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By Arlene


~ Following on a discussion as to whether Neem Oil can work on red lily beetles I found this info

Does neem oil insecticide work? Some gardeners question the usefulness of neem insecticide.

They sprayed neem oil, and did not see an immediate effect. They probably did not understand how neem oil affects insects.

Neem oil does work, but the way it works is different from other insecticides. Neem is not an instant, knock down, kill everything pesticide.

Neem oil affects insects in many different, ingenious and subtle ways.
How neem oil messes with the insects’ brains and bodies

Neem oil has many complex active ingredients. Rather than being simple poisons, those ingredients are similar to the hormones that insects produce. Insects take up the neem oil ingredients just like natural hormones.

Neem enters the system and blocks the real hormones from working properly. Insects “forget” to eat, to mate, or they stop laying eggs. Some forget that they can fly. If eggs are produced they don’t hatch, or the larvae don’t moult.

Obviously insects that are too confused to eat or breed will not survive. The population eventually plummets, and they disappear. The cycle is broken.

How precisely it works is difficult for scientists to find out. There are too many different active substances in neem oil, and every insect species reacts differently to neem insecticide.

Neem oil does not hurt beneficial insects. Only chewing and sucking insects are affected. It is certainly fascinating.

Like real hormones, neem oil insecticide works at very low concentrations, in the parts per million range. A little neem oil goes a long way.

But this is not something that happens over night. People spray neem oil as insecticide, and expect everything to die instantly, because that’s what they are used to from chemical poisons. When that does not happen they conclude neem insecticide does not work.

It does work! Give it time to work. It’s a much smarter way to deal with insect pests than to just kill everything.
How neem oil deters chewing and sucking insects

There is a nice story that demonstrates how grasshoppers react to neem oil insecticide. It goes something like this:

Someone did an experiment. It involved two jars, two leaves, and two grasshoppers. One leaf was sprayed with a chemical insecticide, and one with neem oil. The two grasshoppers were put in the two jars, with one leaf each.

The first grasshopper ate the leaf and died almost instantly. The grasshopper with the neem oil covered leaf did not touch the leaf and lived. At least for a few days. Eventually it starved to death.

What would you prefer? A poisonous half eaten lettuce, or an organic, untouched lettuce? It’s a no brainer, isn’t it?

Neem stops insects from eating the plants.

Part of this action is due to to the hormone like action of neem oil that I explained above. Insects “forget” to eat after they’ve been in contact with even traces of neem oil.

But it is also the presence, the mere hint of a smell of neem oil, that seems to be enough to keep leaf eating insects away. Neem oil can be very powerful as an anti-feedant and insect repellent.

This anti-feedant property is one of the most often advertised and lauded properties of neem oil insecticide. However, the hormonal effects I described above are even stronger.

Neem oil as an insect deterrent works well against grasshoppers and leafhoppers, but all other insect pests are controlled mostly through the hormone action.

The subtlety of the hormonal effects, and the fact that they may take days or weeks to manifest, makes people overlook them. Ill informed gardeners seek instant gratification, i.e. lots of dead insects immediately, rather than a balanced environment in the long run.

It’s a shame, because the hormonal effect is where the real power of neem oil lies. It’s the key to neem oil being an effective insecticide and good for the environment at the same time. It’s also important to understand this effect to use neem oil insecticide correctly.
Neem oil works from inside the plant

Many insecticides break down quickly. They wash away with rain, or when irrigating, or the sunlight destroys them. You either have to spray all the time, or you have to spray something that’s so stable that it stays around forever. That means the chemical builds up everywhere and eventually poisons everything, including you.

Neem oil breaks down very quickly, too. It is especially susceptible to UV light. But neem oil is also a systemic insecticide. That means you can pour it on the soil (not pure neem oil of course, you use a dilution or extract) and the plants absorb it. They take it up into their tissue, and it works from the inside. A leaf hopper may take a couple of bites, but that’s it.

However, this does not work for all insect species. The neem ingredients accumulate in the tissues deeper inside the plant. The phloem, the outermost layer, contains hardly any. A tiny aphid feeds from the phloem, it can not penetrate deep enough to get a dose of neem. But any leaf hoppers, grass hoppers or similar chomping insects will be incapacitated quickly.
People eat neem leaves to cleanse the blood, stimulate the liver, and boost the immune system. So we certainly don’t need to worry about a bit of neem inside our lettuce leaves. To me this is a much more attractive option than having poisonous foulicides build up in my garden.
Neem oil suffocates insects

Many gardeners use white oil (plain mineral oil) or even olive oil to combat soft bodied insects like aphids, thrips or whitefly. The oil coats the bugs and they suffocate. Neem oil insecticide does that as well. But it’s more like a little bonus on top of everything else it does.

It can be a hazard, though. Of course there is no difference between suffocating good or bad bugs. Oil suffocates anything. So this aspect can harm beneficial insects!
Neem oil and beneficial insects

Neem is non toxic for beneficial insects. The main reason is that insects need to ingest the neem oil to be affected, and beneficial insects don’t eat your plants. But you can still kill beneficial insects if you smother them with neem oil, so please be careful.

