integrated management of phytophthora root rot of papaya ... · research into the integrated...
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Department of Employment, Economic Development and Innovation
INTEGRATED MANAGEMENT OF PHYTOPHTHORA ROOT ROT OF PAPAYA IN THE WET TROPICS OF
FAR NORTH QUEENSLAND, AUSTRALIA
2© The State of Queensland, Department of Employment, Economic Development and Innovation, 2010
•Location:•Mossman-Tully, (50%) of total production. •(200 ha - 8,400 tonne of fruit)
•Av. plantation size - 2 ha.
•Limitations: cyclones, pests and diseases - Phytophthora root & fruit rot, foliar diseases.
‘Wet Tropics’ papaya growing area
3© The State of Queensland, Department of Employment, Economic Development and Innovation, 2010
• high rainfall (3600 mm)
• frequent high intensity downpours
• ~ 75% occurs December–April
Rainfall in the papaya growing area of the wet tropical coast
0100200300400500600700800
Jan Feb Mar April May Jun Jul Sep Oct Nov Dec
4© The State of Queensland, Department of Employment, Economic Development and Innovation, 2010
Phytophthora diseases of papaya in Australia
Phytophthora fruit rot Basal trunk rot
Phytophthora root rot
5© The State of Queensland, Department of Employment, Economic Development and Innovation, 2010
The Pathogen (Phytophthora palmivora)
General Biology
Distinguishing Features
Papillate, ellipsoid to ovoid, deciduous sporangia with short pedicels
Globose to subglobose chlamydospores or resting structures
obvious papilla
ellipsoid sporangia
chlamydospore
short pedicel
Parasitic on over 1000 plant species, including major food crops, forest trees, sub-tropical and tropical fruits, berries and ornamentals
6© The State of Queensland, Department of Employment, Economic Development and Innovation, 2010
Research into the integrated management of Phytophthora root rot of papaya in north Queensland
1) Use of mounds and surface mulches
2) Field and glasshouse evaluation of metalaxyl-M and potassium phosphonate
3) Screening for Phytophthora resistance
7© The State of Queensland, Department of Employment, Economic Development and Innovation, 2010
Use of mounds and surface mulches
Mound/organic mulch
Flat/organic mulch
Mound/plastic mulch
Flat/plastic mulch
8© The State of Queensland, Department of Employment, Economic Development and Innovation, 2010
0
10
20
30
40
50
60
70
Mounds Flat ground
% p
lant
s with
roo
t rot
a
b
0
10
20
30
40
50
60
Plastic Bare ground Organic mulch
% p
lant
s with
roo
t rot
a
bb
Mounds
• best survival
• highest yield
• best tree vigour
Overall effects of mounds and mulches at harvest
Mulches
Plastic - best survival
- highest yield
- best tree vigour
**Bars followed by the same letter are not significantly different
9© The State of Queensland, Department of Employment, Economic Development and Innovation, 2010
0 10 20 30 40 50 60 70 80 90
Flat/bare soil
Flat/organic mulch
Flat/plastic mulch
Mound/bare soil
Mound/organic mulch
Mound/plastic mulch
Percentage papaya at harvest with root rot when grown on mounds or flat ground, with or without organic and plastic
mulches
% plants with root rot
a
a
a
a
b
b
**Bars followed by the same letter are not significantly different
10© The State of Queensland, Department of Employment, Economic Development and Innovation, 2010
1
2
3
4
5
6
7R
oot r
ot se
veri
ty
1.25 0.625 0.312 Infested control
Root rot severity assessed on a 1-7 scale of increasing disease severity
Glasshouse study of the effect of metalaxyl-M on root rot severity in papaya
In field:
Metalaxyl-M as Ridomil Gold®
at 1 kg/100 m of row
a a
b
c
**Bars with the same letter are not significantly different
g a.i./m2
11© The State of Queensland, Department of Employment, Economic Development and Innovation, 2010
Untreated Metalaxyl-M
Metalaxyl-M (Ridomil Gold®)
12© The State of Queensland, Department of Employment, Economic Development and Innovation, 2010
Untreated
Metalaxyl-M
13© The State of Queensland, Department of Employment, Economic Development and Innovation, 2010
Plant age x rates of phosphonate (AgriFos 600®)Plant age (weeks) Rates of potassium phosphonate (g a.i./L)
0 3 6 128 7.0 c 7.0 c 7.0 c 7.0 c12 7.0 c 7.0 c 6.8 c 7.0 c
16 5.2 b 5.4 b 3.0 a 2.2 a
Root rot severity assessed on a 1-7 scale of increasing disease severity
14© The State of Queensland, Department of Employment, Economic Development and Innovation, 2010
0
20
40
60
80
100
% p
lant
surv
ival
Treatments
Effect of metalaxyl-M and phosphonate alone and in combination on the survival of papaya at harvest
Metalaxyl-M+phosphonate Phosphonate
Metalaxyl-M Untreated
a
abb
c
15© The State of Queensland, Department of Employment, Economic Development and Innovation, 2010
Screening for Phytophthora resistance - susceptibility of 62 papaya cultivars and breeding lines
01020
3040
5060
7080
90100
Paris*NT RedSubang 6Paris*Sunrise (RB1)Subang*SunriseSaipan RedLine 1BNT Red
* The other 55 cultivars fell between Saipan Red and NT Red
% m
orta
lity
LSD = 5%
16© The State of Queensland, Department of Employment, Economic Development and Innovation, 2010
South Johnstone RS trial post Cyclone Larry
Phosphonate treated plot
Untreated plot