Root and crown rots, Rhizoctonia solani, Thielaviopsis basicola . The above-ground symptoms are nonspecific and include a general wilting, decline, and collapse of the foliage and the entire plant. This general droopiness or flaccid appearance is often accompanied by browning and rotting of the roots and the crown. Yellowing and death of the outer leaves follows, until finally the entire plant is dead. Blackened stem lesions may be present at or near the soil line.
Control can be difficult once plants are infected so prevention is important.
It is helpful to avoid overwatering, especially in heavy soils, and to avoid watering directly into the plant. Highly symptomatic plants can be rogued and removed since recovery is unlikely. Attention to spacing is also helpful since it improves air circulation between plants and promotes drying. Powdery mildew, Sphaerotheca White, powdery spots or patches develop on leaves and occasionally on petioles. Symptoms often first appear on the upper surfaces of the leaves and are usually most pronounced during hot, humid weather.