Hi,

I am assuming that your friend has folage mealy bugs. One should spay the folage on top, bottom of leaves and branches, also the top of the soil.

Mixed neem oil only lasts about a day. If it is concentrated and he got it a long time ago, it may not be any good any more. It would be a good idea if your friend went and got something that is new so that he knows what he is working with. That's my opinion.

Larry

Pure neem oil can be used till 2-3 years (provided it has been stored in a cool place away from sunlight), after that its effectiveness probably reduces. As Larry mentioned, the solution of neem oil should be used within a day (preferably within 8-10 hours of mixing). The ratio I use is 1 tsp. pure neem oil in a quart of warm water plus 5-6 drops of ivory liquid dishwashing soap, shake it well for the oil to emulsify and spray on the leaves or use it as a soil drench. This should not be sprayed in sun and also when it is too hot. Also it is a good idea to test it in a small area first to see if the plant reacts badly to it (some plants are sensitive to oils).