First application in France of heat disinfestation of a large wheat mill

Abstract: Thermal disinfestations of flour mill structures and equipment were traditionally used before the 1960’s, but they have been replaced by methyl bromide fumigation until the international ban of methyl bromide in 2005. During the last decade, heat disinfestation of flour mills was developed in Northern America and in some European countries from the 2000’s workshops of heat disinfestation of wheat mills were carried out. In France, the first industrial application of this technology was attempted in 2010 for the disinfestation of a large wheat mill and was carried out by Agronet Company in collaboration with INRA Research Laboratory in Bordeaux. The heating of the flour mill was performed from electric heat generators of Thermonox® technology (Germany). The electric heaters are forced heat air ventilators enabling to reach the target temperature of 50 to 55 °C in about 10-12 h in all parts of the mill. Then, temperature is maintained at this level during 24 to 36 h and optimized from the indications of temperature sensors in order to obtain complete mortality of insects, whatever their development stage. Encaged insects (Tribolium castaneum and Rhyzopertha dominica) placed in the mill during mill heating were killed at more than 97%. Very few survivals were only observed on the floor at the ground level of the mill. The reproductive capacity of individuals surviving thermal exposure was severely reduced. This first industrial application of heat disinfestation process to a large wheat mill confirmed the results of laboratory studies performed earlier at INRA Laboratory. The economic evaluation of the heat treatment in the conditions described above revealed that it is competitive compared to fumigation with similar requirements in the preparation of the building before treatment. This technology seems very promising for periodic eradication of insect colonies in cereal processing industries without use of pesticide.