As neem is an oil I don't think much will get through the soil to the roots, most will be traped by the soil. As stated above neem is systemic so why use questionable methods to try to get the neem to the plant roots when spraying it does the best job ???
To get the best from neem you need to continue to use it for best results.
There is some really good information here on what you can do with neem and how and why you should use it often.
What is it? Neem Oil
Neem oil comes from the pressed seed of the neem tree – Azadiracta indica Juss – to be exact. It’s native to eastern India and Burma and has been used for medicinal purposes and pest control in India for thousands of years.
Claims are that the bark and leaves have quite a few anti’s covered.
- antiseptic
- antiviral
- anti-inflammatory
- antiulcer
- antifungal
…to name a few.
Is It Safe?
Well neem products are used in medication and consumed by humans. So any exposure to neem while treating your plants does not pose a threat. There are no restrictions put in place by the EPA.
I spoke to a few growers that have been using neem oil in their “pest control” program and they are delighted with it. Not just from the safety aspect… but the control. They have found the neem oil to be effective as a
repellant – insecticide – miticide and
fungicide. It also functions as an
antifeedant which discourages insects feeding patterns.
Insects would rather die than eat plants treated with neem oil.
Extracts from neem have shown incredible success with not only battling fungus problems but also many forms of root rot.
Why it Works
Extracts from the tree contain
azadirachtin, a relatively safe and effective naturally occurring insecticide. Let me preface the following comments by reminding you that the terms
"naturally occurring and/ or organic" do not universally mean safe. Pyrethrums, rotenone, and even the very dangerous nicotine are all organics that should be handled with great caution.
Where is it Used?
Neem extracts, on the other hand
are used in a wide variety of cosmetics, as a
topical treatment for minor wounds, to treat stomach ailments, as an insecticide in grain storage containers, and a whole host of other applications.
How Does it Work?
Neem works in many ways.
It is effective both as a topical and a systemic. It is
an antifeedant, an oviposition deterrent (anti-egg laying), a growth inhibitor, a mating disrupter, and a chemosterilizer. Azadirachtin closely mimics the hormone ecdysone which is necessary for reproduction in insects. When present, it takes the place of the real hormone and thus disrupts not only the feeding process, but the metamorphic transition as well.
It interferes with the formation of chitin (insect "skin") and
stops pupation in larvae, thus short-circuiting the insect life cycle. Tests have shown that azadirachtin is effective in some cases at concentrations as low as 1 ppm.
How to Use?
Neem oil or extract is most often used in an aqueous (water) suspension as a foliar spray or soil drench. Commonly, it is diluted to about a .05% solution. A drop or two of dish soap (not detergent) helps keep the oil emulsified. The mixture is then applied as a mist to all leaf surfaces and as a soil drench to the root system. It should not be applied as a foliar spray on hot days or in bright sun as leaf burn may occur.
Remember to agitate the container frequently as you apply and do not mix any more than you will use in one day. Neem breaks down rapidly in water and/ or sunlight.
What to Expect
Some users of insecticide need to be able to observe the instant results of their efforts in order to be convinced of the effectiveness of their choice. The application of neem derivatives does not provide this immediate gratification. There is virtually no knockdown (instant death) factor associated with its use. Insects ingesting neem usually take about 3 - 14 days to die.
Why Keep Using It?
Its greatest benefit; however, is in preventing the occurrence of future generations. It is also interesting to note that in studies it was found that when doses were given, purposefully insufficient to cause death or complete disruption of the metamorphic cycle, up to 30 surviving generations showed virtually no resistance/immunity to normal lethal doses.
I have been using neem oil as both a preventative and fixative and have had no insect problems.
It is said to be effective for mites, whitefly, aphids, thrips, fungus gnats, caterpillars, beetles, mealy bugs, leaf miners, g-moth, and others. It seems to be fairly specific in attacking insects with piercing or rasping mouth parts. Since these are the pests that feed on plant tissues, they are our main target species. Unless beneficial’s like lady bugs, certain wasps, spiders etc. come in direct contact with spray; it does little to diminish their numbers.
What about beneficial insects?
Not all bugs are bad. Some are beneficial to plants because they eat the insects that feast on your plants.
One of the many benefits of using neem oil insecticide is that it doesn't harm beneficial insects, such as lady bugs because they don't eat your plants. They'd rather make lunch out of aphids and other plant destroyers.
Of course, you don't want insects in your home. But if you move your plants outside for any length of time, you may expose your neem-treated plant to the good bugs. Don't worry -- they won't be harmed.
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SOURCES OF RELEVANT INFORMATION
Helson, B.V. 1992. Naturally derived insecticides: Prospects for forestry use. Forestry Chronicle 68: 349-354.
Helson, B.V.; Lyons, D.B. 1999 Chemical and biorational control of the pine false webworm. pp. 17-22 in D.B. Lyons, G.C. Jones and T.A. Scarr, eds. Proceedings of a Workshop on the Pine False Webworm.
CFS, Great Lakes Forestry Centre, Ontario Ministry of Natural Resources. Sault Ste. Marie, Ont. 49p.
Helson, B.V.; de Groot, P.; McFarlane, J.W.; Zylstra, B.; Scarr, T. 1998. Leader and systemic applications of neem EC formulations for control of white pine weevil (Coleoptera: Curcolionidae) on jack pine and white pine. Proc. Entomol. Soc. Ont. 129: 107-113
Helson, B.; Lyons, B.; de Groot, P. 1999. Evaluation of neem EC formulations containing azadirachtin for forest insect pest management in Canada. pp. 79-89 in RP
Singh, RC Saxena (Eds.), Azadirachta indica A. Juss. International. Neem Conference, Gatton, Australia, Feb. 1996. Oxford & IBH Publishing Co. PVT. Ltd. New Delhi.
Lyons, D.B.; Helson, B.V.; Jones, G.C.; McFarlane, J.W. 1998. Effectiveness of neem- and iflubenzuron-based insecticides for control of the pine false webworm, Acantholyda erythrocephala (Hymenoptera: Pamphiliidae). Proc. Entomol. Soc. Ont. 129: 115-126
Lyons, D.B.; Helson, B.V.; Jones, G.C.; McFarlane, J.W.; Scarr, T. 1996.
Systemic activity of neem seed extracts containing azadirachtin in pine foliage for control of the pine false webworm, Acantholyda
erythrocephala (Hymenoptera: Pamphiliidae). Proc. Entomol. Soc. Ont. 127: 45-55.
Wanner, K.W.; Helson, B.V.; Kostyk, B.C. 1997. Foliar and systemic applications of neem seed extract for control of spruce budworm, Choristoneura fumiferana (Clem.) (Lepidoptera:Tortricidae), infesting black and white spruce seed orchards. Can. Ent. 129: 645-655.
