impact of climate change on agricultural pest and diseases interactions

1. Effect of climate change on crop pest interactions,
area shift, food production and supply
BY
MEDIDA SUNIL KUMAR

2. Main drivers:
Higher temperature may be more favourable for the proliferation of
insect pests (longer growing seasons, higher possibility to survive during
winter time)
Enhanced CO2 may affect insect pests through amount and quality of the
host biomass (higher consumption rate of insect herbivores due to
reduced leaf N)
Altered wind patterns may change the spread of both wind-borne pests
and of bacteria and fungi
Increased/decreased frequency of precipitation

3. Effect on plant diseases

4. Host pathogen and environment interactions

5. Effects on host and pathogens
• Changes in plant architecture may affect microclimate and thus risk infection
• Increased plant density-increased leaf surface wetness duration- more foliar
pathogen infection
• Increased frequency of heat and drought may contribute to disease
susceptibility/resistance
• Elevated CO2 levels - change plant structure- increased leaf area, increased leaf
thickness, more number of leaves, higher total leaf area, higher plant biomass-all
these would influence infection by pathogens
• Elevated O3 can change the leaf surface structure- affecting physical
topography and chemical composition, structure of epicuticular wax- may
influence pathogen infection- likely enhanced infection by necrotrophic
pathogens and root-rot fungi
5

6. • Plant pathogens are generally highly adaptable and likely to
exploit any compromise in plant defence caused directly or
indirectly by climate change.
• Higher temperatures may have an important repercussion on the
effectiveness of resistance genes and also elevated CO2 and ozone
levels could have an influence on the effectiveness of host
resistance.
• Climate change could firstly affect disease directly by either
decreasing or increasing the encounter rate between pathogen
and host by changing rates of the two specie.
• Some pathogens such as apple scab, late blight, and several
vegetable root pathogens are more likely to infect plants with
increased moisture .
• High CO2 concentrations may result in denser canopies with
higher humidity that favor pathogens.

7. • Increased CO2 can result in physiological changes to the host plant
that can increase host resistance to pathogens (Coakley et al 1999).
• Increased winter temperatures will likely mean higher populations
of pathogens survive to initially infect plants
• Increased temperatures will likely result in northward expansion of
the range of some diseases because of earlier appearance and more
generations of pathogens per season.
• Fungicide and bactericide efficacy may change with increased
CO2,moisture, and temperature.
• Systemic fungicides could be affected negatively by physiological
changes that slow uptake rates, such as smaller stomatal opening or
thicker epicuticular waxes in crop plants grown under higher
temperatures.

8. Effect on habitat:
 Plants and animals attempt to survive by shifting their
geographical ranges, as they have in past episodes of climate
change, they'll be blocked by farms and cities.
 "If half the world is driven to change its vegetation cover, and
meanwhile, we've fragmented the surface of the Earth by putting in
parking lots and monoculture agricultural zones and all these other
impediments to natural migration, then there could be problems.

10. High Precipitation Vs diseases
• Fungal pathogens are favored by high humidity.
• Aras will have high precipitation are more prone
to diseases and their incidence would be increased
by climate change

11. Vector born diseases
• Climate change may affect both host plant and insect-vector
populations, thereby affecting the spread of plant
viruses.
• Winter kill of vectors is low due to high winter
temperatures.

12. Eur J Plant Pathol (2012) 133:315–331

13. Eur J Plant Pathol (2012) 133:315–331

14. Effects on Plant disease management
 Delayed/adjusting planting dates less effective
 Increased vulnerability to biocontrol agents
 Reduced efficacy of chemical control
 Risk of movement of invasive pathogen species
 Reduced effectiveness of durable resistance
 Uncertainty for management method decision making
 Changing disease management strategy

15. Effects on ecosystem
Pathogen characterization might shift with climate change
• Pathogen effect on host survival, physiology and reproduction
• Life stages of host vulnerable to a pathogen
• Proportion of individual/biomass infected at a site
• Spatial distribution of infection
• Rate of pathogen effects on host in relation to response and
recovery
• Functional similarity of infected individuals versus replacements
• Frequency and duration of pathogen impact

16. Conclusions…..
• CC first affects the disease by increasing /decreasing the
encounter rates between host and pathogens by changing the
ranges of the two species
• Disease severity-positively correlated with increased virulence
and aggressiveness of pathogens which are mediated by host
resistance that is affected by climate change
• CC will affect plant diseases in relation to other global change
phenomena- new species, new vectors, shifts in land use,
expansion of tropical/temperate areas, loss of biodiversity etc.

17. Increased focus needed on:
 How a changing environment affects host-pathogen evolution
 Pathogen characteristics, such as frequency of generation and
proportion of sexual reproduction affect the rate of adaptation
 Host characteristics, such as life span affects rates of adaptation
of both host and pathogen populations
 Are invasive plant species better able to adapt to CC and move to
new areas rapidly?
 Are new invasive plant pathogens and vectors able to adapt
quickly?
 Local, regional and international cooperation and collaboration
needed to understand the problem and find solutions

18. Insects

19. Insects
• Insects are cold-blooded organisms
• Temperature is probably the single most important
environmental factor influencing insect behavior,
distribution, development, survival, and reproduction.

20. Changes in precipitation
• Insects are sensitive to precipitation and are killed or removed
from crops by heavy rains Ex: white fly, thrips.
• Aphids are not tolerant of drought their population may increase.
(Macvean and Dixon 2001).

21. Increased temperature
2oC temperature increase might experience one to five additional
life cycles per season (Yamamura & Kiritani 1998)
Warmer temperatures in temperate climates will result in more
types and higher populations of insects migratory insects may
arrive than earlier.
Temperature may change gender ratios of some pest species such as
thrips (Lewis 1997) potentially affecting reproduction rates.
Lower winter mortality of insects due to warmer winter
temperatures (Harrington et al., 2001)
Rising temperatures could result in more insect species attacking
more hosts in temperate climates (Bale et al 2002)
At higher temperatures, aphids have been shown to be less
responsive to the aphid alarm pheromone they release when under
attack by insect predators and parasitoids

22. • Baker, et al. (1998) estimated that for an average warming of
2.3°C, the Colorado beetle, Leptinotarsa decemlineata, could
expand its potential range in the UK by 120%.
• This would extend the potential northern limit of the species by 400
km, thus posing a potential risk to more than 99% of potato
producing areas.
• The northern extremity of its range, Diamondback moth, Plutella
xylostella generally occurs at relatively low population densities
and it does not usually overwinter.
• If however, as a result of global warming, overwintering
occurred more frequently, the pest status of this species would
increase dramatically (Dosdall 1994).

25. Elevated CO2
• Soybeans grown in elevated CO2 atmosphere had 57% more
damage from insects under FACE (free air gas concentration
enrichment)
• Insects sometimes feed more on leaves that have a lowered
nitrogen content in order to obtain sufficient nitrogen for their
metabolism
• Increased C: N ratios in plant tissue may slow insect development
and increase the length of life stages vulnerable to attack by
parasitoids (Coviella and Trumble. 1999).

27. Insects Have Some Control
Insects can significantly moderate the effects of temperature shifts
• Thermoregulation
• Activity Periods
• Digestive Control in Response to Food
• Quality
• Small environmental changes may have no real functional effect

28. Temperature & Food Quality
Interactions
• Nitrogen generally more important than carbohydrates to
performance
• C:N ratios affected by N-availability and C- accumulation
• Water
• CO2
• Nitrates
• Temperature
• Finite gut volume
• Digestion rate is temperature dependent

29. Possible control strategies
• Increased insecticides use new pest/disease
complex may probably emerge