Efficacy Evaluation Of Fungicide Programmes For The Control Of Late Blight In Potatoes.

Abstract

Field experiments were conducted between 1989 and 1992 to compare the efficacy of different fungicide programmes to control late blight of potatoes. The protectant fungicide Shirlan, the translaminar fungicide Acrobat and the systemic fungicide Ridomil MZ followed by Dithane were compared with the protectant fungicide Dithane and an unsprayed control treatment.

The longest delay in disease incidence was recorded following the use of Ridomil MZ and this together with Shirlan were significantly better than the Dithane control. All test treatments resulted in better foliage blight control compared with the Dithane control treatment. The lowest level of foliage blight at the end of the growing season was recorded following the Shirlan treatment, but this was not significantly better than Ridomil MZ or Acrobat treatments.

All three test fungicides significantly reduced the level of tuber blight compared with untreated control. While all test fungicides gave better control of tuber blight than Dithane, these differences were only significant in some years. The three test chemicals all resulted in equivalent marketable yields when compared with the Dithane control. This would indicate that there were no phytotoxic effects from any of the test chemicals.