Yo, what’s up my fellow growers? It’s your boy Dan and today we’re talking about a serious threat to our beloved cannabis crops: Fusarium. This deadly fungus can wipe out our entire harvest by clogging up the xylem and preventing our plants from getting the nutrients and water they need. But fear not, because I’ve got some tips to help prevent Fusarium from taking hold in our growing spaces.
First things first, let’s talk about what Fusarium is. It’s a type of filamentous fungus that lurks just below the surface of the soil and targets the root system. Certain species of Fusarium are harmless to plants, but one in particular – Fusarium oxysporum – is a huge threat to our cannabis crops. This pathogen can exist in the soil for years and if it makes contact with your cannabis roots, it will start colonizing your plants.
So, what does Fusarium do to our plants? It causes a condition known as Fusarium wilt, which means that it prevents our plants from uptaking the vital resources they need to survive. As a result, we get weak and wilting plants that struggle to survive, let alone produce a viable harvest. This fungus penetrates into the xylem and cuts off key nutrients like nitrogen and potassium, which are essential for photosynthesis. When this happens, our plants will rapidly wilt, topple over, and die.
But how can we spot a Fusarium infection? Look out for yellowing and wilting leaves, slowed or stunted growth, root and stem decay, reddish discolouration of the xylem vessel (visible only after dissecting the stem), orange, pink or white fungal growth on the outside of stems, swelling stems that may eventually split due to pressure, and a spread of decay and necrotic tissue up the stem.
Now for the bad news: there is no cure or valid treatment for Fusarium infections yet. That means prevention is our main line of defence. Here are some tips to minimise future occurrences:
1) Surrender infected ground: Once Fusarium settles into a patch of ground, it will remain there for years to come. You won’t be able to plant cannabis there for the next few seasons. Part of the prevention strategy involves not reusing ground where plants were previously infected.
2) Plant in pots: Growing cannabis in pots creates a semi-isolated environment. The growing medium of individual plants remains separate, which may help to prevent the spread of Fusarium from one root system to the next.
3) Destroy infected plants: Fusarium can continue to survive in infected plants. Burn any infected material in an isolated area of your garden and never add it to your compost pile. Wash any tools that have come into contact with the plant with a hydrogen peroxide solution.
4) Beneficial fungi: Inoculate your soil with mycorrhizal fungi. Not only do these beneficial microbes help plants absorb nutrients, but they might also lower the occurrence of other fungal pathogens.
5) Manage soil pH: Routinely test your soil pH. Fusarium prefers more acidic soil. If your numbers are off, neutralise the soil with dolomite lime.
Don’t let Fusarium wilt put you off growing cannabis outside! Many growers harvest their crops every year without ever facing this issue. Even if you never encounter Fusarium, it’s worth knowing what can be done to minimise its ideal conditions. Now go forth and grow on!