Toil wrote:I just read through the thread, and thought there were some basic assumptions made by some, but not shared by others. So a little 101, beyond where it comes from.
Raw neem oil contains all the anti-feedant, growth regulating, and other sophisticated goodies. You are not going to see it at home depot. Google dyna-grow, and I think there is a brand called einstein oil. They are sold as "leaf polish".
The "neem oil" sold on most store shelves and labeled as an insecticide is basically just oil. It's neem oil minus the neem. It works! But so would mineral or vegetable oil.
There is also an extract that contains the "main ingredient" (I think you need them all together).
Please explain further: I have no idea how one could have "neem oil minus the neem." So far as I know, there is one compound from the neem tree currently available for sale to the general public as an insecticide. It may be marketed under different names, but it's all the same thing. I'm really stumped by "neem oil minus the neem." I buy cooking oil, which has never had neem in it; could this be what you're recommending in the recipe you provide?
The scientifically isolated "active ingredient" from the neem tree itself (Azadirachta indica
, one of two species in the genus) has been named, not surprisingly, azadirachtin
. This is what kills the insects and has those anti-feeding, growth-disrupting qualities that we employ to protect our plants.
This is how WikiPedia begins its article on azadirachtin
"Azadirachtin is a chemical compound belonging to the limonoids. It is a secondary metabolite present in the neem tree seeds. Azadirachtin is a highly oxidised tetranortriterpenoid which boasts a plethora of oxygen functionality, comprising an enol ether, acetal, hemiacetal, and tetra-substituted oxirane as well as a variety of carboxylic esters."
This natural chemical, used in traditional Indian medicine for thousands of years, wasn't synthesized until 2007. I think, from the above description, it's clear that azadirachtin is a very complex biochemical compound.
The article further states:
"It is now known to affect over 200 species of insect, by acting mainly as an antifeedant and growth disruptor, and as such it possesses considerable toxicity toward insects (LD50
): 15 Ã‚Âµg/g)."
refers to Spodoptera littoralis
, the Egyptian (or African) Cotton Leafworm, a major pest on vegetables, fruits, flowers, and other crops in Africa and Mediterranean Europe (this from an entomological abstract and WikiPedia both).
Therefore, the phrase "LD50
): 15 Ã‚Âµg/g" means that, when these insects were exposed to azadirachtin, it took only 15 micrograms of it per gram of body weight of the Leafworm to kill half of them. Thus, they were very susceptible to it.
However, in mammals--or at least in rats--the LD50
was >3,540 mg/kg, "making it practically non-toxic," according to WikiPedia. (Math and unit conversions not provided in this post.
Normal dilution rates for using neem/azadirachtin as a pesticide are 1 ounce of neem per gallon, or 7.8 mL per liter, of water.
The commercial product I purchased which contained neem oil (labeled as azadirachtin) was/is GreenLight's Rose Defense. I purchased it at a local, independently owned garden-supply store. I've also seen it at Pastime Ace Hardware near here. (I only go to HD as a last resort and have never been into a Lowe's.)
Basic info on Rose Defense is available at https://www.pestproducts.com/rose_defense.htm . Unfortunately, GreenLight seems to have changed the Rose Defense formulation since I purchased mine: the label on my container says 90% azadirachtin, not just 70%, as the current web page states.
Sunset Zone 17, USDA Zone 9