The effects of ozone treatments on the agro-physiological parameters of tomato plants and the soil microbial community.

Ozone has been applied in many processes (drinking water disinfection and wastewater treatment, among others) based on its high degree of effectiveness as a wide-spectrum disinfectant and its potential for the degradation of pollutants and pesticides. Nevertheless, the effects of irrigation with ozonated water on the soil microbial community and plant physiology and productivity at the field scale are largely unknown. Here, we assessed the impact of irrigation with ozonated water on the microbial community of a Mediterranean soil and on Solanum lycopersicum L. agro-physiology and productivity in a greenhouse experiment. For this purpose, we evaluated: i) soil physicochemical properties, soil enzyme activities, and the biomass (through analysis of microbial fatty acids) and diversity (through 16S rRNA gene and ITS2 amplicon sequencing) of the soil microbial community, and ii) the nutrient content, physiology, yield, and fruit quality of tomato plants. Overall, the soil physicochemical properties were slightly affected by the treatments applied, showing some differences between continuous and intermittent irrigation with ozonated water. Only the soil pH was significantly reduced by continuous irrigation with ozonated water at the end of the assay. Biochemical parameters (enzymatic activities) showed no significant differences between the treatments studied. The biomasses of Gram- bacteria and fungi were decreased by intermittent and continuous irrigation with ozonated water, respectively. However, the diversity, structure, and composition of the soil microbial community were not affected by the ozone treatments. Changes in soil properties slightly affected tomato plant physiology but did not affect yield or fruit quality. The stomatal conductance was reduced and the intrinsic water use efficiency was increased by continuous irrigation with ozonated water. Our results suggest that soil health and fertility were not compromised, however ozonated water treatments should be tailored to individual crop conditions to avoid adverse effects.

Enhanced degradation of spiro-insecticides and their leacher enol derivatives in soil by solarization and biosolarization techniques.

The leaching potential of three insecticides (spirodiclofen, spiromesifen, and spirotetramat) was assessed using disturbed soil columns. Small quantities of spirodiclofen and spiromesifen were detected in leachate fraction, while spirotetramat residues were not found in the leachates. In addition, the transformation products (enol derivatives) are relatively more mobile than the parent compounds and may leach into groundwater. Moreover, the use of disinfection soil techniques (solarization and biosolarization) to enhance their degradation rates in soil was investigated. The results show that both practices achieved a reduction in the number of juvenile nematodes, enhancing in a parallel way degradation rates of the insecticides and their enol derivatives as compared with the non-disinfected soil. This behavior can be mainly attributed to the increase in soil temperature and changes in microbial activity. All insecticides showed similar behavior under solarization and biosolarization conditions. As a consequence, both agronomic techniques could be considered as suitable strategies for detoxification of soils polluted with the studied pesticides.

Cross-resistance and baseline susceptibility of Mediterranean strains of Bemisia tabaci to cyantraniliprole.

BACKGROUND: The whitefly Bemisia tabaci Gennadius is a severe pest in many field and greenhouse crops worldwide and has developed resistance to insecticides from most chemical classes. The ease with which this pest develops resistance makes it essential to incorporate new compounds with different modes of action and no cross-resistance with those previously used into insecticide resistance management strategies. To that end, the systemic effect of the new diamide cyantraniliprole was tested with multiresistant, selected and field populations of Q-biotype B. tabaci from the Mediterranean area. RESULTS: Bioassays with multiresistant and laboratory-selected populations indicated no cross-resistance to cyantraniliprole in the B. tabaci strains exhibiting resistance to other insecticides. The LC50 values for nymphs from 14 field populations varied between 0.011 and 0.116 mg L(-1), a 10.5-fold natural variability. The LC50 values for adults from three strains ranged from 0.060 to 0.096 mg L(-1). CONCLUSION: These baseline data will be helpful for monitoring future potential shifts in susceptibility to cyantraniliprole in Mediterranean whitefly populations within an IRM programme. Cyantraniliprole may play an important role in mitigating insecticide resistance in B. tabaci because of its high efficacy and its lack of cross-resistance to other insecticides, even in multiresistant Q-biotype populations collected from a highly problematic insecticide resistance area.