It has always confused me why some people (like myself) have excellent success using neem oil, either as a foliar spray or as a soil drench to deal with pests, and others don't. So there seems to be two types of neem oil: Pure cold pressed Neem Oil (PNO) and Hydrophobic Neem Oil (HNO). The former is 100% oil and the later 70% oil + 30% inert 'stuff'. The HNO has been through an alcohol extraction process to remove the azadirachtin (aza) from the cold pressed oil. The aza is the main active ingredient used to fight insects.
Now that the aza has been removed from the HNO leaving only trace elements behind, it can still be sold as neem oil. Whilst HNO can still be effective as a bug spray it relies more on the oil covering and suffocating the insects rather than the properties of the aza. So why do they remove the aza in the first place? Mainly to improve it's storage capabilities, 100% neem oil does have a shelf life, and to make it easier to use. There are even a couple of products out there where they add aza back into the HNO????
Personally I have found that the systemic properties of PNO basically work as an organic insect repellent for my plants. Bugs that used to frequent my plants for a feed like grasshoppers and caterpillars are now rare sights. I have watched Common Grass Yellow butterflies (CGYB) that usually love my flowering plants fly up to my girls and then fly away again. I have observed this not only on my plants but those of grow buddies who also use PNO as a soil drench. In the past there used to be numerous CGYB hanging around my plants laying eggs. These eggs hatch caterpillars that then used to crawl into my buds and start eating away, leaving me with dead and dying buds. The caterpillars also cause mould to infect my plants through the rotting dead buds or their crap.
Indoors using PNO systemically has helped me eradicate fungus gnats, spider mites and root aphids from my grow tent. The usual dose I use is 5ml/litre once a week or so and have used up to 12ml/litre to deal with a persistent RA problem. The PNO needs to be emulsified properly to be effectively dispersed into the water. It leaves no real residue on the soil or the roots when watered into the soil, but makes the leaves shiny almost waxy when sprayed. I only water by hand and don't think a PNO mix is suitable for reticulation systems. PNO when mixed with water it should be used pretty much straight away as it loses its effectiveness quite quickly.
Here are links that I have found helpful when coming to understand how neem oil/aza works.
http://www.ublcorp.com/files/Biological_Insecticides.pdf
http://www.neemfoundation.org/neem-articles/neem-in-organic-farming/agricultural-usepotential.html
http://www.discoverneem.com/neem-oil-insecticide.html
Here is a list of how aza affects insects:
Now that the aza has been removed from the HNO leaving only trace elements behind, it can still be sold as neem oil. Whilst HNO can still be effective as a bug spray it relies more on the oil covering and suffocating the insects rather than the properties of the aza. So why do they remove the aza in the first place? Mainly to improve it's storage capabilities, 100% neem oil does have a shelf life, and to make it easier to use. There are even a couple of products out there where they add aza back into the HNO????
Personally I have found that the systemic properties of PNO basically work as an organic insect repellent for my plants. Bugs that used to frequent my plants for a feed like grasshoppers and caterpillars are now rare sights. I have watched Common Grass Yellow butterflies (CGYB) that usually love my flowering plants fly up to my girls and then fly away again. I have observed this not only on my plants but those of grow buddies who also use PNO as a soil drench. In the past there used to be numerous CGYB hanging around my plants laying eggs. These eggs hatch caterpillars that then used to crawl into my buds and start eating away, leaving me with dead and dying buds. The caterpillars also cause mould to infect my plants through the rotting dead buds or their crap.
Indoors using PNO systemically has helped me eradicate fungus gnats, spider mites and root aphids from my grow tent. The usual dose I use is 5ml/litre once a week or so and have used up to 12ml/litre to deal with a persistent RA problem. The PNO needs to be emulsified properly to be effectively dispersed into the water. It leaves no real residue on the soil or the roots when watered into the soil, but makes the leaves shiny almost waxy when sprayed. I only water by hand and don't think a PNO mix is suitable for reticulation systems. PNO when mixed with water it should be used pretty much straight away as it loses its effectiveness quite quickly.
Here are links that I have found helpful when coming to understand how neem oil/aza works.
http://www.ublcorp.com/files/Biological_Insecticides.pdf
http://www.neemfoundation.org/neem-articles/neem-in-organic-farming/agricultural-usepotential.html
http://www.discoverneem.com/neem-oil-insecticide.html
Here is a list of how aza affects insects:
- Disrupting or inhibiting the development of eggs, larvae or pupae.
- Blocking the molting of larvae or nymphs
- Disrupting mating and sexual communication
- Repelling larvae and adults
- Deterring females from laying eggs
- Sterilizing adults
- Poisoning larvae and adults
- Deterring feeding
- Blocking the ability to "swallow" (that is, reducing the motility of the gut)
- Sending metamorphosis awry at various stages
- Inhibiting the formation of chitin
The emulsifier is blended in--you just add a ml or two to a liter and shake it up. Nice product for knocking critters out, but pricey compared to pure neem oil without the growth benefits.
