I believe that the insecticidal properties of neem are derived from the oils extracted from the seeds. At least, neem oil is the only product that I have seen for that purpose.

In its native India the tree parts used are the bark, seeds, leaves, as well as the roots for various things. The only way for you to know for sure is to try making a spray or what ever from those leaves and see what it does.

Thanks rhizo_1 and kimmsr.

I will try to blend up some of the pieces. Does anyone know if too much may damage a rose, will it burn the leaves?

Joy

I am not sure they will, you are right about the properties of the neem tree, but it is the neem oil that works. Neem oil, like any essential oil for that matter, is very concentrated. ie it takes a lot of the plant to create a small amount of oil. I think you are better off to use keep your neem trees as is, and buy actual neem oil for using as an "insecticide""

Here is a link that might be useful: neem oil