I have no idea, and as you said it is hard to tell b/c it always have that nasty smell. I always used the concentrate, which I mixed with water, or Botani Wipes. Sorry I can't help. But I too would love to know the answer.

Sarah

you can use it. I have some that has to be over 8 years old that I use occassionaly. I use mostly Neem II now. It is put out by Green Light. It cost about $8 a bottle Shake the bottle and it is ready to use no mixing and no clogged nozzels. I have two bottles scattered thru my growing areas. 70% isopropal alcohol bottle and a bottle of Neem II. As soon as I see a critter I hit it with the alcohol. After that dries it gets a NeemII bath.

Even rancid neem oil should work as it's the oil that smothers the insect, so if it's rancid it shouldn't make any difference.

Thanks for all the advice.

Back when I was searching for a cure for my original scale problem I found an interesting thread over on the houseplants forum. It explains in great detail how neem oil works to control critter infestations. It's more than just the smothering from the oil, but also among other things the action of a chemical that inhibits reproduction. I'm sure the smothering action of the oil still works, but if the active chemical has degraded over the last few years then it won't be any more useful than standard veg oil.

It doesn't sound like it can cause any harm so I used it last night. Crossing fingers....

Tyler

Here is a link that might be useful: About Neem Oil

I did some google searching. Most sites give a shelf life of 1 to 2 years. Not much information as to how it's usefullness declines during/after that time period though. Also found some very interesting non plant related uses.

Tyler