Dormant oil is usually horticultural oil PLUS lime-sulphur.

The oil as you noted is not harmful but the lime sulphur WILL
cause leaves to fall off.

I've tried white oil here but it needs to be reapplied
after each rain. Also once the insects have hatched
it has no effect.


--
Theo in Zone 5
Kansas City

"Daniel Hanna" wrote in message
home.com.au...
In R & L Porter wrote:
I was wondering if an application of dormant oil in the
Spring would help smother the larvae -- on the canes
and on the surrounding earth. Any ideas, opinions?

We've had something like this discussion before. I've always been
intrigued by the American term 'dormant' spray. If what we're talking
about is a petroleum oil, water miscible spray then it's the same as the
white oil and pest oil sprays sold in Australia. See eg:

http://www.amgrowgardenking.com.au/p...s_whiteoil.htm

On roses, this stuff is great all season. Without being toxic it
manages to smother aphids, scale insects, mites, mildew, black spot and
others. I can see absolutely no difference in effect compared to neem
oil (which is trendy but works basically the same way, at 5 times the
cost).