Effect of elevated atmospheric CO2 and temperature on the chemical and biological control of powdery mildew of zucchini and the Phoma leaf spot of leaf beet

The effects of increased temperature and CO2 levels on the effectiveness of four fungicides and one microbial treatment on disease development in zucchini-Podosphaera xanthii and leaf beet-Phoma betae pathosystems, kept under phytotron conditions, have been evaluated in this study. Six CO2 and temperature combinations have been tested for each pathosystem in four experimental trials. Penconazole and sulphur treatments, applied under a simulated CO2 and temperature increase scenario, have shown an efficacy in powdery mildew control that ranged from 85.0 to 88.9 % for penconazole and from 89.9 to 92.6 % for sulphur, and the treatments have therefore resulted to be equally effective compared to that observed under 400-450 ppm conditions. The disease control provided by A. quisqualis was significantly improved under an increased CO2 concentration of 800-850 ppm at 26-30 A degrees C, by 23.3 % for disease incidence and 22.8 % for disease severity. The effectiveness of both mancozeb and azoxystrobin against Phoma leaf spot is affected by high levels of CO2. The efficacy of mancozeb and azoxystrobin has been improved significantly by 15.3 % and 20.6 %, respectively, under 800-850 ppm of CO2 and 22-26 A degrees C, compared to the efficacy observed under standard conditions of CO2. More attention should be paid to the efficacy of chemical and biological control measures considering the predicted future climate changes.