Effect of climate change on crop pest interactions, area shift, food production and supply
BYMEDIDA SUNIL KUMAR
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
Main drivers:
Effect on plant diseases
Host pathogen and environment interactions
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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
• 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.
• 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.
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.
Effect on habitat:
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
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.
Eur J Plant Pathol (2012) 133:315–331
Eur J Plant Pathol (2012) 133:315–331
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
Effects on ecosystemPathogen 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
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.
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
Insects
Insects
• Insects are cold-blooded organisms
• Temperature is probably the single most important
environmental factor influencing insect behavior,
distribution, development, survival, and reproduction.
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).
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
• 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).
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).
Insects Have Some ControlInsects 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
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
Possible control strategies
• Increased insecticides use new pest/disease
complex may probably emerge
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