Successful management of strongly phosphine resistant stored grain pests by developing Sulfuryl fluoride as an alternative fumigant Manoj Nayak Principal Research Scientist DAFF-QLD biosecurity built on science Cooperative Research Centre for National Plant Biosecurity
Background Industry needs a ‘phosphine-resistance-breaker’ Immediate need to tackle flat grain beetles Sulfuryl fluoride (ProFume®) currently registered Fumiguide® does the calculation!
Very limited literature No Australian studies
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CRC50172: Aim and Objectives Develop SF as an alternative to phosphine Establish relationship between concentration and exposure periods (C x T) at 15 and 25ºC Recommend fumigation protocols for strongly phosphine resistant pests Validate through large scale field trial
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Research Team DAFF (DEEDI) Manoj Nayak, Pat Collins, Raj Jagadeesan, Hervoika Pavic, Lawrence Smith, Linda Bond
GrainCorp Robin Reid, Barry Reardon, Peter Egart
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Materials and Methods
Development of CT (mg-h/L)
SF (99.8%) Conc. (mg/L) X Time (hours) Four key resistant pest spp. Fumigations in glass desiccators Gas Chromatograph for monitoring and top-up Population extinction (all life stages) Approx. time to develop one CT: 3 months biosecurity built on science
Four Key Pest Species Strongly phosphine resistant populations Flat grain beetle (FGB: Cryptolestes ferrugineus) Lesser grain borer (LGB: Rhyzopertha dominica) Rust-red flour beetle (RFB: Tribolium castaneum) Rice weevils (RW: Sitophilus oryzae)
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Response of RFB (T. castaneum) to SF Life stage
Lethal conc. mg/L (LC99.9) at 48 hrs
CT Product
Tolerance factor over adult
Egg
75
3600
50x
Early Instar
1.5
72
1x
Mid Instar
1.5
72
1x
Late Instar
1.5
72
1x
Pupa
1.5
72
1x
Adult
1.5
72
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CT Products Developed at 25ºC Exposure period in hours (days)
Conc. (mg/L)
96 (4)
6.64 8.3 12.5 15 18
144 (6) 240 (10)
CT Products
FGB
LGB
RFB
RW
X √ √ √ √
√ √ √ √ √
X X X X X
X X X X X
√
√
√
√
√
√
(mg-h/L)
10 8.3
640 800 1200 1440 1730
1440 1992
√ √
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CT Products Developed at 15ยบC FGB
LGB
RFB
RW
750
X
X
X
X
16
1500
X
X
X
X
1.66
400
X
X
X
X
3.3
800
X
X
X
X
4.16
1000
X
X
X
X
Exposure period in hours (days)
Conc. (mg/L)
96 (4)
8
240 (10)
CT Products (mg-h/L)
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Phosphine-R Shows No Cross-R to SF 100
Adult mortality (%)
80
RFB-S
60
RFB-SR RW-S RW-SR LGB-S LGB-SR FGB-S FGB-SR
40
20
0 0
2
4 6 Lethal Time (hours)
8
10
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% Sorbed
Sorption of SF by Different Commodities (from 2 mg/L) 100 90 80 70 60 50 40 30 20 10 0
1 Day 2 Days 10 Days
Wheat
Sorghum
Sunflower
Rolled Oats
Commodities
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Overview of Results From most susceptible to most tolerant: LGB = FGB > RW > RFB Trend consistent across all CTs ‘T’ has greater influence than ‘C’ on efficacy Significant reduction in efficacy at lower temperatures Data comparable to published reports Phosphine resistance shows no cross resistance to SF Sorption a major issue biosecurity built on science
Field Validation of SF fumigation Bunker (87m long and 37m wide) 8000 t of AUH2 wheat Pre and post fumigation assessments of natural infestations SF fumigation in March 2011 @ 40 g/m3 (7-8 entry points) Target CT: 1500 (highest registered rate)(>10days) Full clearance of gas in early April biosecurity built on science
Bunker Trial‌.
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Sampling Protocol 23 sampling points 600-800g sampled (150 cm depth) One sampling at
a month before fumigation just before fumigation after clearance of gas monthly after clearance (4)
Temp. and moisture content of grain (150 cm.) Lab assessment: live adults and progeny (8-weeks)
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Sampling Points in a Bunker 1-12: outer edges, 13-20: sides, 21-23: top
12
1 13
11Ga 20 Gas s
21 19
10
9
2
3
14
15
22
4
16
23
18
17
8
7
5
6
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Temperature and Moisture Content Profiles of Grain Average day-time temperature range (ºC)
Pre-fumigation-March
26 - 35
Post-fumigation-April
24 - 34
Post-fumigation-May
22 - 30
Post-fumigation-June
22 - 30 Average grain moisture content range (%)
Pre-fumigation-March
11.9 – 12.9
Post-fumigation-April
11.4 – 12.5
Post-fumigation-May
12 - 12.8
Post-fumigation-June
11.7 - 12.8 biosecurity built on science
Infestation Profile (live insects) Total Numbers
1000 FGB
800
RFB
600
LGB
400
SGB PSO
200
RW
0 Pre-fumi Post-fumi- Post-fumi- Post-fumi(Feb-Mar) Apr May June
Sampling Period
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Pest Distribution Pattern: Pre-fumigation
Mean numbers
350 300
FGB RFB LGB SGB PSO RW
250 200 150 100 50 0 Outer edges
All sides
Top
Infestation location
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Total numbers
Pest Profile (all dead): Post-fumigation 1600 1400 1200 1000 800 600 400 200 0
FGB RFB LGB SGB PSO RW April
May
June
Sampling period
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Pest Distribution Pattern (all dead): Post-fumigation (April)
Mean numbers
250 200
FGB
150
RFB LGB
100
SGB
50
PSO RW
0 Outer edges
All sides
Top
Infestation location
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Overview of Results SF fumigation successfully controlled all pest spp. Most important outcome: control of StR-FGB No live infestation detected for 4 months
(established through our sampling and on-site detection by storage staff)
No survivors from the original infestation (parents and progeny both controlled) Re-infestation (invasion) did not occur
Top of bunker favoured for infestation (dominated by FGB and Psocids) biosecurity built on science
Recent trend in strongly phosphine resistant FGB populations in central storages SF 60
Populations diagnosed
50 Northern NSW
40
South-East QLD
30 Central QLD
20 TOTAL
10 0 2007
2008
2009
2010
2011
2012
Monitoring Years
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Conclusions SF has excellent potential as an alternative (fits well to current FGB Eradication Plan) Current registered rate (1500 CT) adequate (fumigation period should be >6 days) Significant benefit to the industry Industry needs to use it strategically! biosecurity built on science
Key Questions What Strategy to Adopt? To allow egg control
Long exposure: minimum of 6 days Short exposures: very high conc. needed
How Many Fumigations? (R-management/environment/residue issues) only use where phosphine fails (eg. FGB problem)? use in between phosphine? limit number of fumigations?
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Future Research Efficacy at higher temperatures (30◦C, 35◦C) Recommendation Table for Industry Explore partner fumigants for synergism Determine ‘time to reinfestation’ by pests after treatments (farm, central storage) Develop resistance testing protocol biosecurity built on science
Thank you  For more information, please email [manoj.nayak@deedi.qld.gov.au]
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