June 03 2015
commercial maintenance

Controlling Fungus During the Hot Months

Nothing puts a damper on an otherwise beautiful yard or garden quite like fungus. It comes in gradually. It grows quietly. And it can quickly become a major nuisance if not properly addressed.

So how can you combat this looming threat?


During the spring and summer months, when plants start coming back in bloom and taking root, is when the beginnings of fungus are most likely to take hold.

The shifting weather patterns, increased humidity, and introducing new plants to your immediate ecosystem is where problems can begin to fester. Most fungal diseases in plants are spread by wind and splashing water containing microscopic mold spores.

These spores take hold during times of consistent moisture, where they can find a surface and a food source to begin matriculating. Overwatering, improperly watering, or watering at the wrong time of day can all lead to mold growth.


When it comes to mold, detection and immediate action are your best friends. The three most common fungus types to appear in flowering plants are Powdery Mildew, Boytris and Black Spot. Knowing what to keep an eye out for will help you be able to properly diagnose and act.

Powdery Mildew

A white, powder-like coating on leaves and plant leaves, stems and even fruit. Affected areas turn yellow then eventually brown. Not fatal, but damaging to the plant’s immune system. Can lead to early bud drop and hampered flower quality.  

  • Annuals most vulnerable: Zinnias, snapdragons, and verbena are flowers with great vulnerability to powdery mildew.
  • Perennials most vulnerable: delphiniums, lungwort, bee balm, and garden phlox.


Powdery Mildew grows when conditions with high humidity, low amounts of sunlight, and moderate temperatures. New plants, which many times are over-fertilized, are particularly susceptible.

Make sure plants are positioned so they can receive at least 6 hours on sunlight. Proper spacing for air circulation is also important.

Boytris Blight (aka Gray Mold)

Appears first as a white growth before darkening to a grayish color on dying or rotting foliage and fruit. It is a fast-growing, infectious mold that can grow when plants are left wounded or in a state of decay in a moist environment.

  • Affects a wide range of flowers with thick petals (begonias, peonies, geraniums)
  • Affects many fruits and vegetables after they’re moved into cool places for storage.


Avoid injuring plants in any way and leaving large stubs of plant tissue when pruning or cutting. Plants should be positioned in a way that they may receive good air circulation.

Gray Mold can affect any part of the plant above the root. Allow for proper spacing between each plant to promote drying and full sunlight. Also, remove debris and dead plant parts that may gather between healthy plants.

Black Spot

Characterized by round black spots on leaf surfaces, in which foliage then turns yellow before falling off. Heavily infected areas may show black blotches instead, a build up of several black spots. The fungus requires at least seven hours of wet conditions to

  • Affects flowering plants, particularly roses.


Black Spot develops quickest in warm, wet weather. Remember to water plants at soil level and not to wet the foliage part of flowers.

Spray Neem oil every 10-15 days during growing season. Avoid improper irrigation, space properly and plant roses and other susceptible flowering plants in areas they can receive six to eight hours of continuous sunlight.

Immediately remove foliage that shows signs of Black Spot.


Many molds start becoming noticeable only after it is too late, in mid to late summer. A proper maintenance plan for your landscape will include proactive measures for potential fungus growth.

At High Tech Landscaping, our expert team is no stranger to handling diseased or infected landscape rejuvenation. Our extensive service offerings can provide the right attention for whatever your landscape may require.

The best defense, however, is a regular regiment of proactive plant and foliage care. That means proper irrigation, as well as a Plant Health Care Program that’s built for every season. When purchasing your own plants and flowers, always select plants that are healthy from the get-go. And speak with one of our landscape specialists if you detect the first signs of fungus this summer.