Tree & Shrub Disease Control

Powdery Mildew

This is a common disease for ornamental plants caused by fungi. Powdery Mildew appears as a dusty white to gray coating over leaf surfaces or other plant parts. This disease rarely causes serious damage but can discolor leaves, disfigure shoots, and deform flowers. In most cases, this fungal growth can be partially removed by rubbing the leaves together. Powdery Mildew will begin as discreet, usually circular, powdery white spots. These spots will expand, producing a continuous matt of mildew. Infected plants often turn yellow and may even blacken from infection.

Houseplants commonly affected are African violets and begonias. Outdoors, a variety of plants can be affected, but most often lilacs, phlox, some rose varieties, and fruit trees seem to be most susceptible.

Leaf Spot

This disease is causes by bacteria. Leaf Spot is most active under hot, humid conditions. Leaf spots first appear as water-soaked spots but then turn reddish-brown to black in color that are somewhat circular in shape. Yellow margins usually appear around the spots.

Phytophthora Root Rot

This is almost always the result of overwatering, root damage, or prior drought stress. Phythophthora Root Rot is a very difficult to control fungal disease that affects a wide range of plants in North Carolina. Azaleas, rhododendrons, dogwoods, hemlocks, Japanese hollies, and junipers are just a few of the plants affected.

This disease is most active in warm soil temperatures with high soil moisture. Plants under stress from drought, defoliation, low soil aeration, and other stress agents are most prone. Symptoms of root rot vary depending on the plant species. Symptoms include a reduction in shoot growth like small leaves, thinning of the crown, twig and branch dieback, and eventually death. Diseased roots are reddish brown and brittle. Watering does little to restore the leaf. On rhododendrons, leaves rapidly wilt, droop, and eventually die.

Botrytis Blight

Also known as gray mold, this is a fungal disease and is one of the most common diseases in greenhouse crops, including azaleas, begonias, carnations, chrysanthemum, petunias and rhododendrons. This disease causes water-soaked tan, brown, or gray spots or streaks to appear on the flower petals, leaves, buds, and stems. Most common are translucent or grayish spots. Flowers can be deformed.

This disease is most active during wet or humid weather conditions. Flowers are especially susceptible under cool, wet conditions with high humidity. Leaf wetness periods of more than four hours increases the chance of infection.