Please help me understand lime sulfur and dormant oil

newbieroseloverJanuary 26, 2005

Hello everyone, could you please tell me how and when to use LS and dormant oil to prevent blackspot? Is lime sulfur considered organic? Also, some of my roses have retained green leaves and new growth over the winter. Does that make a difference whether I can use these treatments?



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Calcium poly sulfide (lime sulfur) is considered an organic control. Since horticultural oil is a highly refined petroleum product, you will get qualms about its use by organic purists but it is approved for organic purposes also.

These are products best used in the dormant season, IMO, as their use during the growing season can cause phytotoxicity. They are effective in helping to control fungal problems if overwintering spores are present but as with all topical fungicides the preventative will only last so long. Since black spot is typically encouraged by warmer weather and humid conditions, you will have to look for another treatment option later in the season.

Remove any foliage still remaining on the bushes and clean up any fallen material underneath them and destroy before spraying. Don't worry about buds or new growth - it is still January and these will likely be gone/damaged by cold before it's time to prune anyway. Spray the canes thoroughly and if the area underneath is not heavily mulched, spray the ground as well to get any spores lurking in that area.

Check out the other thread "organic control of BS on Austrian Copper....."

    Bookmark   January 26, 2005 at 8:51AM
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thank you, very helpful!

    Bookmark   January 26, 2005 at 11:06AM
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