Potato crop (Solanum tuberosum L.) is one of the most important vegetable crops in Egypt. Integrated treatments between humic acid at concentrations 6.0 or 8.0 ml/L followed by sulfur at 3.0 or 4.0 g/L were evaluated against early blight disease under sever field infection. All tested concentrations of humic acid had no inhibitory effect on Alternaria solani. Meanwhile, sulfur at concentrations 3.0 and 4.0 g/L caused complete reduction of linear growth of A. solani under laboratory conditions. In greenhouse experiments, results indicate that the integrated treatments between humic acid followed by sulfur treatments with all tested concentrations reduced early blight severity more than 85.7%. The highest increase in chitinase activity was obtained with humic acid at concentrations 6.0 and 8.0 ml/L when applied either alone or integrated with sulfur treatments which increased the chitinase activity more than 120.0%. In field experiments results indicate that the most effective treatments were integrated treatments between humic acid followed by sulfur with all tested concentrations which reduced the early blight severity more than 83.6%. Potato plants treated with sulfur at concentrations 3.0 or 4.0 g/L or Redomil - plus 2g/L resulted in reducing early blight severity more than 66.7% during two succession growing seasons. Marked increase in potato yield was obtained with integrated treatments between humic acid followed by sulfur with all tested concentrations which increased the potato yield more than 59.3% during the two growing seasons. It could be suggested that integrated treatment between humic acid followed by sulfur might be used commercially for controlling early blight disease of potato plants under field conditions. |
