Make simple food-garden pest control sprays at home, so you avoid the nasty chemicals that are present in many commercial products. These 'old as the road' recipes cost very little and have been effectively used by generations of food gardeners, without putting anything that is too poisonous to humans on your produce or in your soil.
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| Scale on a lemon tree |
Below you will find sprays for the following pests and diseases:
A few thoughts before you spray ....
Keep spray ingredients and mixtures secure, labelled, and out of reach of children. If you have small children in your household, please do not use soft drink bottles for spray mixes, as this might tempt them to drink the content!
Most of us don't want to use poisons in our food garden if we can help it. Spraying a pesticide is therefore something we only do if other pest management steps failed or don't apply. These steps are:
- Make your food garden as healthy as possible
- Don’t please your pests
- Keep them out
- Catch and remove
- Is further action needed?
- Use a low-impact pesticide (like the ones mentioned in this blog post)
Each of these steps is discussed in the Safe Pest Control series on this blog. It starts with Safe Pest Control - Step 1 and 2 here.
Some of the pesticides discussed below are broad-spectrum. This means that they will affect a wide range of insects. That can include beneficial insects such as pollinators (bees etc.) and predators (ladybirds etc.) that help you to get rid of your garden pest. For every pest control spray below it will be mentioned whether they are broad-spectrum or not.
Gloves, face protection and other protective clothing should be worn by anyone with a sensitive skin or allergy, both during mixing and spraying.
Spray when there is little or no wind as spraying during windy conditions will cause spray-drift. It may hit plants you did not intend to spray and spray may hit you.
Most of the pesticides described below should be repeated after rain.
Always wash produce before consumption.
It would be great to hear from you if you use a homemade pest control spray that is not mentioned below and that is effective in Tasmanian conditions. Please email Max at foodgardengroup@gmail.com
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Baking Soda
Is effective against?
Baking soda spray is effective against fungi like Powdery Mildew, Rust, Early Blight and Black Spot. It can be used as a preventative spray or to kill these fungi when already present because it lowers the pH on the surface of leaves to a level that makes it hard for the fungi to survive. There is no evidence that it kills insects.
How do you make it?
To one litre of water add:
- ½ teaspoon of vegetable oil
- a drop of dish washing liquid
- 2 teaspoons of bicarbonate of soda
Baking soda, sodium bicarbonate and bicarbonate soda are all names for the same product. It is not organic, but used in small quantities it is completely harmless.
How should you use it?
Don't use more than once per fortnight as plants won't like the lower pH if applied more often. Wash produce before consumption. Use baking soda spray if milk spray (discussed below) does not deal with the problem.
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Baking Soda & Sugar
Is effective against?
This spray is effective against ants. Ants are not normally a threat to food garden produce, but ants protect Scale against predators, and therefore getting rid of ants can help you get rid of Scale on fruit producing bushes and trees.
Ants will be attracted to the sugar in the mixture described below, eat some of it, and collect more to take home to feed others, so all of them will get their share. With the sugar the ants will ingest the baking soda in the recipe described below and die.
How do you make it?
Combine the following ingredients in a bottle or jar with a lid, and then shake:
- 5 tbsps of baking soda (sodium carbonate),
- 5 tbsps of icing sugar (powdered sugar ; don't use coarse sugar)
- 3 tbsps of water
How should you use it?
Place small amounts of the mix where you see the ants, and where you won't step on it.
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Bordeaux Mix
Is effective against?
This fungicidal spray was a long time ago invented in the Bordeaux region of France to control Mildew on grape vines. It can also be used to control Curly Leaf on peach and nectarine trees, Brown Rot on stonefruit, and Rust on raspberry leaves. This is a fungicide that kills several varieties of fungi. Bordeaux Mix is toxic to bees.
The best time of day to use Bordeaux Mix is late afternoon/early evening, as bees will be returning home at that time of day, and the spray is likely to be dry by the next morning (thank you, beekeepers Laura and Frank, for this advice).
How do you make it?
Don't use a metal bucket. To half a bucket of water add:
- 100 grams of copper hydroxide (available at nurseries)
- 100 grams of hydrated lime ('builders lime')
Never use Bordeaux Mix on plants when in leaf, as foliage burn can occur.
Use it after leaves have dropped in late autumn or early winter and again just before new leaves appear in late winter or early spring.
Completely cover bare branches of peach or nectarine trees, or grapes, or the canes of raspberry bushes.
Bordeaux mixture colours the sprayed plants blue. The spray can withstand light rain.
The mixture tends to settle quickly, so it must be constantly agitated during spraying.
The lime content can block the fine nozzles of sprayers.
The mix is most effective when freshly mixed, so use immediately, or within a couple of days.
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Burgundy Mix
Is effective against?
Burgundy Mix is used for the same purposes as Bordeaux Mix, but the lime is replaced by soda. It is used to control Mildew on grape vines. It can also be used to control Curly Leaf on peach and nectarine trees, Brown Rot on stonefruit, and Rust on raspberry leaves. This is a fungicide that kills several varieties of fungi.
Burgundy Mix is toxic to bees. The best time of day to use Burgundy Mix is late afternoon/early evening, as bees will be returning home at that time of day, and the spray is likely to be dry by the next morning.
How do you make it?
Don't use a metal bucket. To half a bucket of water add:
Don't use a metal bucket. To half a bucket of water add:
- 100 grams of copper hydroxide (available at nurseries)
- 100 grams of washing soda (available at supermarkets as a water softener)
Burgundy Mix is used in the same way as Bordeaux Mix, except that you won't have the agitate the mix constantly, and there is less chance that your spray nozzle will clog up.
