Will climate change result in more pest and disease problems for agriculture?

Ray Cannon Fera

Sand HuttonYork,UK

INTRODUCTION

• Main ‘drivers’ of a changing climate• Direct and indirect effects• Effects of CO2 on crops and pests

Main ‘drivers’ of a changing climate

• An increase in atmospheric CO2 (and other greenhouse gases)

• Producing increased temperatures (T°C)• Coupled with altered precipitation ()

Producing biological effects such as:• Phenological changes (early flowering)• Geographical range shifts• Man’s responses: crop and land-use changes

Direct effects of climate change

• Longer (i.e. extended) growing seasons and frost-free periods

• Warmer, milder winters • Increase in the frequency & intensity of precipitation,

including:– Increase in ‘agriculturally significant’ extreme events

(e.g. floods; storms). – wetter autumn/winter period– lower rainfall in summer– Shifting regional rainfall (wetter in NW; drier in SE)

• Increased summer temperatures (Hotter & Drier)

Indirect effects of climate change

• Reduced water availability– Summer droughts: reduced water supplies for

agriculture and horticulture• Increased runoff, flash floods (extreme events)

– Disease management problems?

• Effects of increased CO2

– Changes in biomass & biochemistry of plants

– Yield gains (C3 crops) and losses

• Changes in type and variety of crops grown in UK

CO2 levels

– CO2 varied between 180 to 300 ppm for 400,000 years

– In phase with ice ages– Preindustrial levels were about 280 ppm– Current level is 385 ppm and rising by about 2

ppm per year– May reach 570 ppm by 2050?

• A doubling of CO2 probably results in a temperature increase of ~3°C

Responses to elevated CO2

High Uncertainty

The CO2 ‘fertilisation effect’: crops grown under elevated CO2 exhibit enhanced growth and yields

– C3 plants (crops, grasses, trees, shrubs) are particularly responsive

– C4 crops (maize, sugarcane, sorghum) are less sensitive

– Changes occur: in chemical composition (C:N ratios), plant defences, biomass, leaf area, canopy structure, abundance and distribution

– Big increase in fixation of C into organic matter (I.e. plant growth) but will it be sustained?

Plant defenses decrease (↓) as CO2 levels increase

Soybeans grown at elevated CO2 levels attract more pests - than plants grown at current CO2 levels

Experiments at high CO2 levels

Photo by E Deluccia

Free-Air CO2 Enrichment experiments - enrich the

atmosphere around part of a terrestrial ecosystem with controlled amounts of CO2

Pest and disease responses

• Given a choice, many insect species prefer feeding on foliage grown under elevated CO2

sugar levels but nitrogen (14%) and lack of chemical defences

• Insects lived longer and laid more eggs, but

• Large-scale, Free Air CO2 enrichment (FACE)

studies indicate decline in herbivory!

• CO2-temperature interactions and trophic level effects make predictions difficult!

Changes in precipitation

• Flooded soil – harvesting problems• Heavy rain – damage and bacterial infections

(rots)• Warm and wet winters – fungal infections• Long dry periods in

– Spring – can result in crop failure– Summer – growth and yield reductions

Reponses to temperature•Increases in:o insect pest burdenoimpacts on vegetation may oBackground levels of feeding may oNumber of pest outbreaks may oInsecticide usage may have to increase

Aphids may become more serious pests

Phenological changes (1)• Vegetated areas in Europe already show increase

in the length of the growing season– Most plants (including crops) are flowering

earlier• Spring bud burst & flowering dates of temperate

deciduous trees are in parallel with global warming – Many insects are flying both earlier and later

in the season, but – Dates of bud burst may not shift as much as

insect emergence - asynchrony

Phenological changes (2)

• Range of studies confirm change in timing of events • ‘First leaf onset’: 2.2 days decade-1 earlier (1955–2002 )• Spring/summer events: 2.5 days decade-1earlier (1971-2000)• ‘Spring events’: 2.3-2.8 days earlier per decade• Spring phenology (e.g. breeding, flowering or flying) was

5.1 days earlier• Butterflies: emerge much earlier and in advance of first

flowering dates (=asynchrony)

Range shifts

Tree species are expected to shift northwards as a result of climate change

Trees responded relatively rapidly to climate warming in the past

Climate warming will reduce growth and survival of some species, e.g. Scots pines

Crop and land-uses

• Effects of climate change will vary with crop type and region

• Crop yields may increase in some areas depending on availability of irrigation water & nitrogen

• But there may be effects on nutritional value – e.g. Lower protein content

• Unknowns include – extreme events; – pests & diseases

More on yields

• Elevated CO2 enhances crop yields of C3 crops (stimulates photosynthesis) but may be limited by Nitrogen availability

• C4 crops (maize, sorghum, millet) only benefit during drought stress– By 2020 global demand for maize

projected to exceed that for wheat and rice– MAIZE: the world’s most important crop?

