The dog days of summer are around the corner, and with the hot dry weather comes trouble for many plants in the form of bacterial and fungal diseases that disfigure and take their toll on the garden. While some folks take these problems in stride and overlook imperfections, others choose to use chemicals to control the problems.

The good news is that today there are a variety of products that, when used properly, are safe to use and effective.

Prevention of course is at the top of the list, and two most common mistakes many gardeners make come to mind. Over-fertilizing produces large plants, but fast lush growth produces leaves with little protective cuticle to protect from disease. Fungal disease thrives in wet environments so when possible, water in the morning so the foliage has time to dry before nightfall.

Timing is another key to success when it comes to disease control. Most fungicides are protectants – they don’t kill the spores, they prevent them from spreading so most fungicides should be used as soon as the pathogens strike. Checking the leaves and flowers of vulnerable plants often may make the difference between control and death, especially vulnerable plants such as cucumbers and zukes.

Bacillus subtilis is a biological fungicide made of a naturally occurring bacterium that’s used to control a wide variety of bacterial and fungal diseases, including powdery mildew and downy mildew. Sold under the brand names of Serenade and Natria Disease Control, these products are OMRI listed and safe for use on edibles, as well as ornamentals. They have no negative impact on insects as well as pets and people.

For more information on the use of these products, go to garden/en/products/natria/q-a/ or serenadegarden.

Take note that not all fungicides or bactericides work on all diseases, nor can they be safely used on all plants. So to get the control you want and not damage your plants, be sure to read the entire label and follow the directions for use.

Copper based products have long been used to prevent a variety of fungal and bacterial diseases but they have several serious drawbacks. First, they are a preventative only and will not control diseases once they strike. More importantly, they are toxic to humans and mammals if ingested or inhaled and are also toxic to fish and other invertebrates and should never be used near waterways or ponds.

For more information on plant diseases and effective treatments, visit the Savvy Gardening website at /plant-diseases -in-the-garden-prevent-control/

Nancy Szerlag is a master gardener and a Metro Detroit freelance writer. Her column appears on Fridays in Homestyle. To ask her a question go to and click on Ask Nancy. You can also read her previous columns at

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