Down the Garden Path: Disease resistance for summer roses

As we move into the warmer parts of the year, many will see the roses that were so lovely in June begin to decline. Mildew, black spot or rust may appear. One way to solve the problem is to grow roses that are very resistant to disease.

Protecting your roses

Did you know that you can effectively inoculate your roses against disease? You can. One method is to use All Season Oil. It is a more refined form of dormant oil, which is used to smother overwintering insects in the spring, as well as smother disease spores. It has been used for centuries and is one of the best and safest alternatives to traditional pesticides.

It must be used when temperatures will remain below 80 degrees for 24 hours to avoid burning the foliage. For ease of use, buy one that can be attached to a hose and spray away Note: The oils are toxic to smoke bushes, so avoid them. It’s a great preventive and control for insects and disease spores.

The second weapon in your arsenal for disease prevention is sulphur, another organic substance. It prevents, and to some extent controls, all of the above diseases. Find a concentrate, buy an inexpensive spray bottle and spray the tops and bottoms of the leaves of your roses when conditions are right for disease (humid days and cool nights). Again, observe the 80-degree limit. Frankly, I almost never get around to using oil, so this is in fact my personal first line of defense.

Option No. 3 is liquid seaweed, which you can buy in concentrated form and spray on your roses from top to bottom, including the undersides. It is sold as a powder or as a liquid. It is recommended by rosarians because it boosts plant nutrition and, when regularly used as a spray, seems to keep roses largely disease free.

All of these can be found in gardening centers, hardware stores or on the internet. All can be applied with a hose-end sprayer for easy and quick application, or a pump bottle can be used. None are expensive. The other good thing about using these products is that they allow you to really look at the beautiful plant you grow and spot problems early, as well as giving you an opportunity to admire them.

Don’t use these products on roses that are dry. They will absorb too much of any product applied, including fertilizers, and then dry and burn. Treating them before or after a rainfall is a great option. Remember, always read and follow the label directions on any yard and garden product.

For information on growing roses, check out the University of Illinois Extension’s website: web.extension.illinois.edu/roses. Also, check out the University of Illinois Extension Horticulture YouTube Channel for videos on flowers and other horticulture topics.

• Have a question for the Master Gardeners? Residents can contact the Kendall County Master Gardener volunteers from 9 a.m. to 12:30 p.m. on Monday, Wednesday and Friday by calling 630-553-5823; stopping in at 7775B Route 47, Yorkville; or emailing uiemg-kendall@illinois.edu. For helpful hints on what to include in your email, visit go.illinois.edu/HelpDeskMGdkk.