Black Root Rot

• Black root rot damages the root of the plant, hindering its ability to absorb nutrients. Yellow leaf growth is often a sign of this disease. The roots of plants infected with black root rot are black, gray or off-white, as opposed to the white roots of healthy plants. Too much moisture and extreme temperatures are two factors that cause a plant to develop black root rot. Fungicides effectively fight this disease if used as a preventative measure or at the first sign of infection.
  
  

Powdery Mildew

• Powdery mildew can occur on many types of plants and is characterized by a powdery white fungus on plants' lower leaves. The leaves may become twisted before they wilt and die. Plants exposed to high relative humidity at night and low relative humidity during the day are more likely to develop this condition. Fungicide application helps inhibit the spread of powdery mildew.
  
  

Downy Mildew

• Downy mildew usually appears first on the underside of the plant's leaves and may have a bluish tint. Yellow spots appear on the top of the leaves, and the infected leaves sometimes become twisted and then die. To prevent downy mildew, make sure your plants receive good air circulation so that their leaves can quickly dry after rainfall or watering. If your plants become infected, treat them immediately with a fungicide.
  
  

Rhizoctonia

• Rhizoctonia, which is a fungus, causes root and stem rot. It likes warm, moist soil. Plants infected with this fungus wilt in the middle of the day, and you'll notice stem rot near the soil line. Once this fungus starts to grow, it usually spreads quickly, so it's important to treat the plant with a fungicide as soon as you notice its development.