What would be representative temperatures for shelf-life studies with biopesticides in tropical countries? Estimates through long-term storage of biocontrol fungi and calculation of mean kinetic temperatures

In many tropical countries, studies to determine the shelf-life of biopesticides for commercialization and storage without refrigeration have been conducted under mild (≤ 25 °C) temperature regimes. Are these temperatures representative of non-refrigerated rural deposits? To answer this question, we set up trials in five Brazilian geographical regions. Representative temperatures were estimated using two distinct approaches: (1) calculation of the mean kinetic temperature (MKT) inside packages stored in rural deposits for up to 19 months, and (2) comparison of germination counts of fungi (Beauveria bassiana and Trichoderma spp.) kept under these conditions with those of conidia kept at constant temperatures. MKTs calculated for deposits located in the Northern, Northeastern, Central-Western, Southeastern, and Southern regions were 28.0, 26.7, 23.6, 22.2, and 21.7 °C, respectively. For all regions, MKTs calculated for the long-term trials were very close (≤ 0.5 °C) to the values calculated for the year 2013. However, in certain periods, MKTs in the South and Southeast deposits were near 25 °C, whereas variations in other regions were minimal (≤ 0.6 °C). The less precise estimate of representative temperatures in rural deposits, based on germination counts of B. bassiana and T. harzianum, were in the 23.8–35.4 and 24.0–27.5 °C ranges, respectively, depending on the geographical region. Our results indicate that guidelines that propose 30 °C to be adopted for stability tests for pharmaceutical and food products in tropical countries must also be applied to biopesticides intended for country-wide commercialization and storage under non-refrigerated conditions in Brazil.