Influence of soil moisture and temperature on the survival of Pythium deliense causing yellowing of black pepper

Pythium deliense is a recently identified pathogen responsible for post monsoon yellowing of black pepper. The pathogen can cause yellowing and wilting and the affected vines show breaking of branches at the nodes and finally collar rot leading to death of the vines. To study the survival of P. deliense in soil, two kinds of experiments were conducted. One under laboratory conditions by artificially inoculating the soil at different temperatures and at a range of water holding capacity of the soil (moisture level 5%-100%) and the second under natural field conditions, for one year. The results showed that under laboratory conditions, the pathogen can survive for 23 weeks at a temperature range of 20 °C to 25 °C at 5% moisture level and for 22 weeks up to 35 °C at 50% moisture level. At 20 °C the pathogen can survive for 22 weeks at 25-100% of the field capacity. The pathogen can survive at field capacity level and at the temperature level of 25 to 35 °C for 21 weeks. Pathogen load in the field ranged from 4 to 16 in terms of Disease Potential Index (DPI) and decreased with the increase in the soil moisture level and showing positive correlation of 0.918 with percentage yellowing and pathogen load in the field soil.