ABE 697 Seminar

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Evaluation of Sealed Silo Technology Under U.S.
Conditions
Dirk E. Maier, Professor, Dept. of Grain Science
and Industry Carlos Campabadal, State Extension
Leader Kingsly Ambrose, Assistant Professor,
Dept. of Grain Science and Industry Tom Phillips,
Professor, Dept. of Entomology Mark Casada,
Research Agricultural Engineer, USDA-ARS
CGAHR Sam Cook, M.S. Student, Dept. of Grain
Science
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Introduction
Comparative study between a sealed Australian
silo and a U.S. silo engineered after-market for
sealability

• Primary focus effectively reducing loss of gas
  fumigant in a U.S. bolted corrugated steel hopper
  bin and evaluating novel/ improved sealing
  materials and methods.
• Ideally, we hope to show sealed storage is a
  viable option for U.S. producers and bulk
  handlers to combat stored grain insect pests and
  phosphine resistance in those pests
• In addition, the Australian pressure standard,
  thermosiphon fumigation recirculation method, and
  pressure venting equipment will be evaluated.

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Introduction

• Phosphine-resistant populations of several stored
  grain insect species have recently been
  developing around the world including in the U.S.
  (Opit et al. 2012).
• If phosphine loses its ability to kill insect
  pests, grain producers and handlers will have a
  much more difficult (and expensive) time
  maintaining grain quality.

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Introduction
Phosphine resistance found in field strains
(Oklahoma) of Lesser Grain Borer and Confused
Flour Beetle
Comparison of lethal concentrations (ppm) required to kill 50, 90, and 95 of T. castaneum and R. dominica adults of susceptible strains and field-collected populations, after 3 days Comparison of lethal concentrations (ppm) required to kill 50, 90, and 95 of T. castaneum and R. dominica adults of susceptible strains and field-collected populations, after 3 days Comparison of lethal concentrations (ppm) required to kill 50, 90, and 95 of T. castaneum and R. dominica adults of susceptible strains and field-collected populations, after 3 days Comparison of lethal concentrations (ppm) required to kill 50, 90, and 95 of T. castaneum and R. dominica adults of susceptible strains and field-collected populations, after 3 days Comparison of lethal concentrations (ppm) required to kill 50, 90, and 95 of T. castaneum and R. dominica adults of susceptible strains and field-collected populations, after 3 days
Lethal Concentration Ratios Lethal Concentration Ratios Lethal Concentration Ratios
Populations compared No. conc. Groups LC50 LC 95 LC 99
Garfield Tc vs Susceptible Tc 36 20.71 63.38 118.65
Payne 1Rd vs Susceptible Rd 33 442.8 309.8 253.59
Logan Rd vs Susceptible Rd 33 98.72 409.62 909.57
Garfield Rd vs Susceptible Rd 33 161.19 678.55 1518.91

20 to gt1500 times more resistant than susceptible
(lab) strains!
Source Opit et al. (2012)
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Introduction

• Fumigating in unsealed (open top) bins has been
  cited as a main cause of this development. The
  vast majority of U.S. grain bins are not sealed
  for adequate levels of gas-tightness.
• Instead, bins must be sealed temporarily before
  fumigation, adding labor and material costs and
  resulting in greater risk of fumigation failures
  due to inadequate sealing

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Introduction

• Sealed bins and effective fumigation will help to
  prevent resistant strains of insects from
  developing, and will also prevent insects from
  re-infesting stored wheat.
• Therefore, research into best practices for
  manufacturing and construction of sealed bins is
  urgently needed.

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Objectives
1. Document and evaluate the materials
required to seal the U.S. hopper bin 2.
Demonstrate the gas-tightness of the U.S. hopper
bin using the pressure-decay half-life test 3.
Investigate the effectiveness of the U.S. sealed
bin when fumigating for control of stored wheat
insects 4. Validate the U.S. sealed bin as an
effective technology for pest control and grain
quality management 5. Apply and validate KSU
3D Ecosystem model for sealed hopper bins
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Objective 1
Document and evaluate the materials required to
seal the U.S. hopper bin

• Fumigation and recirculation equipment
• Pressure venting equipment
• Time and cost

• Sealants and rubber membranes
• Bin entry hatches
• Temp/moisture cable outlets

