GrowER's Tips: What do you need to know about mould so it doesn't eat up all of your profit?

2021-11-23 11:16:41 GrowER

"Is it...? Is that MOULD?" I would get such questions in my inbox all the time while debating in hemp growers' groups. You're off for the weekend, your plants are fed, watered. You are on your way to some nice place. Unfortunately, we can't control everything. Power line surge, unexpected prolonged rainfall, weaker air circulation at the spot ... Imagine that weeks of hard work could be wasted by microscopic organisms.


Fungi can be divided into useful ones, (such as mycorrhizal), and those that nobody wants to see in their garden.

In this article, I'll show you how to deal with the latter.

Where did it come from at all?

There are 3 main stages in which mould infection occurs:

1. The vegetative phase. When our plants grow quickly, they create large, beautiful leaves, take up a lot of water and transpire quickly, releasing it into the environment. This creates high humidity in the room (or on the spot). Heat, humidity and insufficient air circulation are ideal conditions for mould growth.
Main problem: Insufficient air circulation.
Principal suspect: powdery mildew (fungi of the species Erysiphales).

2. Final weeks of the flowering phase. A few weeks after the flip, our plants have already developed beautiful flowers that are starting to swell. The larger and denser the buds, the greater the risk of infection.
Main problem: Moisture inside the big, beautiful cones.
Primary Suspects: At this stage, growers mainly struggle with fungi of the Botrytis cinerea species, also known as grey mould.

3. Drying / Curing process: It is very important that the air in the room can circulate freely during the drying stage. The source of air should never be aimed directly at the product.
Main problem: a badly prepared grower.

Therefore, to sum up, the main problem that causes mould is no or inadequate air circulation.

Okay, but what is it?

Unfortunately, there are several types of fungi and diseases they cause.

Grey mould - (Botrytis cinerea) [Bud ​​rot]

Grey mould most often develops in autumn (September-November) when the outside temperature drops. Botrytis c. loves humid and cool conditions. The most vulnerable to attack are the weak and healthy plants with large, hard buds. It was also noticed, that the nitrogen and potassium over-fertilization may increase the risk of grey mould.

Symptoms: grey, brown "bloom" and spots of the same colour on the stems, the inflorescences darken and begin to die, the same applies to the leaves, the affected leaf leaves the stem effortlessly.

Prevention: Maintaining adequate humidity (below 65%) and adequate airflow. Defoliation of fan leaves. Lollipopping. The use of bacteria sprays, e.g. Pseudomonas fluorescens, Bacillus subtilis, Lactobacillus Plantarum, Weissella paramesenteroides or Weissella confusa. [grace period of about 10 days], silicon supplementation

Combatting: If the plant was attacked at the late flowering stage, it is unfortunately necessary to cut off the infected parts and an additional 1 cm of the healthy part of the plant using garden scissors, for safety. The places where we have cut out the affected tissue should be sterilized with alcohol or hydrogen peroxide.

Downy mildew (Pseudoperonospora Cannabina, Leveillula Taurica) and true (Erysiphales, Sphaerptheca macularis)

Symptoms: Powdery mildew, as the name suggests, is characterized by a white coating on the upper leaves and on the stems or on the underside of the leaf, which looks like flour and can be easily rubbed off with a finger. It appears like most fungal diseases in periods of increased humidity.

Prevention: An additional dose of silicon and calcium to increase the strength of the cell wall, spraying with willow bark extract (salicylic acid), avoiding nitrogen overfertilization - increases the risk of its occurrence.


  • Bio: Neem oil spraying (with water and a few drops of soap), lecithin-based agents (e.g. Lecitec); spraying with 1 part milk and 9 parts water, removal of damaged parts of the plant.
  • Chem: spraying with copper-based preparations (downy mildew) and sulfur-based (powdery mildew - here it is very advisable to use a sulfurator), potassium bicarbonate, sodium bicarbonate (baking soda), removal of damaged parts of the plant

Root rot [Root rot] [Pythium] [Fusarium]

At first, I wasn't sure whether or not to include Pythium here, as it has been classified as Oomycetes (fungus-like parasites), but as it behaves similarly, it has been included.

Root rot is difficult to observe as basically the whole process takes place underground (growers who grow hydroponics have the advantage here). The plant gradually drinks less, its overall appearance deteriorates, the leaves look "drooped".

Prevention: Trichoderma viride - a useful fungus that inhibits the growth of many parasitic fungi; appropriate irrigation culture (do not overflow, water only when the pot is very light); maintain an appropriate pH of the substrate - fungi love acid soil, silicon supplementation.


  • Bio: Neem Oil, Potassium Bicarbonate, Sodium Bicarbonate (baking soda)
  • Chem: Watering with hydrogen peroxide solution (note - this solution kills all fungi and bacteria, both beneficial and parasitic).

Thank you for reading this article.

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