The impact of plastic mulches on Aspergillus flavus-clade populations in pistachio orchard soils

Plastic mulches on the soil surface can impact the population and activity of soil microorganisms, such as Aspergillus species, by altering the temperature and humidity of the soil. In the present study, the effects of white and black mulches were examined on the population of Aspergillus flavus-clade in the soils of two pistachio orchards (35-year-old Fandoghi cultivar) with a surface drip irrigation system in Rafsanjan (Kerman Province, Iran). The experiment was performed as a randomized complete block design with three replications. The population of A. flavus-clade in the soil was measured monthly using the serial dilution method and SPDA culture medium. Identification and toxigenic isolates were screened using a coconut agar medium. The results indicated that white and black plastic mulches decreased the population density of A. flavus-clade in all sampling months except for December in the two pistachio orchards. In garden No. 1, the population of A. flavus-clade decreased 64 and 46 percent in August compared to the control in black and white mulches, respectively. However, in garden No. 2, this reduction was 48 and 35% in black and white mulches, respectively. Additionally, in plastic mulches, mainly black mulch, the population of toxigenic isolates exhibited a significant decrease in the soil compared to the control, especially during hot months. It is concluded that using plastic mulches, mainly black mulches, can reduce the population of A. flavus-clade in pistachio orchard soils and minimize contamination of pistachios with Aspergillus and aflatoxin.