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

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.

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.

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

Populations compared Garfield Tc vs Susceptible Tc No. conc. Groups 36 Lethal Concentration Ratios LC50 LC 95 LC 99 20.71

63.38

118.65

Payne 1Rd vs Susceptible Rd Logan Rd vs Susceptible Rd 33 33 442.8

98.72

309.8

409.62

253.59

909.57

Garfield Rd vs Susceptible Rd 33 161.19

678.55

1518.91

20 to >1500 times more resistant than susceptible (lab) strains!

Source: Opit et al. (2012)

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

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.

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

Objective 1

Document and evaluate the materials required to seal the U.S. hopper bin • Sealants and rubber membranes • Bin entry hatches • Temp/moisture cable outlets • Fumigation and recirculation equipment • Pressure venting equipment • Time and cost

Objective 1

Document and evaluate the materials required to seal the U.S. hopper bin Places to seal on steel silo: Grain inlet/discharge Sidewall and eave/floor junctions Roof vents Between wall panels Doors/hatches

Objective 1

Evaluating thermosiphon recirculation

Black recirculation pipe is heated by the sun’s rays Temperature differential causes air movement within the grain mass Fumigant is dispersed evenly thru the grain mass, maximizing insect exposure

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

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 2. Bin under full pressure 3. Pressure decayed by half (5 minutes)

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/moisture cables (OPI Systems)

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 • PH 3 -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

2000

Objective 3

Cuballing, WA. Feb 2014. 100 m 3 Phosphine @ 1.5 g/m 3 silo. Oats @ 7.4% mc, 35 ° C (150 tablets) (Approx 1060 ppm). Pressure½ > 5 min

1800 1600 1400 1200 1000 800 600 400 200 0

Headspace Wall west Base

Day of fumigation

Source: Chris Newman

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

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

Reasons to explore sealed grain storage

• Combat PH 3 • 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??