Evaluation of fogging devices for BCO application in fruit cold storage rooms

The use of biological control organisms (BCOs) constitutes an alternative to chemical pre- and post-harvest treatments which are currently used for the control of storage diseases of pome fruit. In this study, we aimed at developing an appropriate application technique for these BCOs using cold fogging devices.
Four commercially available cold fogging devices were tested using different settings. Characteristics and performances of the machines were measured. The produced spray plume of each fogger was fully characterized by measuring droplet sizes, droplet velocities and spray angle using a PDPA laser. The produced air flow velocities were measured using a hotwire anemometer. Liquid flow rate was determined by measuring the weight difference of the solution in the tank before and after spraying a predefined duration. Secondly, the performance of the foggers in terms of spray distribution and deposition was measured in a cold storage loaded with 33 bins filled with apples. Nine bins were sampled, using filter-paper wrapped apples. Mineral chelates were applied as tracer liquid.
The measuring results reflect important differences in spray characteristics between the different techniques. For example, the average droplet size ranged between 10 and 70 µm. Devices producing a smaller droplet size spectrum showed higher average depositions on the fruit in the cold storage. A high variation in deposition values was observed between the sampled bins.