American Tree Experts

A Guide To Common Plant Diseases And Their Treatments

Gardening made easy – A practical guide to common plant diseases and their treatment

Plants are vital in maintaining ecological balance and sustaining life on Earth. However, like any living organism, plants are susceptible to diseases affecting their health and growth. Whether you are a seasoned gardener or new, this guide provides valuable insights to help you identify and address common plant diseases to keep your plants healthy and disease-free.

Powdery Mildew

  • Powdery mildew, with its distinctive white, dusty coating, affects various plants, including fragrant lilacs, apples, grapes, cucumbers, peas, daisies, and roses. This common plant disease can severely compromise the health of plants.


  • A proactive approach involves raking and promptly disposing of infected leaves to minimize the spread of spores. Additionally, ensure your plants enjoy optimal conditions by providing good drainage and ample air circulation. Adopt a watering routine that avoids overhead irrigation at night.

Instead, mid-morning watering sessions are a better approach as they allow the leaves to dry before the evening. Commercial fungicides tailored to powdery mildew are available for those seeking more targeted interventions. Alternatively, you can use a natural remedy recommended by gardening experts.

Downy Mildew

  • Downy mildew is challenging for plants, including impatiens, pansies, columbine, grapevines, lettuce, and cole crops like broccoli and cauliflower. Unlike powdery mildew, downy mildew is triggered by fungus-like organisms.

It typically emerges in damp conditions, causing discoloration on the upper part of leaves and the development of white or gray mold on the undersides.


  • Addressing downy mildew involves simple practices. When possible, choose plant varieties that show resistance to this condition. While specific fungicides for downy mildew are unavailable, cultural approaches can be effective. If your plants are affected, promptly remove and dispose of infected leaves or even entire plants if the infestation is widespread.

Follow these practices to prevent the recurrence of downy mildew:

  • Avoid overcrowding plants
  • Refrain from evening watering
  • Practice crop rotation for edibles yearly

With these practical measures, you can mitigate the impact of downy mildew and promote the well-being of your ornamental and edible plants.

Black spot

  • It is a fungal disease commonly affecting roses, various other flowers, and fruits. While it is not fatal to plants, its presence weakens them and makes them more susceptible to additional issues. In cooler, moist conditions, small black spots appear on the foliage, turning the affected leaves yellow and eventually detaching them from the plant.


  • It is crucial to remove and dispose of diseased canes and leaves before the onset of winter, as the fungus overwinters in these areas. Maintaining clean and dry foliage is key to preventing black spots. This can be achieved through mulching beneath plants, strategically positioning roses in the morning sun for dew evaporation, and adopting a watering method that targets the roots rather than wetting the foliage.

For those seeking additional measures, consider incorporating black spot-resistant rose varieties into your garden. Furthermore, a preventative application of fungicide can protect plants from this disease.

Mosaic Viruses

  • common plant diseasesMosaic viruses are a challenge for gardeners. It has two types: the tomato mosaic virus and the tobacco mosaic virus. The former targets tomatoes, peppers, potatoes, apples, pears, and cherries, while the latter infects peppers, cucumbers, lettuce, beets, petunias, and tobacco.


  • Various symptoms can identify viruses, including yellowing, stunted growth, deformed fruits, and diminished yield. A proactive approach involves removing and disposing of infected plants, including roots. It is advisable to avoid planting susceptible species in the same area for two years to prevent reoccurrence.

If you fear that your trees and plants are suffering from plant diseases, then waste no time and contact American Tree Experts. We provide effective and proactive Disease Management for plants and trees. Call us at (973) 744-6091 to get a free estimate of our services. We operate in Mont Clair, New Jersey, and nearby areas.

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