Fungicide and cultivar control of Septoria diseases of wheat

Abstract

Single applications of triazole fungicides propiconazole (125 g ha −1), tebuconazole (125 g ha −1) and cyproconazole (120 g ha −1) were equally effective in reducing Septoria nodorum and increasing yield on the spring wheat cultivar Aroona, which is moderately susceptible to the pathogen. A single application of propiconazole (125 g ha −1) at head emergence (GS 55) was as effective or more effective at increasing yield than application at full flag-leaf emergence (GS 39) or three applications of propiconazole (125 g ha −1) or mancozeb (1.6 kg ha −1) starting at stem elongation (GS 31). Application of propiconazole in either 154–2001 water ha −1 or 301 water ha −1 with 1% spray oil had similar effects. The response of two cultivars differing in resistance to S. nodorum and S. tritici varied, at least partly owing to the differing occurrence of the diseases at two locations. Resistance to only one Septoria species reduced, but did not prevent, yield losses because of occurrence of the other species. In the absence of combined resistance, fungicide sprays may offer a cost-effective means of reducing losses to S. tritici and S. nodorum in southern Western Australia when yield potentials are high and disease levels are moderate.