SUMMER DISEASES IN THE GARDEN

By O’Bryan, Horticulturalist

When the Summer heats up, the disease kicks in and can really do a number on your gardens, both ornamental and vegetable in nature.  Disease can not only make your plants look sad and damaged, but can possibly kill them if untreated.  There are several types of disease to look out for in your garden, mostly fungal in nature.  Let this article serve as a guide for identification and treatment.

Plant fungus is typically caused by hot, humid conditions and poor watering practices.  Splashes of water on diseased leaves is the best possible way to spread fungi. To control the spread of various fungi, mulch the ground well, and water at the soil level, where the roots can get the most benefit. This will not keep disease away, but will control the spread.

If fungi have already taken over, there are many ways to deal with it.  Here is a list of fungi, how to identify them and what products help to control it.

Powdery Mildew

This fungus looks like someone dumped a bottle of baby powder all over the leaves of your plant.  You will almost always find this fungus on peony, dogwood, phlox and most cucurbit species in the garden like squash and cucumbers.

Powdery mildew usually shows up when there are cool nights and hot days, so Spring and early Summer is when it will rear its ugly head.  If you find you have this fungus on your plants, rest assured, it will kill but may damage the leaves to the point where it won’t look its best for the rest of the season.  Use Serenade for the control of powdery mildew.  This product is an organic biocontrol, specifically a harmless bacterium that likes to eat fungus.  It is great in the landscape and the vegetable garden.

Black Spot

The problem with roses is that most of them inevitably get black spot, a fungal disease that can make leaves turn yellow and eventually fall off if the disease is unchecked. When a plant loses too many leaves, it can’t photosynthesize and will suffer for it.

The good news is that black spot is very easy to take care of.  Keep an eye on your roses and at the first sign of the disease, spray with neem oil, another organic fungicide with the added benefit of a pesticide that can control chewing pests such as aphids, who often devour rose buds.

Downy Mildew

Downy mildew prefers cold and rainy weather.  It first shows up on the underside of leaves as a fuzzy looking blue-gray substance.  Although not a true fungus, downy mildew is closely related and even spreads by spores like a true fungus.

Downy mildew can be found on many vegetable crops and can present itself as yellow spots, the second sign you have the disease.  If you find you have this disease in your veggie garden, use a copper based, organic fungicide for optimal eradication.

Boytritis

Also known as gray mold, boytirtis can show up anywhere there has been too much watering going on.  This is especially spread in greenhouses and can be taken home by unsuspecting shoppers.  This fungus is spread by the tiniest drops of water so it can take over and kill a plant very quickly.  Geraniums in general tend to harbor this disease so check out the insides and older leaves toward the bottom to see if they geranium you are buying has signs of the disease.

If you find you have the disease at home, remove the infected leaves and treat the plant with Captan, a wettable powder fungicide that works against this specific disease.

Protecting plants from disease takes diligence and patience, especially when the season is more wet than usual.  With these suggestions, you should be able to combat fungi and keep your plants healthy and happy.