Ranunculus asiaticus, also called Persian Buttercup, is a perennial plant known for its blooms. Ranunculus plants are easy to grow and care for, but there are a few problems that plague this species. The best way to ensure a healthy ranunculus plant is to recognize the signs of pests and diseases and treat them to avoid more serious problems.
Ranunculus has large, full flowers with thin, delicate petals. The flowers come in a variety of colors including yellow, orange, salmon, pink and white. They range in height from 12 to 18 inches and are about 12 inches wide. They do well in full sun and moist, well-drained soil. Several diseases and pests can cause problems for ranunculus.
Aphids are small, soft-bodied sucking insects that affect ranunculus. They can be brown, black, or green. They attack the leaves of ranunculus and suck fluids and nutrients from it. This can lead to stunted growth and leaf drop. They also produce a substance called honeydew, which attracts ants and can lead to a condition called sooty mold. Sooty mold produces a black substance on the leaves of ranunculus that blocks sunlight and prevents photosynthesis.
Spider mites are small, spider-like sucking insects that latch on and suck nutrients from the leaves. They can also transmit viruses to ranunculus. Heavy infestation is possible because the females lay up to 200 eggs in a 30-day period. Infestations can cause leaf drop and plant death. Spider mites also produce a web that can cover leaves and blooms.
Powdery mildew is a fungus more commonly formed in areas of poor air circulation and not enough sunlight. It is common in areas with warm, humid days followed by cool nights. This fungus grows on the surface of the leaves of the ranunculus and can cause leaf drop and wilting.
Rust is another fungal disease that causes small orange, brown or yellow spots on the bottom of the leaves. The spores are easily spread by splashing water and rain. Rust commonly affects ranunculus when the humidity is high or in times of excessive rain. It can lead to leave drop.
Mollusks such as slugs and snail are attracted to ranunculus. They eat holes in the leaves and can bite through entire stems. They favor moist climates so, it is important to keep the soil around the Ranunculus well-drained.