Saturday, June 11, 2011

Making and using natural insecticides and fungicides for the garden

If you are a regular visitor to Tales from Toriello you will already know that we do not use chemicals in the garden and rely on natural control or potions that are derived from natural sources. Our climate here on the coast is a temperate climate that is humid and prone to sea mists. Conditions are such that our vegetables and plants are very susceptible to fungal infections such as mildew and blight, and infestations such as caterpillars, black fly and aphids.

With tomatoes, potatoes, courgette and marrow in full swing it is important for us to minimise the damage caused by fungal infections and reduce the infestations of caterpillars, aphids and black fly on plants around the garden.

The first thing to mention is that healthy plants, grown in fertile and well structured soil, in conditions that suit the individual plant will of course minimise any problems that may occur as will the use of companion planting  to encourage natural predation. We'll cover companion planting in a future post. Even the most efficient, experienced and knowledgeable gardener will succumb to the laws of nature from time to time so for us who are still serving our apprenticeships, infestations and plant diseases are all part of the valuable learning journey that we find ourselves on.

Natural Insecticides:

At the first sign of attack of aphids or black fly, we would normally spray the affected plants with a light soap and water mixture or garlic water made from macerated garlic and water, strained and then sprayed. This will need to be repeated in two or three days time but can be an effective control that is harmless to other wildlife. Rhubarb macerated in water for a few days also works well as a general insecticide.

Caterpillars are not that easy to get rid of and we have found that by far the most effective method is quick dispatch with gloved fingers. Birds in the garden can also help keep caterpillar populations under control especially if nesting nearby and feeding the voracious appetites of a young brood.

If your salad rocket is affected by Flea beetle they try using a spray made up from catnip soaked in water, it wont eradicate them but it will drive them away giving you a better looking crop during their short season.

Natural Fungicides:

Due to our humidity and climate we spray both prophylactically and symptomatically. Our main lines of defence come from two commonly occurring plants i.e. Rhubarb leaves and Horsetail plant. Both mixtures are made by the same method. In a large bucket or container, soak about 500 grams of bruised rhubarb leaves or bruised horsetail plant in a litre of water,  leave covered for about 5 days and stir occasionally. The liquid eventually stinks vile ( a bit like nettle juice if you are familiar with that). The liquid is then strained through a fine cloth and colander to prevent residues that might clog up the filter mechanism on the sprayer. Plants are sprayed, preferably on a dry day, with a good dose of the mixture and repeated as necessary.

This year we are trialling the horsetail mixture on the onion crop, marrows and cucumbers to prevent fungal infections and mildew.

We would love to hear from you if you have any other remedies or suggestions. Sometimes what works for one does not work for another and the experiences of others, trial and error is a great way of learning. Please get in touch or leave a comment if you have found that your own concoctions work for you.  

As with all potions, take care when handling both the raw plant and the liquid. Gloves and masks are should be worn to minimise inhalation or skin contact. If storing the liquids, keep out of reach of young children and pets.


  1. The only tip I have is to deal with caterpillars on brassicas BEFORE the eggs hatch. Rubbing away the eggs is much easier than tracking down all the hatched beasties and a less distasteful task. You do have to be vigilant though, and inspect the plants frequently during the egg-laying season.

  2. Anonymous6:50 pm

    Interesting tip for flea beetle on rocket - they plagued me this year. Although I also had problems stopping the rocket from bolting as soon as I turned my back! I've stopped growing normal tomatoes and now just grow cherry ones which don't seem to be so prone to mildew. Do you have success treating tomatoes with your fungal mix? I would love to be able to grow them and not just lose them all to the humid conditions!

  3. Our rocket self seeded and we seem to be having a never ending supply. As one lot bolts more comes. Tomatoes don't do well here at all. We have trialled 4 types this year and will report back on the trial soon. Fungicide helps to a point but we find protection, well-ventilated, the key. Still get problems though and guess we always will.

  4. Anonymous3:33 pm

    Lovely blog post! Lucky you for having horsetail, we've got none here. I didn't know about rhubarb leaves. We tried to control aphids with garlic and tobacco mixture. Previous 4 years I've always dipped the roots of young tomato plants in stingingnettle liquid before planting, last year I didn't and the crop was abysmal. But then again lots of people complained about bad tomato crop...
    Always find it hard to decide what works due to method, or pure luck (as in, some years there simply is less mildew etc)
    If only there was an effective method for dealing with the colorado beetle!

    1. Last time while collecting horsetail, we came across a beautiful stick insect.
      Thanks for the tip regarding the tomato plants, we will try it this coming week when we pot them up.
      I also question sometimes what dos and does not work but we rather continue using natural methods rather than resorting to the use of chemicals.
      Colorado beetle is not a problem for us and I am unaware of what may work. I tend to removed by hand those flightless pests big enough to catch and destroy wearing gloves.


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