Diseases/Pests/Troubleshooting: Early Sunrise coreopsis is a hardy full sun performer known to be tolerant to heat, drought, and poor and sandy soils. Do not overwater because coreopsis will be susceptible to powdery mildew, leaf spots, and rust in overly saturated and poorly drained gardens. Deadhead plants often to promote growth and minimize self-seeding, which may become weedy. Coreopsis has no serious insects, pests, or diseases.