Tomato (Lycopersicon esculentum Mill.) as one of the vegetable commodities whose production is not always stable because there are various obstacles in the environment, both fast-changing weather and pests and diseases (Trisnawati & Setiawan, 2001). To achieve steady production with sustainable environmental conditions, it is necessary to carry out biological control while maintaining harmony, harmony and environmental balance. application Trichoderma sp. on the soil is the right way to increase plant growth, besides this method is effective in controlling diseases caused by soil-borne pathogens. The purpose of this study was to determine the interaction of soaking duration and the best application time to suppress the development of wilt disease in tomato seedlings. This research was conducted in Cempaka Banjarbaru, South Kalimantan. This research was carried out for approximately 3 months, namely from January - March 2020. The study was carried out using a Randomized Group Design from two different treatments, namely the variation of immersion using Trichoderma sp and the time of application of Trichoderma. The result of this study is that (1) the best soaking duration is to use the length of soaking Trichoderma sp. For 10 minutes it has been able to suppress plant wilt disease, (2) the application time of Trichoderma sp needed to suppress the development of wilt disease in tomato seedlings at T0, namely the application time without using the Trichoderma sp application and (3) the treatment of soaking variations with the time of application interacting in an influence on the suppression of the percentage of disease both on observations of 2,4,6 and 8 MST. Tomato seed plants are able to suppress the percentage of wilt disease of tomato plants in the treatment with Soaking Trichoderma P1T0, which is for 5 minutes with an application of 0 grams / plant, namely with an average value of 1.92.