Lime sulfur sprays are usually sprayed on dormant trees. Since the chemical can burn leaves it is not recommened to be sprayed after the trees leaf out. However, if sprayed on trees that have leafed out the rains during tghe growing season will have washed any residual off so I would doubt that you would have any left to be concerned about.
What was the reason for spraying the trees.

The spray was sprayed on at the END of the growing season but before most of the leaves were off the tree (October). It was applied to control insects and fungus that may overwinter on the bark. I live in a semi-arid area and there has not been a lot of rain since it was a applied. I could smell it everytime I walked into my yard and/or raked leaves. I think I will err on the side of caution and not use my leaves in the compost.

I haven't worked with lime sulfur, but it appears to be calcium sulfides. Calcium and sulfur are both present in soil and are not particularly toxic in and of themselves. I would think this would biodegrade in an aerobic compost pile; specifically, the sulfide would be oxidized and form just a wee bit of sulfuric acid, and eventually end up as harmless calcium sulfate, or gypsum. My gut feeling is that it will have virtually no noticeable effects on your compost. I doubt that they spray much actual mass of calcium sulfide compared to the mass of leaves.

If a lot of it is present, it could knock the pH down farther, but composting tends to neutralize pH. If your pile goes anaerobic, you may get some sulfurous odors.

You could always make a separate pile of these leaves and see how they do, OR mix in a lot of other stuff to dilute any potential effects.

If things compost OK, I very much doubt the compost will be harmful to plants next year.

Thanks for your solid and well thought out advice. I think you are probably correct. I nuture my red wrigglers like pets so I don't think I will add the leaves to their compost but mulch them into my flower beds etc. Since mentioning this to a few friends it seems I will now be recieving bags and bags of leaves for my compost!
Thanks again!
M

Great, nothing like free organic matter!

Lime sulfur can be sprayed at any time of year (except when trees are in flower to avoid harming pollinators). It is just a fungicide - and a natural one at that - and is used frequently to combat fruit tree ailments that can occur after leafout - like scab. One of the recommendations for treating scab is to spray just as the leaves are falling, as well as during the dormant period and again as the tree is leafing out or until the climate conditions for scab no longer exist. In my area, that was well into June this year :-)

It is sulfur that can become phytotoxic to foliage. Adding lime to the mix reduces the phytotoxicity - the more lime, the less phytotoxic the mix. The lime itself has no antipathogenic effect. It is included only to neutralize the sulfur. Copper fungicides can also produce phytotoxic results. But using them at this time of year hardly creates any sort of serious threat of phytotoxicity.

Any leaves treated with dormant spray (horticultural oil) and/or copper or lime sulfur fungicides - all of which are considered natural or "organic" controls - are harmless when included to compost in a moderate amount.

Great!

Thank you!