TREATMENT OF SEED POTATOES WITH PROCHLORAZ FOR SIMULTANEOUS CONTROL OF SILVER SCURF AND BLACK DOT ON PROGENY TUBERS

Potato seed tubers infected with Helminthosporium solani and Colletotr ichum coccodes were treated with prochloraz (as Omega 450 g a.i. l(-1) EC) and/or prochloraz manganese 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 red uced the incidence of silver scurf and black dot on progeny tubers. In one field, the higher concentrations of Omega and Octave gave slightl y better control than the lower Omega concentrations. At the second si te, postharvest application of 4 g a.i. l(-1) Omega or 750 g Octave pe r 100 kg seed limited development of both diseases on progeny tubers, with slightly better control when an additional Octave dusting was app lied 14 d before planting. None of the prochloraz treatments adversely affected plant stand or tuber yield.