Never use Burgundy Mix on plants when in leaf, as foliage burn can occur.
Use it after leaves have dropped in late autumn or early winter and again just before new leaves appear in late winter or early spring.
Completely cover bare branches of peach or nectarine trees, or grapes, or the canes of raspberry bushes.
Burgundy Mix colours the sprayed plants blue. The spray can withstand light rain.
The mix is most effective when freshly mixed, so use immediately, or within a couple of days.
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Garlic Spray and Chilli Spray
Is effective against?
Garlic Spray and Chilli Spray kill aphids, caterpillars, slugs, snails, other soft-bodied insects. It also kills Powdery Mildew and Downy Mildew. It is broad-spectrum.
Strong garlic can kill them outright. Garlic spray also has anti-fungal and anti-bacterial properties. The smell may mask the smell of the insect’s preferred host plants, so it can also protect plants that way.
Garlic and Chilli Sprays will be effective for between 24 and 72 hours, depending on temperature, moisture and amount of direct sunlight.
How do you make it?
- Finely chop four good-size garlic cloves
- Mix well with one tablespoon of light vegetable oil and two cups of water
- Leave to soak for 24 hours
- Strain the liquid into a spray bottle, using a funnel and strainer
- Add one teaspoon of liquid soap, and once more mix well
- Clearly label the spray bottle
There are variations of this type of spray that use warm water instead of oil and/or add onions and/or hot chillies (chilli spray).
How should you use it?
Some plants have very sensitive leaves, others don't. Test the intensity of the spray by spraying it on one leaf of the plant(s) you want to spray. If 24 hours later that leaf seems affected, dilute the mix with more water.🐛
Horticultural Oil
Horticultural Oil is also known as White Oil. See White Oil below.
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Insecticidal Soap
Is effective against?
How do you make it?
Whereas horticultural oil is a mixture of oil and soap, Insecticidal Soap is a mixture of water and soap made as follows:
Insecticidal soap is effective against soft-bodied insects such as aphids, some scales, whiteflies, mealybugs and thrips. It is broad-spectrum, but hard-bodied insects, such as bees and wasps, are not harmed.
How do you make it?
Whereas horticultural oil is a mixture of oil and soap, Insecticidal Soap is a mixture of water and soap made as follows:
- Use a soap that is environmentally friendly.
- Combine in a hand sprayer 1 tablespoon of soap flakes to 500 ml of water.
- Put the spray top on and shake well until the soap is completely dissolved.
Here is my own even simpler recipe:
- Pour a bit of dish-washing liquid in a hand sprayer
- Add water, put the spray top on and shake.
More info about this spray can for instance be found here.
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Milk spray
Is effective against?Milk spray is quite effective in killing Powdery Mildew and Downy Mildew by creating an antiseptic effect when exposed to sunlight. It kills nothing else.
How do you make it?
- Combine water and full cream milk in the ratio 9:1
- Shake well
- Don't make more than you need on the day as left-overs won't keep
How should you use it?
The spray needs to be applied during daylight. It won't work if applied at night. It might be best to apply it early in the morning so leaves don't stay wet too long. Do not keep left-over milk spray for later use. It will go off and no longer be effective. Use baking soda spray (discussed above) if milk spray does not do the job.
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Rhubarb Brew
Is effective against?
Rhubarb leaves contain oxalic acid that is toxic to humans. It makes a great natural pesticide that is effective against leaf-eating insects such as aphids. This is broad-spectrum.
How do you make it?
Wear gloves, face protection and other protective clothing while making Rhubarb Brew. It is made as follows:
- Add to a pan four cups of water for every two cups of finely-cut rhubarb leaves
- Boil this for half an hour
- Allow to cool down, then strain
- Mix in 20ml of dishwashing liquid
- Put it in a bottle marked Rhubarb Brew - Poison
How should you use it?
Rhubarb Brew will be most effective if you use it immediately. If that is not possible, use it within a day or two. The longer you keep it the less effective it will be. Spray both sides of the leaves of affected plants. Focus on covering the leaves, not the pest. They will eat the leaves and die. Do not spray plants from which you intend to eat produce in the next few days. Always wash harvested produce before consumption.
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White Oil
Is effective against?
White Oil kills aphids, moths, scale, whiteflies, leaf miners, mealy bugs and thrips. It is broad-spectrum.
How do you make it?
- Use a dishwashing liquid that is environmentally friendly.
- Combine in a jar with a lid 1 cup of thin vegetable oil + ¼ cup dishwashing liquid.
- Put the lid on and shake well.
- Mark the jar ‘White Oil’ + expiry date = [today' date + 3 months].
- Store somewhere cool.
- The vegetable oil might go off after a while, so discard this concentrated mix after 3 months.
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| My bottle of 'white oil' |
The photo above shows a bottle of concentrated While Oil that I made (before I put a label on it). Don't be concerned if it is not actually white. It is only white if the dishwashing liquid you used is white.
How should you use it?
- Don’t use it on hairy or soft leaved plants like lettuce, because it is likely to burn the leaves.
- Don't use it in temperatures over 30 degrees Celsius because it may burn leaves.
- Preferrably spray early in the morning when temperatures are lower.
- In a spray bottle mix 1 dessert spoon of the concentrated mix with ½ litre of warm (not hot) water.
- Shake well. With the mix I made (photo above) the content of the spray bottle was actually white, but the colour of the mix is irrelevant.
- Thorough coverage of insects at the time of spraying is essential, so focus on areas on plants and in the air where there are whiteflies. Spraying of plants that have no whiteflies on them will only help if a whitefly lands on the plant while it is wet.
- Do this once a week for at least three weeks.
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