Preventing disease in your roses

May 14, 2010|By Steve Kawaratani

“I breathe the morning air of the world while the scent of Eden’s roses yet lingered in it...”

— Alexander Smith

No matter the name or reputed resistance of a particular rose, insect and foliage disease are likely to come its way. Prevention is the key to keep pest and disease damage to a minimum. Naturally, a healthy and vigorous rose is much more likely to ward off problems than one that is under stress from lack of water or nutrients.

During warm weather roses should receive one to two inches of water per week. Roses thrive on water — adequate watering is more important than fertilizer for growth! Heirloom Old Garden Roses in Oregon recommends an empty tuna fish can in the rose garden to monitor the quantity of water applied.


Most roses also require regular applications of fertilizer to reach their full potential and produce wonderful flowers.

During the next four weeks, a water soluble, balanced fertilizer such as Miracle Gro “For Roses” or Nurseryman’s Rose food should be applied the first week. Midway through the month, apply half a cup of Epsom salts, an essential element in the growth process of roses.

Good cultural practices include watering correctly. Watering overhead only in the morning, so the foliage can dry out prior to the evening, can prevent some diseases.

Watering carefully with a soft nozzle will eliminate soil or mulch from splattering on leaves. This reduces the opportunities for diseases, such as black spot, from gaining a foothold.

Pest management begins with controls other than chemicals. This may involve hand picking worms or water-washing aphids from your roses.

Natural controls like ladybugs and praying mantis can also keep insects pests under control. However, there are those times when an invasion of pests will overwhelm such nontoxic practices.

Although I don’t necessarily espouse establishing a regular spray schedule for roses, you may never see any evidence of problems if you spray your plants every two weeks with a systemic rose product.

However, remember that this chemical will kill both pests and beneficials.

All garden chemicals should be applied thoughtfully and carefully.

Look for next week’s column to highlight control of rose pests and diseases.

To describe roses as romantic is to open them and myself to a degree of misunderstanding... but certainly they are the evocative flowers of association.

Beyond their unquestioned beauty, the heavenly scent of our roses keeps me lingering in my garden each morning, and simply because I still enjoy being in Catharine’s and their company.

See you next time.

STEVE KAWARATANI is married to writer Catharine Cooper. He can be reached at (949) 497-8168, or e-mail to .

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