The control of breakdown of potato seed pieces with fungicidal dusts

Abstract

The breakdown of potato planting material is a serious problem in southern Queensland, particularly where cut seedpieces are used. Some growers use captan (50 g kg-1) or zineb (40 to 200 g kg-1) dusts to reduce losses, but the values of these treatments have not been accurately assessed. A number of chemicals were compared with a standard zineb (80 g kg-1) treatment and no treatment under field conditions. While zineb significantly reduced breakdown in four of eight experiments, mancozeb at equivalent concentration was significantly better in three of four experiments. Mancozeb at 400 g kg-1 was significantly better again than the lower concentration. The 400 g kg-1 concentration of mancozeb was evaluated on three seed consignments for effect on plant stand and yield. The number of plants that emerged was increased by 29%, with a 34% increase in yield. The increase in yield over what could be expected from improved numbers of plants is attributed to the control of wilt diseases and prevention of early crop senescence, which followed the prevention of basal stem rot by retention of seedpieces.