1. Panagiotis A. Eliopoulos
Practicality of using cold treatments for control of stored-product insect pests
Panagiotis A. Eliopoulos
Technological Educational Institute of Larissa Department of Plant Production
Greece

2. The Theory
Modified from Fields (1992)
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3. The Theory Factors that determine SPP susceptibility to cold Species
Tribolium sp. and Oryzaephilus mercator  most susceptible
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4. The Theory Factors that determine SPP susceptibility to cold Species
Trogoderma sp., Sitophilus sp., Ephestia sp., Plodia interpunctella  most tolerant
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5. The Theory Factors that determine SPP susceptibility to cold
Developmental stage – Age
Acclimation
Relative Humidity
Diapause
Cooling rate
Product moisture
Product type
Sex
Temperature level
Length of exposure
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6. The Practice
Existing and potential technologies for cold treatments in storage facilities
Ambient or forced-air aeration
Chilled aeration
Grain turning
Freezing
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7. Technologies for cold treatments Ambient aeration
Use of ambient air to cool the product
Very common method for cooling vertical and horizontal storages
Development of automated aeration control systems  maximize effectiveness and minimize energy costs
A simple automated aeration control unit costs ~ 3,000-4,000 $ and can be connected with silos.
In cold regions cost and effectiveness comparable to chemical control
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8. Technologies for cold treatments Ambient aeration
X Weather dependent
X Not effective in warm regions or when product is harvested during summer
X Estimation of cooling time needed for effective control is often a hard task
X High initial capital investment (perforated ducks, fans, automatic controller etc)
X Aeration may reduce grain moisture up to 1% that leads to weight loss and reduces profit
X Implementation is often complex and tricky (preparation, choosing of the proper fan, airflow rate, fan working hours, temperature monitoring etc)
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9. Technologies for cold treatments Chilled aeration
Use of refrigerated air when ambient air is not cool enough
In practice, temperature is lowering to pest’s development threshold (13-15oC)
Independent of weather conditions
Airflow 2-4 lt/sec/tone
Energy costs similar to insecticide treatment when cooling to 15oC
Cost can be competitive with other conventional pest management
Great variety of commercial units is available
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10. Technologies for cold treatments Chilled aeration
Most common units are trailer-based chillers connected with aeration system in large silos and flat storages
From Burks et al. 2000
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11. Technologies for cold treatments Chilled aeration
X Energy cost varies 3-12 Kwh/t
X High initial capital investment or rental fees
X Cost is often almost twice the cost of fumigation
X Condensation on the product can be a problem (reheating chilled air is often necessary)
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12. Technologies for cold treatments Grain Turning
Only when other cooling method is not available
Turning grain from one silo to another is a common method for temperature control
Warm grain is turned or mixed with cooler grain
It will break up “hot spots”
X The mean temperature will not change notably
X Danger of breakage of kernels (quality loss)
X Not an effective way to cool grain
X Average cost : 0,5% of grain value
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13. Technologies for cold treatments Freezing
Walk-in or chest-like freezers or refrigerators can be used to cool stored products
Can be a very good solution for disinfestation of small lots (e.g. processed food, quarantine treatment for imported packages)
Blast freezers (-20 to -30oC) have been also tested for larger amounts of stored products
X Cooling is very slow (minimal air circulation)
X The target temperature should be reached within the center of the bulk
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14. Cold treatments Strategies
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15. Cold treatments Strategies Whole Grain and Seeds
The most common method is chilled aeration
A chiller is attached to the aeration system of a storage structure (e.g. silo)
From Burks et al. 2000
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16. Cold treatments Strategies Whole Grain and Seeds
The main goal is to suppress insect population growth (target temperature 15oC)
Complete disinfestation is also possible under certain circumstances (target temperature 0 to - 10oC)
Combination of ambient aeration during fall and winter with chilled aeration during spring and summer.
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17. Cold treatments Strategies Dried Fruits and Nuts
Need for disinfestation immediately after harvest and before packaging
A very common strategy is freezing to rented blast freezers to -20 or more often -30oC (e.g. dried figs in USA, Turkey and Greece)
Tree nuts are often protected via ambient or chilled aeration systems.
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18. Cold treatments Strategies Processed and Packaged Foods
In case of infestation the package is moved into a freezer (-20oC) for disinfestation
Temperature levels and cooling times required for complete mortality are available for major SPP and most common foods.
X Cooling rate is often slow
X Monitoring of the core temperature inside the product is needed
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19. Cold treatments Strategies Empty Stores
In cold regions, the empty storage is opened up during winter and outside air is used to bring temperature below 0oC.
X Problems with inconsistent weather
X Subzero temperatures may have negative effects on equipment and machinery
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20. Cold treatments Strategies Combination with other IPM methods
Heat, Fumigation, Irradiation or other treatments are often followed by refrigerated storage in order to avoid reinfestation.
Cold treatments may extend the life of protectants (synthetic insecticides, IGR, DE, microbials etc)
Sanitation (thorough cleaning) can be integrated with cold treatment before cooling the commodity so as to eliminate residual insect infestations.
X Cannot be used simultaneously with fumigants or controlled atmospheres (less effective at low temperatures)
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21. Cold treatments Strategies Combination with acoustic detection
friendly to human and environment
simple and rapid method
very high precision
X limitations
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22. Cold treatments Strategies Combination with acoustic detection
friendly to human and environment
simple and rapid method
very high precision
X limitations
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23. Cold treatments Strategies Combination with acoustic detection
Project funded by EU and Greek funds
“DEVELOPMENT OF MODERN AND NOVEL METHODS OF INTEGRATED PEST MANAGEMENT AGAINST STORED PRODUCTS PESTS”
testing acoustic detection in a plethora of pest species, commodities and other factors.
3-year project, € 100,000 budget
until now acoustic emissions of 10 species have been recorded and analzyed
acoustic detection can become a very reliable detection method
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24. Conclusion Few risks for operators No residues on the product
Effective against insecticide – resistant populations
Easily combined with other IPM methods (sanitation, heat, insecticides etc)
Low temperature storage improves product quality and shelf life
Freezing does not have detrimental effect on product quality
X Cost not competitive with fumigation
X Cost of equipment and energy cannot be afforded by small farmers
X Dependent on cool ambient air
X Temperature lowering often not rapid (allows acclimation of pest)
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25. Future Research Needs
Need for more data on cold-hardiness of major SPP (basic research)
LT50 and LD50 (lethal times and doses needed for 50% pest population mortality) should be estimated via probit analysis
Research on blocking cold acclimation (e.g. using ice-nucleating bacteria)
Lab studies often underestimate cold-hardiness (not taking into consideration acclimation and the real temperature in the core of the bulk)
Energy efficient technologies should be considered in order to reduce cost
Effect on product quality (other than grain)
Detailed cost/benefit analyses
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26. Practicality of using cold treatments for control of stored-product insect pests
Present research is implemented through the Operational Program "Education and Lifelong Learning" and is co-financed by the European Union (European Social Fund) and Greek national funds.