Beneficial insects are most active during the day. The best time to spray neem insecticide is very early in the morning, so the spray can dry before the good insects become active. Also a good time is the late afternoon or evening. Once the spray has dried it does not harm your bees, ladybugs, lacewings, predatory mites and wasps etc.
How can you make neem oil insecticide work for you?

Neem oil as an insecticide works in many different and complex ways, so you need to match your approach to the situation.

  • Should you make your own neem oil spray?
    Most garden centres these days carry some ready to use form of neem oil spray. Should you even bother to make your own?
  • Recipes for neem insect spray
    Recipes and instructions. Learn how to make your own neem insect spray

whilst this site is obviously trying to promote the use of their oil it does give some useful info such as normal dosage seems to be 2% ~ so will be trying that and also remembering to do it really late at night so that bees don’t get it on them.

Someone recommended this to me at a show to control rust on fuchsias but didn’t know what concentration to use, has anyone tried it?

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Fascinating Arlene, I will be trying this. I don't remember seeing it on the shelf before but will try my garden centre at the weekend. Thanks :-))

13 Apr, 2010


Thanks, Arlene for this info. :o)

13 Apr, 2010


Very informative Arlene....I have a bottle of Neem oil I brought back from India. Will give it a much better than chemicals.

13 Apr, 2010


Very interesting blog,Arlene,it certainly sounds effective...

13 Apr, 2010


recipe for insecticide below
Here is a recipe for a natural, safe, organic pesticide garden spray that is very simple to make. Neem oil comes from the Neem tree. Neem oil affects insects in ways similar to hormones. Insects have been reported to "forget" to eat after they've been in contact with even traces of neem oil. The smell of neem oil is also a deterrent.

Here is what you will need

>A clean plastic spray bottle

>100% Pure neem oil (do not get a blend, must be pure Neem oil, health food stores often carry it in the supplement aisle, make sure you select raw, cold pressed Neem oil, extracts do not have a high concentration of the insecticidal ingredient Azadirachtin and heat can also destroy this compound. If the oil does not say it was cold pressed, heat or solvents may have been used to extract the oil.
Insecticidal soap (preferred soap, this is just very pure soap made from animal fats, it is called insecticidal but it contains no pesticides or other chemicals, it can be purchased at garden supply stores or online, it is important to use only pure soap so you will not harm your plants)
Pure castile soap (this kind of soap is pure but is made from vegetable fats, it will work but the insecticidal soap is recommended over this kind, you can find castile soap at health food stores and even GNC’s)


Measuring devices (your bottle should have markings on the sides

Neem Oil Insect Spray Recipe
•5 ml neem oil (or about 1 teaspoon)
•12ml insecticidal soap or other detergent (or about 2 teaspoons)
•1 liter warm water

Always test a small area of your plants before spraying the entire plant. If the soap is too strong it can burn the leaves. Be aware that Neem oil has a strong pungent odor, you may want to be careful not to spray it on yourself of get it on your hands. It is not toxic to humans and is very safe. Some people though do want to have the odor on them. Neem oil make take a little time to work but it will have long lasting effects since it acts as a systemic insecticide. This means that the Neem will be absorbed by the plant and not just get washed off. The reason for using the soap is to quickly kill any existing pests that are presently on the plant and to help emulsify the water and Neem oil. The soap will wash off and does not become part of the plant. Since Neem is used a health supplement, there is no danger in ingesting it or having traces of it in your plants. Neem has long been considered to have many health benefits. Neem is non toxic for beneficial insects mainly because the beneficial insects are not the type that eat your plants. I have made this spray and used it in my garden with great results. I used it for aphid problems I had early in the season and I have not had a problem since.

13 Apr, 2010


Thanks Arlene, if you spray or water plants with it, will it be effective against slugs? and is it safe around pets?

13 Apr, 2010


It's safe around pets but not sure about the effect on slugs~

13 Apr, 2010


Thank you sounds very interesting will try it out

13 Apr, 2010


Thanks Arlene,

you have worked hard to produce all this info for us. I will certainly give it a try.

Are you going to the Cardiff RHS Show? Rachel and I hope to go on Friday.

I shall wear a GOY badge!

13 Apr, 2010


`will be there on Friday too ~ will be wearing a GOY badge too!

13 Apr, 2010


will jot this down arlene thanx for info ;o)

14 Apr, 2010


If you prepare neem oil with soap, you have to used it within 24 hours.
But you can buy ready made water soluble neem oil from companies like Nature Neem (
The forumulation is well tested and we can store for about 2 years. Whenever you required, you can just take 5 ml and mix it with 1 litre of water and spray over the plants.

I bought TOTAL CARE, a preserved neem oil in water soluble form using natural emulsifiers. You can buy directly from Nature Neem. More information about the advantages :

For buying the product :

Kind regards
Ashok from France.

18 Apr, 2010


WOW How interesting I hope neem oil does not mess with my brain, I use it in my cosmetics i e I make body cream with neem cocoa butter essential oil and coconut oil, better than asses milk!!

18 Apr, 2010

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