Fungi in Plants: How to Prevent and Eliminate. Types of Natural Fungicides

The fungi of the garden are a very common problem. Let’s see some tips and techniques to prevent them, and possible ecological treatments to eliminate fungi if they appear.

How to prevent garden fungi?

Preventing fungi is the first thing to do to fight infection. It is not the same to try to eliminate a plague of insects that we can see with the naked eye and, many times, eliminate manually, than to kill microscopic beings such as fungi.

The main objective should be to ensure that the plants in the garden do not get sick  . It seems obvious but many times we do not give the importance it deserves to the prevention of fungi and other diseases.

Measures to prevent garden fungi

But … How to prevent fungi in plants? It is important to combine tasks to keep the soil and plants healthy and free of pathogens.

Some of the measures to  prevent garden fungi are the following:

  • Maintain a healthy and fertile substrate,  incorporating natural fertilizers such as worm castings, compost and other organic fertilizers made with plants, such as green manures.
  • Water the soil with bioestimulantes and fortifying prepared as preparations algae, nettle or horsetail further enriches the soil and provides “defenses” to plants that are more resistant to fungal infections on leaves and other pathogens.
  • Plan crop rotation. It is one of the basic practices of organic farming due to the benefits it brings, including preventing the proliferation of diseases. It consists of making several groups of plants similar or related to each other and growing each one in a different area or container, exchanging places each year (more information in the post on Rotating crops in the garden) .
  • Promote aeration avoiding a high density of plants so that humidity does not favor the appearance of fungi (the plants should not be too close together, and if this is the case and it is necessary, you will have to thin them).
  • Properly manage irrigation and drainage : do not apply excessive watering and do it preferably in the morning (so that the plants dry throughout the day), so that the humidity of the environment does not increase too much.
  • To save water or prevent fungus leaves the recommended drip irrigation systems such as drip irrigation , compared to others like spraying.
  • Use disease resistant plants, such as landraces , or some varieties resistant to mildew or rust.
  • Release into the soil products with populations of competing fungi or natural enemies of the main causes of diseases (mildew, powdery mildew, botrytis …). Two examples are natural antifungals with Trichoderma and Bacillus fungi , which have been shown to be effective in the fight against Mildew, Botrytis or Fusarium, among others.
  • Place organic mulching or mulching at the base of the crops to help maintain humidity and reduce the incidence of weeds that can spread fungal diseases and other infections.

In the post «How to take care of the garden soil. Fertilizers and work to improve the soil » there are more details on the steps to improve the soil and thus prevent fungi in plants.

Natural Fungicides: Plants to fight against fungi

There are three plants to make homemade preparations that are very effective in fighting garden fungi: horsetail, garlic, and nettle.

Horsetail ( Equisetum arvense )

It is one of the most effective plants to make natural preparations that keep the garden healthy. Homemade horsetail fungicides can be applied to prevent fungus on plants , once they have appeared, to weaken the disease.

By regularly applying horsetail to the soil we get it to be more protected and we have less chance of fungi passing to our plants.

Nettle against fungi

This plant reinforces the vigor and health of the crops. Nettle-based preparations, like other phytofortifying products or agricultural biostimulants help prevent and eliminate fungi from plants.

Nettle is more effective than horsetail for fungi that normally develop at low humidity, such as powdery mildew.


Garlic has components, such as allicin or ajoene, which are powerful bactericides and fungicides, so homemade preparations with garlic will help prevent and treat diseases and diseases caused by fungi and bacteria. It is also effective in driving away pests such as worms, aphids, and mites.

Homemade fungicides for garden mushrooms

  • Horsetail slurry:  Boil approximately 1 kg of fresh horsetail (500 grams if dry), in 10 liters of water for half an hour. Then filter it and let it rest to macerate for a few days, until an unpleasant smell appears. Strain the mixture to remove the plants and dilute 1:10, that is, adding 100 liters of water for every 10 liters of horsetail macerate (Maximum storage: 2 weeks).
  • Horsetail decoction : boil 100 grams of fresh horsetail (or 50 grams if it is dry) in 5 liters of water for one hour. Let the decoction stand, strain and let cool. Use diluted 1: 5 or 20% (five liters of water for each liter of decoction).
  • Nettle slurry: 1 kg of fresh nettles (or 250 grams of dried nettles) + 10 liters of water. Leave to marinate for about 10 days and stir it every two or three. Once this time has passed, remove the film that has formed on the surface of the liquid and you can filter it and store it in jars to use when you need it. When you are going to spray it on the ground or crops, you must dilute it in water (in a 1:20 ratio). If you don’t have time or place to make this preparation, you can buy the extract directly.
  • Garlic infusion : marinate 6-8 peeled and minced garlic cloves in one liter of water for 24 hours. Then boil the water with the garlic for 20 minutes over low heat, strain and allow to cool.

How to apply natural fungicides for fungi on plants

If you have observed that there are some areas where your plants have been attacked by pests or diseases, it will be very important that you carry out treatments to prevent fungi  in those areas.

Another option that will help the plants grow healthier and more vigorous is to apply a mixture of horsetail decoction with nettle slurry.

In autumn and winter (when we have not yet planted anything) periodically treat the soil with one of the ecological fungicides that we have seen by spraying it on it. It is advisable to use about 30-40 liters per hectare (In a garden of 20 square meters for example, it would be equivalent to spraying 60-80 ml of the preparation).

Before sowing or just sowing, disinfect the seedbeds and the substrate by spraying the slurry against fungi, or  mixing the slurry with an infusion of tansy (a plant that is also used to make ecological remedies against fungi).

Before or after cultivation tasks such as transplantation, pruning or pruning, it  is advisable to spray the plants (highly recommended to prevent tomato fungi).

During cultivation, spray some of the natural fungicides every 10-15 days on the crops (especially those that are more sensitive to fungal attacks).

If fungi appear on the plants in the garden, act as soon as possible. As soon as the first symptoms of a fungal disease are seen, the plants must be sprayed with the natural fungicide as frequently as necessary and for the entire duration of the cultivation (The ideal during the first days is to treat 4-8 days in a row, until the fungal infection subsides a little).

Other preparations to fight against fungi in the garden

Baking soda, potash soap, powdered sulfur, Bordeaux mixture, chamomile infusion or onion infusion are other ecological fungicides that can be used in the garden to eliminate fungi from plants.

In this other article on organic homemade fungicides against fungi in the garden you can find other natural preparations that can be used in the garden to eliminate fungi from plants.

If you know other ecological remedies and treatments against fungi or have experience using these preparations in the organic garden, you can leave your contributions or doubts in the comment thread below.

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