Treatment of seed potatoes with prochloraz for simultaneous control of silver scurf and black dot on progeny tubers

Summary Potato seed tubers infected withHelminthosporium solani andColletotrichum coccodes were treated with prochloraz (as Omega 450 g a.i. l⁻¹ EC) and/or prochloraz managanese chloride (as Octave 25 g/kg DP), and planted in two separate fields not previously cultivated with potatoes. Dipping seed 28 d prior to planting in 2,4 or 6 g a.i. l⁻¹ Omega, and dusting with 500 or 750 g Octave per 100 kg seed significantly reduced the incidence of silver scurf and black dot on progeny tubers. In one field, the higher concentrations of Omega and Octave gave slightly better control than the lower Omega concentrations. At the second site, postharvest application of 4 g a.i. l⁻¹ Omega or 750 g Octave per 100 kg seed limited development of both diseases on progeny tubers, with slightly better control when an additional Octave dusting was applied 14 d before planting. None of the prochloraz treatments adversely affected plant stand or tuber yield.