Adaptation measures

• Farmers can decrease their vulnerability to climate change by:– Shifting planting dates – Growing alternative crops– Planting drought and heat-resistant

varieties– Selecting crops which respond well to

elevated temperatures and CO2

Adaptation measures are activities that enable ecosystems to adjust to climate change

Mitigation measures

Reduce level of CO2 or rate of increase by:

• reducing emissions (at the ‘source’) • increasing photosynthetic biomass (the ‘sink’)

i.e. Produce less GHGs and/or capture more

Mitigation measures (1)

• Reducing Green house gas (GHG) emissions from farming* (‘source’)• E.g. Reduced or less intensive tillage • Reduced fallow periods in summer• Reduced crop burning (non-UK)• Precision farming• Incorporating crop residues• Rotations of forage crops

N.B. Agricultural production accounts for 10-12% of all Man’s GHG emissions

Mitigation measures (2)

• Increasing photosynthetic biomass (‘sink’) – afforestation and reforestation – new large-scale plantations– rehabilitation of degraded land– more trees in agricultural areas– Increased yields via improvements in crops

“a resilient food system is one which can withstand, or recover quickly from, sudden shocks”

Factors driving the spread of pests

New species are arriving as a result of both Man’s influence and climate change:

• Natural expansion into unfilled ranges• Climate change driven shifts in ranges• Active dissemination on vehicles• Passive transport on traded plants and plant

products• Active flight (migrant species)

Cameraria ohridella

Natural spread and passive transport

Horse chestnut leaf miner

Horse chestnut leaf miner Cameraria ohridella

First seen in northern Greece in the late 1970's

Appeared in Austria in 1989 and has since spread throughout central and eastern Europe.

Arrived in the UK in 2002 and has rapidly spread northwards

Plant health pests

• Scale insects• Western corn rootworm• Citrus longhorn beetle• European corn borer• Southern Green Shield Bug• Colorado beetle• Old World bollworm • Phoma stem canker

Citrus longhorn beetle – Anoplophora chinensis

Damage caused by A. chinensis

Difficult to detect!

Adult Citrus longhorn beetle on a feeding tunnel in a thin stemmed host (Acer) with exit hole

WHERE DOES IT COME FROM?

Any increase in average temperatures will increase the potential for establishment and decrease the time required to complete it’s life cycle in the UK

Southern green shield bugNezara viridula

• Highly polyphagous• >100 crops• serious pest of food and

fibre crops• legumes, such as beans

and soybeans• Spreading northwards• 2003, three breeding

colonies in SE England

European corn borer (1)

•Pest of maize•Northward expansion in Europe•One or two generations•Possible occurrence of 2nd generation in areas where there is presently only one•Increased pest pressure

Ostrinia nubilalis

European corn borer (2) • Gradually

extending its range

northward through Europe

• Regular migrant to UK

• Breeding colonies mugwort

• 2010: damage seen for first time in maize crops in south-west England

Western corn rootworm –a maize pest

Western corn rootworm- UK is at the edge of its range,

- Could complete life cycle in most years.

- Considerable annual variation.

- By 2050 the average will be like a very hot year (1995).

Climate Change(2050)

Degree days available for development in different years

Cool(1996)

Hot(1995)

White peach scalePseudaulacaspis pentagona •Pest of deciduous fruit and nut trees (peach, walnut) and vines•Infestations cause dieback of twigs and branches and eventually death of the trees•Established outdoors for the 1st time in 2006, in Kent

Plant pathogens & Diseases – blackleg*

• Increased soil moisture, changes in the pattern of precipitation, elevated night-time temperatures and milder winters could all favour plant pathogens– increase the range and severity of phoma

stem canker winter oilseed rape predicted (Evans, 2008)

“The effects of climate change may be on the pathogen, the host or the host–pathogen interaction” *Leptosphaeria

maculans

Colorado Beetle Life Cycle

Leptinotarsa decemlineataecoclimatic indices predicted by

CLIMEX for 1961-1990

Leptinotarsa decemlineataecoclimatic indices (EI) predicted

for 2050 by CLIMEX under the HadCM2 climate change scenario.

Effect of Climate Change for the Colorado Beetle

• Potential range expansion of 120%

– 79 additional 0.5º latitude/longitude grid cells climatically suitable for colonisation

• Average northerly increase of 3.5° latitude (= 400 km)

• In total, 99.4% of the area of potato production in GB would be vulnerable

Climate change and weeds – upsetting the balance with crops• Any direct or indirect effect of climate change that

differentially effects the growth and fitness of weeds, relative to crops, will alter weed-crop interactions –sometimes to the detriment of the crop, sometimes to it benefit*– Many of the ‘worst’ weeds are C4 plants (which

may benefit from temperature and low dryness)– Most crops are C3 plants (which may benefit from

in CO2)

*D T Patterson (1995) Weeds in a Changing Climate

Implications of climate change for pest, weed and disease management

• More pests and diseases but possibly off-set by increased yields?

• New crops with new niches for invasive pests and diseases

• Increased pesticide use and possible loss of function?

END OF TALK

Robust and resilient farming systems (What & How?)

• “Integrated, biologically balanced crop management systems”

• “enhance the inherent adaptability of the system”

• “maintain resilience and buffer climate change”

• What can we do to build resilience? • Discuss!

Opportunities and risksbased on Defra’s Climate Change Plan*

• Hotter, drier summers and warmer, wetter winters– Opportunity to grow new crops (e.g. olives and

apricots) or existing crops further north (e.g. vines)– Some increased yields and less frost;

• BUT– Increased losses to pests and diseases– reduced quality and yield of some current crops.

http://www.defra.gov.uk/environment/climate/documents/climate-change-plan-2010.pdf

Opportunities and risks from climate change (2)

• Drought– Loss of pastures– Lack of water – Reduced crop yields

• Increased incidence of extreme weather events– Increased soil erosion– Storm and flood damage.

Adaptation solutions

• Improved pest management strategies– To cope with increased climatic variability

• Changes in agronomic practices– Earlier planting dates– New, improved varieties and cultivars