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

The Theory Modified from Fields (1992) P.A.Eliopoulos

The Theory Factors that determine SPP susceptibility to cold Species Tribolium sp. and Oryzaephilus mercator  most susceptible P.A.Eliopoulos

The Theory Factors that determine SPP susceptibility to cold Species Trogoderma sp., Sitophilus sp., Ephestia sp., Plodia interpunctella  most tolerant P.A.Eliopoulos

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 P.A.Eliopoulos

The Practice Existing and potential technologies for cold treatments in storage facilities Ambient or forced-air aeration Chilled aeration Grain turning Freezing P.A.Eliopoulos

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 4- 8 silos. In cold regions cost and effectiveness comparable to chemical control P.A.Eliopoulos

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) P.A.Eliopoulos

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 P.A.Eliopoulos

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 P.A.Eliopoulos

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) P.A.Eliopoulos

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 P.A.Eliopoulos

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 P.A.Eliopoulos

Cold treatments Strategies P.A.Eliopoulos

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 P.A.Eliopoulos

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. P.A.Eliopoulos

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. P.A.Eliopoulos

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 P.A.Eliopoulos

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 P.A.Eliopoulos

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) P.A.Eliopoulos

Cold treatments Strategies Combination with acoustic detection friendly to human and environment simple and rapid method very high precision X limitations P.A.Eliopoulos

Cold treatments Strategies Combination with acoustic detection friendly to human and environment simple and rapid method very high precision X limitations P.A.Eliopoulos

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 P.A.Eliopoulos

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) P.A.Eliopoulos

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 P.A.Eliopoulos

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.