Download Blackleg Disease Management – Cultural Controls

Blackleg Disease Management –
Cultural Controls
Ralph Lange
Alberta Innovates – Technology Futures
Is there a place for cultural control
methods?
Disease contingent on Host/Pathogen/Environment
triangle
Long-lasting control requires integrated approach
Cultural control can disrupt disease cycle
Integrated approach can slow breakdown of genetic
resistance
Forms of cultural control
applicable to blackleg:
Crop rotation
Sanitation
Tillage
Burning
Disease-free seed/seed
treatment
Crop rotation decreases blackleg
severity
Severity (0-5)
3.5
3
% incidence
2.5
2
Clear reduction in
severity due to oneor two-year break
with wheat or wheatfallow (Carman, MB Guo et
al.2005)
1.5
1
0.5
0
CCCC
CWCC CCWC CWFC
Crop rotation decreases blackleg
severity
3.5
Severity (0
(0-5)
3
2.5
2
1.5
1
0.5
0
1
2
3
Crops/4 years
Westar
Quantum
Lange & Kharbanda, 2002, Viking, AB
4
Crop rotation decreases blackleg
incidence
100
% Incidence
80
60
40
20
0
1
2
3
Crops/4 years
Westar
Quantum
Lange & Kharbanda, 2002, Viking, AB
4
Canola Cropping Frequency Black DG East soil zone
Based on AFSC data
500
canola on canola
1 year break
2 year
3 year
4+
on fallow
450
400
350
Records
300
250
200
150
100
50
0
2004
2005
2006
2007
2008
2009
Tillage in western Canada
Conventional
AB
Conservation
No-till
SK
MB
0
10
20
Seeded ha (‘000,000)
Statistics Canada, 2007, Selected Historical Data from the Census of Agriculture: Table 5.1,
Does tillage reduce blackleg?
90
Significant effect
of tillage on
blackleg
incidence and
severity
(Carman,
Conventional
80
% incidence
70
60
50
40
Zero
30
20
10
0
CCCC CWCC CCWC CWFC
MB Guo et al.2005)
Does tillage reduce blackleg?
8
Significant
effect of tillage
on blackleg
incidence and
severity
(Carman,
Conventional
7
Severity (0
(0-9)
6
5
4
Zero
3
MB Guo et al.2005)
No sig. effect
(Melfort, SK Bailey et
al.2000)
2
1
Low disease
pressure
0
1994
1995
1996
1997
Does tillage reduce blackleg?
5
Severity (0
(0-5)
4
3
2
1
0
Significant
Conventional effect of tillage
Zero
on blackleg
incidence and
severity
No sig. effect
No tillage
effect, even
under higher
disease
pressure (Lange &
Kharbanda, 2002,
Viking, AB)
Effect of tillage on primary inoculum
Tillage buries shoot tissue, conservation
tillage leaves more tissue on surface
Non-linear relationship with surface
residue and blackleg disease (Turkington et al. 2000)
Burial encourages formation of
pseudothecia over pycnidia(Kharbanda & Ostashewski
1997)
Seeding operations bring residues to
surface
Burning crop residues
Fields burn unevenly
Low-moisture tissue burns, high moisture tissue
remains
Low moisture=upper stems, branches, etc
High moisture = stem bases, where
pseudothecia are concentrated
Raking + burning reduced ascospore release
(Australia, Khangura et al, 2007)
Atmospheric carbon, soil OM, air pollution, etc.
Burning
Many unburned areas
Burnt areas
What’s the real objective?
Ascospore load important determinant of
disease severity (Wherrett et al 2004):
>25×105 ascospores/stem maximizes disease
in adult plants
5×105 to 25×105 ascospores/stem reduces
disease incidence
Management objective: limit viable primary
inoculum on soil surface in susceptible
period
Can this be done without tillage in short
rotations?
Possible strategies to reduce Primary
inoculum without tillage
Mechanical
disruption of lower
stems
Mower, flail mower?
Stubble-applied
fungicides?
Sulphur,copper?
Stubble-applied
fertilizers
Enhance microbial
decomposition?
Possible strategies to reduce Primary
inoculum without tillage
Biological control by
antibiosis
Paenibacillus
polymyxa
Streptomyces
halstedii, S. rochei
Possible strategies to reduce Primary
inoculum without tillage
“Stubble degraders”
Cyathus olla
Ceriporiopsis
subvermispora/Cellul
omonas
sp./Azospirillum
brasilense
consortium
(sugarcane bagasse)
Summary
Reduction of canola rotational interval to less
than 1 crop/2 years unlikely in many areas
Switch from conservation tillage/zero tillage
unlikely or ineffective except in some areas
Need technologies that reduce inoculum load
in fields without relying on rotation or tillage