Pythium and Phytophthora
Phytium and Phytophthora are mostly fungal organisms found in the soil that can cause some plant diseases. Late blight and bulb rot are also counted among them. However, some Pythium species also have a positive influence on plants. Pythium and Phytophthora are often found in the ground and attack almost all plant species.
Pythium and Phytophthora attack the leaves and the root system of the plants and thus disrupt the absorption of water and nutrients considerably, so that the roots become brown and brittle and the plants wither from below. The most susceptible are small and young plants that have just emerged from the cannabis seeds, as they are less able to fight off attacks.
In cannabis, Pythium and Phytophthora usually appear as late blight and tuber blight (Phytophthora infestans). With this, brown spots form on the leaf edges or at their tips and the leaves gradually die off. These irregular spots make identifying the problem a lot easier.
The best active form of prevention is seed dressing, i.e. dressing the hemp seeds with fungicides, and treating the plants accordingly when transplanting, for example with the "good" Pythium oligandrum wood turner. The mycorrhizal fungus Trichoderma can also protect the plants from attacks by other types of fungus and even supports the development of cannabis.
If the roots are infested, you can only work with chemical agents, so it is best not to get that far in the first place. If only the leaves are infested, the best way to work is with copper-based contact fungicides, which should eliminate the fungus and only work on the surface of the plant without entering it.