White blister rust

•Albugo candida – oomycete, biotroph•Affects broad-acre oilseed and vegetable crops and weeds in Brassicaceae

•Reduces yields in oilseeds and vegetables•Broccoli, Brussels sprouts – marketable plant organs•On commercial broccoli crops- not reported in Australia until the disease outbreak in 2001

Symptoms

• Blisters (sori) under epidermis of aerial host organs - local infections, airborne zoosporangia

• Hypertrophy and hyperplasia of host organs- systemic infections, oospores,

• Known to cause lesions on roots

Disease control

• Oomycete specific fungicides – acylalanine, strobilurin• Protectant fungicides – copper-based most effective• Combination of systemic and protectant• BrassicaSPOT

™ perdictive model• Resistant varieties• Cultural methods: crop rotation, irrigation, production of

seedling in disease free areas• Rapid adaptation of A. candida in intensive production systems

- low level of genetic diversity - extensive use of systemic fungicides

5

Study Aim

• Identify alternatives to conventional fungicides for white blister rust management

• Evaluate alternatives in combination with resistant varieties in glasshouse and field

6

Glasshouse experiments:•B. rapa cvs ‘Waltz’ and ‘Seven Gates’

•B. oleracea cvs ‘Greenbelt’ and ‘Viper’

•4 alternatives of different action mode:1. surfactant – non-ionic2. polymer –antitranspirant3. film-forming bacterium4. SAR activators

•unsprayed control & standard industry practice

•Inoculations with A. candidaspecific to B. rapa & B. oleracea

Alternatives for white blister rust control on B. rapa & B. oleracea vegetables

7

• disease levels did not differ significantly from control (Du-Wett™, Nu-Film™)

• Bacillus subtilis – less effective than Bion® and Amistar®

• Bion® – effective as Amistar®

• severe phytotoxicity on seedlings of both cultivars

Results – B. rapa

Incidence of white blister rust on seedlings of B. rapa cvs Waltz and Seven Gates in a glasshouse experiment

0

5

10

15

20

25

unsprayed Du-Wet Nu-Film B.subtilis Amistar Bion

% o

f see

dlin

gs w

ith b

liste

rs

Waltz 7Gates

8

• disease levels did not differ significantly from control (Du-Wett™, Vapor Gard™)

• Bion®, B. subtilis– effective as Amistar®

• no phytotoxicity of Bion® on seedlings of both cvs

• slight toxicity of Vapor Gard™

Results – B. oleracea

Incidence of white blister rust on seedlings of broccoli cvs "Greenbelt' and "Atomic" in a glasshouse experiment

0

20

40

60

80

100

Gre

enbe

lt

Ato

mic

Gre

enbe

lt

Ato

mic

Gre

enbe

lt

Ato

mic

Gre

enbe

lt

Ato

mic

Gre

enbe

lt

Ato

mic

Gre

enbe

lt

Ato

mic

unsprayed Du-Wet VaporGard Bion B. subtilis Amistar

% o

f dis

ease

d se

edlin

gs

9

Field experiments:Crops•B. rapa ‘Matilda’ – Gatton, QLD

•B. oleracea ‘Rumba’ and ‘Grevillea’ - Werribee South and Rosebud, VIC

Treatments•alternatives: B. subtilis,

Streptomeces lydicus, Bion®, sodium lauryl sulfate

•control - unsprayed

•standard industry practice

Alternatives for white blister rust control in the field

10

Field trial – Chinese cabbage

0

0.5

1

1.5

2

2.5

3

3.5

4

Amistar B.subtilis Bion 10 Bion 1 Control

Mea

n se

verit

y of

whi

te b

liste

r rus

t on

plan

ts (0

-4)

•None of the treatments controlled white blister rust on Chinese cabbage ‘Matilda’

•Evidence for possible strobilurin resistance in A. candida specific to B. rapa

11

Field trial – broccoli ‘Rumba’

•White blister rust severity – significantly lower on plants sprayed according to grower program (TriBase Blue® –weekly, Amistar® added at week 4, 7 &10

•No disease on heads

0

10

20

30

40

50

60

Control Bion (2) B. subtilis (11) Grower Program (11)

Plan

ts w

ith le

aves

with

blis

ters

(%) Lsd (5%) = 14.6

12

Field trial – broccoli ‘Grevillea’

•Bars in different colours – treatments differ significantly (5%)

•Numbers in brackets – number of sprayed applied

0

10

20

30

40

50

60

70

80

Control SLS (9) S. lydicus (9) Standard (13)

Inci

denc

e of

whi

te b

liste

r rus

t on

head

s (%

)

13

• None of alternatives were as effective as conventionalchemicals

• Bion® – effective on broccoli seedlings at rates reduced100x

• Bion® – phytotoxic to pak choi and Chinese cabbageseedlings

• B. subtilis, S. lydicus and SLS – effective on broccoli (heads)

• Alternatives are valuable options for white blister rustcontrol on seedlings and broccoli heads

Conclusions

•Horticulture Australia Limited•Vegetable Growers of Australia•Victorian Department of Primary Industries•Department of Employment Economic Development and Investment,Queensland

•Federal Government•Seed companies and alternative treatment suppliers

Acknowledgements