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Objective 1
Document and evaluate the materials required to
seal the U.S. hopper bin
Places to seal on steel silo
Roof vents Between wall panels Doors/hatches
Grain inlet/discharge Sidewall and eave/floor
junctions
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Objective 1
Evaluating thermosiphon recirculation
Black recirculation pipe is heated by the suns
rays
Temperature differential causes air movement
within the grain mass
Fumigant is dispersed evenly thru the grain mass,
maximizing insect exposure
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Objective 1
Evaluating thermosiphon recirculation

• Measure airflow rate and direction within pipe
• Monitor fumigant dispersion using
• - Thermosiphon
• - Fan-assisted CLF
• - No recirculation
• Evaluate usefulness in various weather conditions

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Objective 2
Demonstrate the gas-tightness of the U.S. hopper
bin using the pressure-decay half-life test

• This requires that a grain bin lose not more than
  half a given applied pressure (as measured by oil
  levels in the pressure relief tube) in under five
  minutes (Botta et al. 2012).
• Pressurization is easy to apply to a sealed bin
  with the aeration fan or an air compressor
  through a tire valve installed on the bin

1. Bin unpressurized
3. Pressure decayed by half (5 minutes)
2. Bin under full pressure
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Objective 3
Investigate the effectiveness of the U.S. sealed
bin when fumigating for control of stored wheat
insects
Insect bioassay cages Fumigation monitoring
points
Insector probes (OPI Systems) Temperature/moistur
e cables (OPI Systems)
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Objective 3

• Fumigation will be tracked with monitoring lines
  attached to temperature cables
• Fumigations will be carried out with
• Phosphine tablets
• Cylinderized phosphine (VaporPhos)
• Cylinderized sulfuryl fluoride (ProFume)
• Chlorine dioxide
• PH3-resistant insect strains will be used for
  bioassays (R. dominica and T. castaneum)
• Concentration x Time should be reached to kill at
  all life stages

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Objective 3
Cuballing, WA. Feb 2014. 100 m3 silo. Oats _at_ 7.4
mc, 35 C Phosphine _at_ 1.5 g/m3 (150 tablets)
(Approx 1060 ppm). Pressure½ gt 5 min
Source Chris Newman
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Objective 4
Validate the U.S. sealed bin as an effective
technology for pest control and grain quality
management

• Following fumigation trials, grain will be stored
  for 9-12 months and samples will be taken
  quarterly
• These quality characteristics will be measured
• Moisture content
• FGIS standards
• Milling and baking quality
• Mold and mycotoxins
• Grain temperature and moisture content monitored
  throughout, and controlled aeration will be used
  to manage grain quality

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Objective 5
Apply and validate KSU 3D Ecosystem model for
sealed hopper bins

• 3-dimensional heat, mass, momentum, and chemical
  transfer model using finite element method
• Predicts grain temperature and moisture content,
  interstitial air velocity, and fumigant
  concentration in stored grain
• Will apply to sealed hopper bin and incorporate
  thermosiphon recirculation

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Reasons to explore sealed grain storage

• Combat PH3 resistance
• Insects at all life stages killed
• Preserve grain quality
• Prevents re-infestation
• Can be used with controlled aeration
  to prevent shrink loss
• Increasing regulatory pressure
• Few approved fumigants remaining
• Greater worker safety
• Cost savings
• Fumigations are more effective, no top-offs
  required
• Less time and fewer materials to seal bin for
  subsequent fumigations
• Changing consumer preferences

Questions??
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Goal of grain storage Maintain grain quality
during the storage period
But
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Major Threats to Grain Quality
Fungi (Molds)
Insects
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• Many ways to control insects and mold
• Insecticides
• Aeration
• Grain chilling
• Cleaning grain

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• Fumigation
• Fumigant (PH3) released in silo
• Sufficient amount for certain time (Concentration
  Time Product, CTP)
• Must be sealed properly or gas will leak
• Sealing the silo is the only practical way to
  ensure a 100 kill of stored grain insects

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• Control failures
• Gas concentration and exposure time
  (Concentration Time Product) is insufficient to
  get 100 kill
• Susceptible insects are killed
• Selection pressure for genetically resistant
  insects
• Leaky structures are 1 reason for control
  failures and subsequent Phosphine resistance
  (Casada 2000)

https//sites.aces.edu/group/comm/newsline/Lists/P
osts/Post.aspx?ID61
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• Research needed
• More efficient economical sealing methods
• How sealed is enough? (standards)
• Engineering easy-to-seal silos