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To maintain market access, the Australian grain industry urgently requires a cost-effective, market accepted alternative to the fumigant phosphine, which is now threatened by high level resistance in insect pests. Currently, the only practical candidate is the fumigant sulfuryl fluoride (SF) which, although registered, has not been developed for use on stored grain. There is an urgent need to develop this fumigant as a resistance management tool and at the same time, ensure that rates used by industry are as low as practicable.
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Successful management of strongly phosphine resistant stored grain pests by developing Sulfuryl fluoride as an
alternative fumigant
Cooperative Research Centre for National Plant Biosecurity
Manoj Nayak Principal Research Scientist
DAFF-QLD
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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
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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 Early Instar Mid Instar Late Instar Pupa Adult
75 1.5 1.5 1.5 1.5 1.5
3600 72 72 72 72 72
50x 1x 1x 1x 1x -
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CT Products Developed at 25ºC
Exposure period in hours (days)
Conc. (mg/L)
CT Products
(mg-h/L) FGB LGB RFB RW
96 (4) 144 (6) 240 (10)
6.64 8.3 12.5 15 18 10 8.3
640 800 1200 1440 1730 1440
1992
X √ √ √ √ √ √
√ √ √ √ √ √ √
X X X X X √ √
X X X X X √ √
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CT Products Developed at 15ºC
Exposure period in hours (days)
Conc. (mg/L)
CT Products
(mg-h/L)
FGB LGB RFB RW
96 (4) 240 (10)
8 16 1.66 3.3
4.16
750 1500 400 800
1000
X X X X X
X X X X X
X X X X X
X X X X X
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Phosphine-R Shows No Cross-R to SF
0 2 4 6 8 10Lethal Time (hours)
0
20
40
60
80
100Ad
ult m
orta
lity (%
)
RFB-SRFB-SRRW-SRW-SRLGB-SLGB-SRFGB-SFGB-SR
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Sorption of SF by Different Commodities (from 2 mg/L)
0102030405060708090
100
Wheat Sorghum Sunflower Rolled Oats
Commodities
% S
orbe
d 1 Day
2 Days
10 Days
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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
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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
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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
22
Gas
21
2 4
23 Gas 11
1 12
10
20
14
13
19
8
18
17
16
5
15
6
9 7
3
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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
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Infestation Profile (live insects)
0
200
400
600
800
1000
Pre-fumi(Feb-Mar)
Post-fumi-Apr
Post-fumi-May
Post-fumi-June
Sampling Period
Tota
l Num
bers FGB
RFBLGBSGBPSORW
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Pest Distribution Pattern: Pre-fumigation
0
50
100
150
200
250
300
350
Outer edges All sides Top
Infestation location
Mea
n n
um
ber
s FGBRFBLGBSGBPSORW
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Pest Profile (all dead): Post-fumigation
0200400600800
1000120014001600
April May JuneSampling period
To
tal n
um
bers
FGBRFBLGBSGBPSORW
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Pest Distribution Pattern (all dead): Post-fumigation (April)
0
50
100
150
200
250
Outer edges All sides Top
Infestation location
Mea
n nu
mbe
rs FGBRFBLGBSGBPSORW
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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)
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Recent trend in strongly phosphine resistant
FGB populations in central storages
0
10
20
30
40
50
60
2007 2008 2009 2010 2011 2012
Popu
latio
ns d
iagn
osed
Monitoring Years
Northern NSW
South-East QLD
Central QLD
TOTAL
SF
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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!
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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
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