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