Coltivazione cannabis

Fungi that affect cannabis: causes and remedies

Mushrooms are silent presences that can ruin months of work in the blink of an eye. They are patient beings, a latent presence that lives crouched around your plants, waiting for conditions to become favorable for their spread. Humidity and mess are mushrooms' best friends: they show up without knocking and, if not discovered in time, can destroy an entire crop.

The first step to avoid this annoying presence is prevention, so you need to pay attention to the hygiene of your cultivation space. If you grow indoors, it is essential to disinfect everything that comes into contact with the plants, starting from the growbox up to pots and utensils . To do this you can use fungicidal products or a solution of water and 5% bleach . During cultivation, however, it is very important to keep the area clear and clean; some professional growers even wear clean clothes before entering the grow space, to avoid bringing in spores from outside .

If you grow outdoors it is much more difficult to keep this aspect under control, but using disinfected utensils can still be very useful. You must also pay close attention to organic remains , which could turn into a receptacle for spores ready to devour your cultivation.

Other aspects to keep under control are temperature and humidity levels : to develop, fungi need certain environmental conditions , which are essentially heat, humidity and lack of ventilation . If you check that your cultivation is adequately ventilated, the relative humidity does not exceed 50% in the flowering phase and the temperature is not higher than 25 degrees, you are already well underway. Outdoors it is almost impossible to monitor these factors 100%, so it is important not to excessively prolong cultivation times and above all to avoid harvesting in autumn, when the risk of rain becomes much more present.

Use preventative products: they don't need to be chemical, there are an infinite number of organic substances with effective fungicidal action. If cuttings coming from outside are used, it is very important to check that the original mother is healthy: there is no point in thoroughly cleaning the cultivation space if the infection is already inside the cuttings.

What are the most dangerous molds?

  • Botrytis cinerea is a fungus of the Sclerotiniaceae family, and attacks many varieties of plants, including cannabis and vines. The Latin name “cinerea” refers to the ash gray color taken on in particular by grapes when attacked by this species.

When Botrytis attacks the marijuana plant it tends to initially attack the base of the plant's stems, making its identification rather complicated. Usually the first visible signs can be seen on the smaller leaves , especially those around the buds, which tend to wither, discolor and dehydrate . You can also notice a whitish fuzz inside the buds and on the stems of the leaves near the flowers. It usually takes on greyish, blue-green or white colors.

When the humidity is too low, Botrytis could cause dehydration of part or all of the bud , which will tend to crumble to the touch; when the humidity is high it can instead envelop the flowers, leading them to decompose and take on a mushy consistency.

If identified at an early stage it will be possible to stop its advance. If, however, Botrytis is identified in an already advanced stage, the plant will most likely be covered in small circular black formations distributed on the surface of the mold. These are Botrytis spores, which are just waiting to spread throughout your cultivation at the first breath of wind.

  • Powdery mildew , also called white mite, fog or albugo , is a trophic plant disease caused by Ascomycota fungi in the asexual phase of the cycle, previously identified with the genus of imperfect fungi Oidium.

It appears as a thin layer of powdery, whitish mold that accumulates on the surface of the leaves of Cannabis plants, which are attacked first, before the "white disease" spreads to the entire plant. Powdery mildew inhibits photosynthesis, blocking the Cannabis plant's energy sources and, consequently, leading to its death.

The leaves curl up, turn yellow, take on brown colors and finally die. Although it is difficult to detect in its early stages of development, powdery mildew tends to appear on infected leaves in the form of small, raised circular spots. Like Botrytis, powdery mildew also develops small black spores, visible in its most advanced stage, which spread easily even in indoor crops.

Both of these types of mold can develop both indoors and outdoors and can infect a large number of Cannabis plants in a short time; this is why they are extremely dangerous even on a single specimen, it is easy for them to spread quickly throughout the entire plantation. Fortunately, these molds tend to appear and develop only in certain circumstances, which must be followed by some specific conditions before they can spread to an entire plant.

What are the causes?

For Botrytis or powdery mildew to be able to attack a plant, three specific conditions must exist: temperature changes, stagnant air and excessive humidity/water . The best way to

preventing the attack of these molds is therefore to ensure that none of these parameters occur within a plantation and, at least, they must be prevented from coexisting in the same phase.

The threat of mold is always lurking, but increases as we approach the maturation of the flowers , which progressively swell, hindering intra-floral ventilation. Often large buds expose the plant to greater risks related to mold; many growers prefer to act with the so-called "apex pruning" in order to reduce the size of the upper buds. You will get smaller flowers , it's true, but they will be more numerous and above all healthier and safer . The small size of the buds reduces the amount of humidity and consequently the risk of falling victim to mold.

Some remedies

To combat Botrytis the only option is to use organic sprays , such as products based on Bacillus subtilis (Serenade), which can help treat Botrytis and keep it under control until harvest , but will never succeed in eliminate it completely. To prevent the spread of mold, you can move infected plants to a warm room with extremely low humidity.

Against powdery mildew, however, some additional strategies can be adopted. There are some natural remedies that seem to work: you can add two teaspoons of apple cider vinegar in 1L of water and spray the solution on your plants, or you can prepare a mixture with 60% milk and 40% water to always spray on plants. Both of these formulas have the potential to kill powdery mildew, but their actual effectiveness is questionable.

Beyond natural remedies, the first thing to do is to eliminate all infected leaves and move the plant to a warm area with low humidity; then you can proceed to apply a safe and specific fungicide spray to treat mold infections. This should go some way to keeping the spread of powdery mildew under control.

However, it is important to keep in mind that any fungicide-based treatment will irremediably compromise the final quality of the buds. These products, in fact, tend to alter the flavours, aromas and quality of the flowers themselves. Furthermore, don't forget that you will be smoking the buds yourself, so always carefully evaluate whether it is really worth inhaling fungicides and molds too.

Leave a comment

Please note, comments need to be approved before they are published.

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.