro carbons (CFCs)
Ozone (O3)
Water Vapors (H2O)
2) Land Use Change
Deforestation
Urbanization

7. Effects of Climate Change
On Plant Disease development

8.  The atmospheric CO2 concentration has increased to over 400 parts per million and
continues to increase.
 An increase in CO2 levels may encourage the production of plant biomass, thus, can
modify the microclimate and affect the risk of infection (Lambers et al., 2008), as:
 Higher CO2 concentrations elevates rust incidence (Chakraborty et al., 2002), but
 Low concentration of carbohydrates may lead to plant stress and hence promote disease
development (caused by climate or fertilization).
 Elevated levels of CO2 has direct effect on the growth of pathogens, as in:
 Powdery mildew of barley both the disease incidence and the percentage of active
conidia are higher at elevated CO2.
 Fusarium graminearum incidence and severity, increases with rise in CO2 levels
 The increasing CO2 concentration may produce negative effect in the case of Peronospora
manshurica.
Effect of elevated CO2

9.  Dense canopy favors the incidence of Rust,
Powdery mildew, Alternaria blight,
Stemphylium blight and Anthracnose
diseases.
Diseases due to elevated CO2 concertation
Stem rust
Powdery mildew of field pea
Alternaria blight
Anthracnose

10. Case Study
Kobayashi et al. (2005)
 Rice plants grown in an elevated CO2
concentration were more susceptible to leaf blast
than those in ambient CO2 as indicated by the
increased number of leaf blast lesions.

11. Effect of ozone (O3)
 Not only CO2, but Ozone may also affect the host-pathogen interaction and disease
development.
 Elevated Ozone may increase disease severity in wheat infected by Drechslera spp.
Few more examples of impact of elevated ozone levels on disease development
S. No. Fungi Host Plants Effect on disease
1 Puccinia graminis f.
sp. tritici
Wheat Decreased hyphal growth and urediospores on
O3 injured leaves
2 Erysiphe graminis f.
sp. hordei
Barley Reduce rate of infection if exposed to
sufficient O3 during incubation
3 Botrytis cinerea Potato Infection only in injured leaves
4 Lophodermium sp. Pine Increased severity of needle blight
Manning and von Tiedemann, 1995

12. Stem rust of wheat Powdery mildew of barley
Grey mould of potato

13.  The changes in temperature and precipitation regimes may alter the development rate and
pathogenicity of infectious agents, and the physiology and resistance of the host plant
(Charkraborty and Datta, 2003).
Effect of Temperature
 Temperature is one of the most important factors affecting
the occurrence of bacterial diseases such as Ralstonia
solanacearum, Acidovorax avenae and Burkholderia
glumea.
 The incidence of vector-borne diseases and distribution of
vectors is greatly influenced by temperature.
 Aggressiveness in stripe rust (Puccinia striiformis)
increases in elevated temperature conditions (Mboup et al.,
2012)

14.  Inoculated Anthuriums plants exposed to temperature greater than 310C (87.80F) were
more susceptible to disease than inoculated plants exposed to 260C (78.80F) or lower
temperatures.
 Plants grown at 260C developed few symptoms following inoculation, while plants grown
at 310C showed severe blight.
Case Study

15. Effect of Rainfall
The occurrence of many diseases in a particular region is closely correlated with the amount
and distribution of rain fall within year.
Late blight of potato, apple scab, downy mildew of grapes and fire blight are found or are
severe only in areas with high rain fall or high relative humidity during the growing.
Fire blight of apple Downy mildew of grapes Apple scab

16. Moisture plays an important role in host-pathogen interaction, by acting as an important
factor for production, germination distribution and spread of propagules.
Increased incidence of diseases (as late blight and apple scab) have been reported with higher
moisture content, at the same time Low moisture favours powdery mildew disease.
The late blight of solanaceous plants (tomato and potato) occurs most frequently at high
moisture coupled with temperatures range of 7.2°C and 26.8°C.
The disease like dry root rot and powdery mildew in legumes may become serious under
increased dryness (Gautam et al., 2013).
The drought conditions also affect incidence and severity of some viruses (Clover et al.,
1999).
Effect of Moisture

17. Apple scab Late blight of potato
Dry root rot of chick pea Powdery mildew of soybean

18.  Increase in temperature can modify host physiology and resistance, due to decrease in
durability of resistance genes (due to the evolution of pathogen races) (Garrette, 2006).
 In brown rust of wheat, the host-pathogen gene pairs related to resistance responded
differently to different temperature ranges (Browder and Eversmeyer, 1986).
 Lignification of cell walls increased in forage species at high temperatures to enhance
resistance to fungal pathogens (Strange, 1993).
 The crops may harbour pathogens as symptomless carriers and disease may develop if
plants are stressed in a warmer climate.
 Drought has additive effect on disease stress, this has been reported in Xylella fastidiosa,
Beet yellows and Maize dwarf mosaic virus (McElrone et al., 2003).
Effect of climate change on host resistance

19. The efficiency of fungicides can get altered due to change in duration, onset and
intensity of precipitation.
Higher level of precipitations can lead to the wash-off of fungicides.
The temperature influences the degradation of pesticides and alters the morphology and
physiology of plants affecting their penetration, translocation and mode of action (Elad
and Pertot, 2014).
According to Ghini (2008) increased canopy due to elevated CO2 can affect the
penetration, translocation and mode of action of systemic fungicides.
As far as biological control is concerned less information is available. However studies
suggests that: increased CO2 concentration may lead to increase efficiency in VAM and
Trichoderma harzianum T39 (Elad et al., 1993).
Effect of climate change on disease management

20. Conclusion
 Climate change can have positive or negative effect on crops and their diseases.
 There has been however limited research on impact of climate change on plant diseases.
 Modified chemical and biological control need to be implemented against diseases in the
changing climate scenario.
 It is a responsibility of a breeder too to begin gene expression analysis towards various
biotic and abiotic stresses.
 Climate prediction models have been however also developed against plant diseases.
 Climate change is burning issue in today’s century. There is a need of collaboration of all
the disciplines together to mitigate this global problem. More rational approaches need to
be taken to know the actual mechanism of impact of climate change on plant diseases.
 Climate change may results positive, negative, or no impact on individual plant- patho
system.

21. Thank you