Climate change will impact crop protection from weeds, pests, and pathogens. Global studies show weeds cause 34% of potential crop losses, pests cause 18% of losses, and pathogens cause 16% of losses. Changes in temperature and rainfall from climate change can influence these threats in several ways. Higher temperatures may increase weed and pest presence earlier in seasons and alter balances between pests and natural enemies. More variable rainfall could favor some weeds and pathogens but inhibit others. Changes in temperature and moisture conditions may also impact the spectrum of which pathogens affect crops and their severity. Effective adaptation will require acknowledging change is inherent and that current adaptive capacity must be maintained.

1. Climate change and crop
protection
David Nehl

2. CROP PROTECTION --- DAVID NEHL
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D P I Crop protection
Potential global losses (Oerke 2006)
– Weeds ~ 34%
– Pests ~ 18%
– Pathogens ~ 16%
Less in Australia
17% loss in winter crops in 1998-99 (Jones et al. 2005)

3. CROP PROTECTION --- DAVID NEHL
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Host Pathogen
Environment
Environment

4. CROP PROTECTION --- DAVID NEHL
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D P I Key factors
Temperature
Rainfall
Humidity

5. CROP PROTECTION --- DAVID NEHL
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D P I Climate change and crop protection
Impacts
–Weeds
–Pests
–Pathogens
Implications

6. N S W
D P I Climate change and crop protectionWeeds are opportunists
Short life cycles
High reproductive rates
Rapid response to rainfall events
Adapted to a wide range of environments & soils
CROP PROTECTION --- DAVID NEHL
Weeds

7. CROP PROTECTION --- DAVID NEHL
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D P I
Changes in frequency
‘Summer’ weeds likely to increase
Weeds adapted to variable rainfall favoured
Climate variability may alter herbivory
Climate change and weeds

8. CROP PROTECTION --- DAVID NEHL
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D P I Pests
Short life cyclesShort life cycles
HHigh reproductive ratesigh reproductive rates
Temperature dependentTemperature dependent

9. CROP PROTECTION --- DAVID NEHL
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D P I
Temperature increase
– Changes in frequency
– Shorter generation time
– Earlier pest presence
– Control windows may change
– Balance between pests and beneficials may alter
Rainfall intensification
– Over-wintering may change
Climate change and pests

10. CROP PROTECTION --- DAVID NEHL
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Rapid response from pathogens with:
– Short generation time
– High reproductive rates
– Effective dispersal
Response will be variable
Pathogens

11. CROP PROTECTION --- DAVID NEHL
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5
Temperature (°C)
Growth
of fungi
10 15 20 25 30
Temperature and plant pathogens

12. CROP PROTECTION --- DAVID NEHL
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D P I
13
Soil temperature (°C)
0
10
20
30
40
50
Cotton
seedling
mortality
(% death)
14 15 16 17 18
Temperature and disease

13. CROP PROTECTION --- DAVID NEHL
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D P I Black root rot of cotton

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October
© Australian Bureau
of Meteorology 2006
9-12°C
12-15°C
6-9°C
9-12°C
*
Cotton sown 10 Oct
Mean minimum air temperature 2003
One month after sowing
black root rot severity
= 7.6
(0-10 scale)

15. CROP PROTECTION --- DAVID NEHL
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D P I
November
15-18°C
18-21°C
12-15°C
15-18°C
*
Cotton sown 10 Nov
One month after sowing
black root rot severity
= 2.2
(0-10 scale)
Mean minimum air temperature 2003
© Australian Bureau
of Meteorology 2006

16. CROP PROTECTION --- DAVID NEHL
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D P I Rainfall and disease
Rain events
– Favour some pathogens

17. CROP PROTECTION --- DAVID NEHL
N S W
D P I Rainfall and disease
Rain events
– Favour some pathogens
– Inhibit others

18. CROP PROTECTION --- DAVID NEHL
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D P I Dew period

19. CROP PROTECTION --- DAVID NEHL
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D P I Rainfall and disease
Rain events
– Favour some pathogens
– Inhibit others
Rain events and temperature are linked

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D P I
12 Feb 2002

21. CROP PROTECTION --- DAVID NEHL
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D P I
1 Mar 2004

22. CROP PROTECTION --- DAVID NEHL
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Changes in spectrum of pathogens
Impacts on disease severity
– Positive
– Neutral
– Negative
Climate change and disease

23. CROP PROTECTION --- DAVID NEHL
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Cooperating growers
Acknowledgments

24. CROP PROTECTION --- DAVID NEHL
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Impacts
– Changes in pest/pathogen/weed spectrum
– Responses will be variable
Implications
– Change is inherent
– Adaptive capacity is currently present
Conclusions