1. Will climate change result in more pest
and disease problems for agriculture?
Ray Cannon
Fera
Sand Hutton
York,UK

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

3. 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

4. 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)

5. 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

6. 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

9. 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?

10. 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

11. Free-Air CO2
Enrichment experiments - enrich the
atmosphere around part of a terrestrial ecosystem
with controlled amounts of CO2

12. 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!

13. 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

14. Reponses to
temperature
•Increases in:
o insect pest burden
oimpacts 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

15. 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

16. 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-1
earlier (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)

17. 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

18. 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

19. 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?

20. 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

21. 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

22. 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

23. 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”

24. 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)

25. Cameraria ohridella
Natural spread and
passive transport
Horse
chestnut
leaf miner

26. 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

27. 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

28. Citrus longhorn beetle –
Anoplophora chinensis

29. Damage caused by A. chinensis

30. Difficult to
detect!
Adult Citrus
longhorn beetle
on a feeding
tunnel in a thin
stemmed host
(Acer) with exit
hole

31. WHERE DOES IT COME FROM?

32. 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

34. Southern green shield bug
Nezara 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

35. 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

36. 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

37. Western corn rootworm –
a maize pest

39. 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)

40. White peach scale
Pseudaulacaspis 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

41. 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

42. Colorado Beetle Life Cycle

43. Leptinotarsa decemlineata
ecoclimatic indices predicted by
CLIMEX for 1961-1990

44. Leptinotarsa decemlineata
ecoclimatic indices (EI) predicted
for 2050 by CLIMEX under the
HadCM2 climate change scenario.

45. 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

46. 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

47. 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?

48. END OF TALK

49. 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!

50. Opportunities and risks
based 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

51. 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.

52. Adaptation solutions
• Improved pest management strategies
– To cope with increased climatic variability
• Changes in agronomic practices
– Earlier planting dates
– New, improved varieties and cultivars