Efficacy of azoxystrobin for the control of cucumber downy mildew (Pseudoperonospora cubensis) and fungicide residue analysis

• Azoxystrobin effectively controlled cucumber downy mildew (CMD).
• Azoxystrobin significantly increased yield when compared to the untreated control.
• Negative correlation was found between CMD severity and yield.
• Pre-harvest interval for azoxystrobin is adequately regulated.
• Residues in the treated cucumbers were below MRL up to four days after application.

During a five-year trial (2007–2011), the efficacy of azoxystrobin (Quadris, 250 g a.i. L−1, Syngenta) in two doses (187.5 g a.i. ha−1 and 250 g a.i. ha−1) and chlorothalonil (Bravo 720-SC, 720 g a.i. L−1, Syngenta) at a rate of 1.44 kg a.i. ha−1 was tested for the control of cucumber downy mildew (CDM). Cultivars that were susceptible or resistant to CDM (Regal and Haros, respectively) were tested for their response to fungicide applications. Differences in both disease severity and yield of the cultivars among resistance levels and fungicide treatments were observed. A highly significant and negative correlation was obtained between AUDPC and yield. Higher yields can be achieved by planting more resistant cultivars in combination with lower doses of fungicides. This is an indication that CDM contributes significantly to yield losses in cucumber production in Serbia. While monitoring the degradation of azoxystrobin residues, a decrease in residue levels to 1.0 mg kg−1 below the maximum residue level (MRL) was observed at the end of the pre-harvest interval (PHI).