The main objective of this experiment was to evaluate the biopesticide Theia in programs with three applications of targeted, conventional fungicides for managing powdery mildew (FRAC 3 and 50) made early in disease development. Additional objectives were to evaluate Regev, a hybrid fungicide with tea tree extract plus difenoconazole, and to compare two FRAC 50 fungicides (Prolivo and Vivando).
The treatments were as follows:
- Untreated Control
- Theia 3 lb (1-8); Vivando 15.4 fl oz (3, 5); Proline 5.7 fl oz (4)
- Theia 1.5 lb (1-8); Vivando 15.4 fl oz (3, 5); Proline 5.7 fl oz (4)
- Theia 1.5 lb (1-8); Prolivo 5 fl oz (3, 5); Rhyme 7 fl oz (4)
- Vivando 15.4 fl oz (3, 5); Proline 5.7 fl oz (4)
- Vivando 15.4 fl oz (3, 5, 7); Proline 5.7 fl oz (4, 6); Procure 8 fl oz (8)
- Prolivo 5 fl oz (3-8)
- Regev 8.5 fl oz (3-8)
- Vivando 15.4 fl oz (3-8)
Based on comparison with the untreated control, all treatments numerically improved control of powdery mildew on upper leaf surfaces over what was achieved by the general disease maintenance management program implemented (chlorothalonil and/or copper weekly 13 July – 27 Aug). The three fungicide programs with Theia were not significantly better than the parallel program with two applications of a FRAC 50 fungicide (Vivando) and one application of a FRAC 3 fungicide (Proline): 61-72% vs 72% control based on AUDPC values. Vivando was significantly more effective than Prolivo based on AUDPC values: 86% vs 59% control; however, there were no significant differences in defoliation or fruit handle quality. The numerically most effective treatment was the grower-recommended program of Vivando applied in alternation with a FRAC 3 fungicide from powdery mildew onset through mid-September (6 applications): 96% control on lower leaf surfaces based on AUDPC values. This program also had one of the highest percentages of fruit with good handles, significantly better than the untreated control.
Application dates were 1=28 Jul, 2=3 Aug, 3=11 Aug, 4=17 Aug, 5=24 Aug, 6=1 Sep, 7=7 Sep, and 8=14 Sep. Powdery mildew symptoms were first seen on 14 Aug. Thus first 2 applications of Theia were preventive.
The following photos were taken on 22 September, 8 days after the 8th (last) application.
