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Wednesday, July 22, 2020

My Neem Oil Recipe and How to Use it in Your Gardens: Always Use 100% Cold Pressed Neem Oil with Azadiractin

My Neem Oil Recipe and How to Use it in Your Gardens: 
Always Use 100% Cold Pressed Neem Oil with Azadiractin
By Gary Pilarchik

I have been using neem oil in my garden for nearly 10 years. It is organic and recognized as organic for your gardens. Before I talk about my recipe and how I use it... always test spray! This is the single most important thing you can do in your gardens, anytime you introduce a new spray. Spray impact varies, garden to garden, based on elevation, temperature, plant variety, ingredients (soap type), dosing and other factors. What might work in my garden, my damage leaves in your garden. Test spray each plant type. Spray some leaves and wait 48 hours.  If no damage is noted, spray your plants. I highly recommend using a garden journal and taking notes on the recipe, what you spray, when you spray and the outcome. It will help you manage pests and diseases in your gardens.

Make sure you DO NOT by 'clarified hydrophobic extract of neem'. It will be stated on the label. Why this can be sold as neem oil is beyond me. It is no better than using olive oil as it is refined and all the beneficial compounds, specifically azadiractin, are removed. Sure the product says 'miticide, insecticide and fungicide' but all oils do that. We call them a smothering oil spray as they coat and smother or suffocate soft bodied insects. Any oil does this. You want 100% cold pressed neem oil with all the natural compounds intact. The azadiractin is described below but it essentially coats the leaf, insect that chew the leaves digest it and it stops them from feeding. Typically they die off in a few days. That is the short version.

My Recipe for Neem Oil Spray

1-2 Tablespoons per gallon of water or
15-30 Millilitres per 4 litres of water

1 Tablespoon/15 millilitres of the pure Castile type soap per gallon/4 litres of water

Soap is needed to disperse the oil through the water when shaken. This disperses the oil evenly on plant leaves when sprayed. Without soap the oil would float. Shake the mixture every 30 second or so when spraying as the oil will settle back to the top. You can add a little more soap if needed, if the oil settles back to the top too quickly

1 Teaspoon/5 millilitres of other soaps per gallon/4 litres of water

Castile is pure soap with no detergents and that is why you can use more. That is the soap I recommend. If you are using other soaps that may contain degreasers, perfumes and other chemicals, start with 1 teaspoon and shake mixture. If the oil stays dispersed for a good 30 seconds, it is good to go. Many soaps are concentrates, so you want to start with a teaspoon. If needed, add a second teaspoon.

Soap type and quantity is the main cause of leaf damage.

I recommend starting with 1 tablespoon of neem oil for initial spraying. If needed increase it by 1 tablespoon. Insects will take several days to die but should stop feeding sooner.

When to Use Neem Oil Spray?

In general, neem oil lasts about 5 days on the plant leaf before the chemical compounds breakdown. You will realistically need to spray every 7-14 days depending on the insect and on the insect's life cycle. Eggs hatch at different rates and regular spraying will take care of newly hatched (caterpillars) or newly arrived insects (grasshoppers). The key to neem oil is that it has to be ingested. This works best for chewing insects like caterpillars.  Once sprayed and dried, it is reported it does little harm to pollinators. I have not noticed any issue with it. It is best to spray in the early morning or later evening for 2 reasons. You can spray around the pollinators and out of direct sunlight. 

I recommend keeping a garden journal to track when pests arrive. You want to start prevention spraying 2 weeks before they arrive and not when you notice chew holes. The later is fine, but you can prevent the damage. Preventative spraying, on a schedule, is best practice. 

Do not spray every plant variety in the garden. Very often, it is the brassica family of plants that are devastated by chewing caterpillars. Like kale, collards, cabbage, Brussels sprouts, broccoli and more. It can be used on other plants but only use it if there is a problem. Again, a journal helps you track issues from plant to plant.

What is Azadiractin?

Initially found to be active as a feeding inhibitor towards the desert locust (Schistocerca gregaria),[3] it is now known to affect over 200 species of insects, by acting mainly as an antifeedant and growth disruptor. It was recently found that azadirachitin possesses considerable toxicity towards African cotton leafworm (Spodoptera littoralis), which are resistant to a commonly used biological pesticide, Bacillus thuringiensis. Azadirachtin fulfills many of the criteria needed for a good insecticide. Azadirachtin is biodegradable (it degrades within 100 hours when exposed to light and water) and shows very low toxicity to mammals (the LD50 in rats is > 3,540 mg/kg making it practically non-toxic).

From https://en.wikipedia.org/wiki/Azadirachtin

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