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Roses knew about this fad long before we rose growers caught on ... every winter they would look forward to getting a good dousing of some ‘aromatic’ concoction to ward off the fungal evils of the season. We call them ‘dormant sprays.’

While dormant sprays are commonly used on fruit trees, they can also benefit roses and other ornamental shrubs that might develop insect or fungal disease problems as the cooler winter weather arrives and then makes way for the warmer spring. Dormant sprays should only be used in conjunction with good garden sanitation. Be sure to rake up and dispose of all fallen leaves and debris - they may harbor fungus spores and overwintering insects. Sanitation and dormant sprays are the "ounce of prevention" that will save you a pound of cure next spring.

Two different types of fungicides are used in dormant spray products. You should use each of them in different applications. First one in early winter, the other in early February.

Sulfur-based

The most common dormant spray is lime sulphur, combined with a horticultural spray oil. This combination effectively controls blackspot and other fungal diseases whose spores can overwinter and reinfect the plant in spring. Spores that have fallen to the ground or are on the undersides of leaves and inbark crevices will activate when warm weather starts and the disease will strike again.

The lime sulfur fights the fungal disease while the oil helps it stick to the plant so it won't be washed off by our winter rains. The oil spray also smothers any insect pests or insect eggs that may be overwintering on the plant. While lime sulfur smells like rotten eggs, it's relatively safe to use and is approved for use in organic gardens. Be careful not to get it on painted surfaces, as it will stain them.

Copper-based

These are products such as Microcop (copper sulfate) or Tribasic copper sulphate combined with a spreader-sticker such as Sta-Stuk. Copper sprays effectively control fungal diseases that overwinter by killing the spores. The copper is toxic to fungus organisms. This one is NOT rated for use in organic gardens. Be sure to spray all plant surfaces (stems and any leaves remaining) as well as the bare soil around the base of the rose bush.

As with all pest control sprays, follow instructions on the spray label and wear appropriate protective clothing when applying these materials.

Both of these products mix easily (follow the directions) and cleanup is accomplished with mild soap and water. If there are any leaves still on the rose bush, this stuff will kill the leaf. Then it will fall off ... then you have to pick it up and throw it away. It’s easier to strip off the leaves before you spray!

Dogs and cats aren’t interested in these sprays, birds and worms won’t touch them, they won’t harm humans who don’t drink them or rub them all over their bodies or inhale them as some sort of mind-bending hallucinogenic "trip." Be normally careful---wear goggles to keep mist out of your eyes, wash your clothes and yourself after you clean up your sprayer.

Your roses will appreciate your concern for THEIR health as well as your own!

Last updated: 3/7/09
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