Influence of Soil pH and Moisture on the Biocontrol Potential of Trichoderma harzianum on Phytophthora capsici-black Pepper System

The role of abiotic factors in maintaining the population and proliferation of Trichoderma harzianum (Rifai) with respect to the survival and multiplication of Phytophthora capsici in black pepper system was studied in conducive soil under pot culture conditions. Trichoderma harzianum could grow profusely at a pH range of 4.0-5.0, while P. capsici could grow better at pH 5.5-6.0. Trichoderma harzianum survived and proliferated in soil at a pH range of 4.5-5.5 with 10-15% moisture level. P. capsici survived at a pH range of 4.5-7.0, but its multiplication was at higher pH levels (6.6-7.0) as indicated by the disease potential index and it was also found capable of surviving at all moisture levels tested. When Phytophthora infested soil was supplemented with Trichoderma, a disease reduction of 27.5-63.75% was noticed in 20 days application compared to soil without Trichoderma supplement. Hence for the biological control of P. capsici in black pepper system, the pH of the soil has to be maintained after at 4.5-6.0 in order to facilitate the growth and proliferation of Trichoderma which in turn will reduce the population of Phytophthora.