Symptoms and Control Methods of Root Rot in Impatiens

It occurs in all impatiens cultivation areas and can cause plant death.

Symptoms mainly infect the root crown and lower parts of impatiens, with grayish-brown lesions appearing initially, which then rapidly expand, causing the roots to become slightly swollen and turn dark brown and rot; after the root crown tissue rots, it loses water and appears shrunken. The aboveground parts show sudden wilting of diseased plants, gradually worsening, resembling temporary water shortage, but this is irreversible after watering.

Disease pattern: the pathogen is a fungus, Rhizopus arrhizus-like. The pathogen overwinters in the soil with diseased plant residues. Soil that is too wet, high temperatures, plants being too densely planted, and poor ventilation all favor the occurrence of the disease. Generally, the disease is more severe in July to August.

Control Methods

(1) Strengthen cultivation management. Impatiens should be planted in soil that is sunny, fertile and loose, well-drained, and neutral to slightly acidic, with good ventilation. Do not plant in semi-shaded or relatively wet places, to avoid excessive growth, lodging, and poor flowering.

(2) Keep the flower garden clean, promptly remove fallen leaves, apply fully decomposed organic fertilizer, and appropriately apply more potassium fertilizer to promote new root growth and prevent root rot.

(3) When a diseased plant with wilting of the whole plant is found, promptly dig it out together with the roots and surrounding soil and bury it deeply elsewhere, and pour 1% copper sulfate solution into the original soil pit for disinfection; after drying in the sun for 7 days, replant. If it is in a pot, the soil in the diseased plant's pot should be discarded and not used; soak the flower pot in 1% copper sulfate solution for 1 hour for disinfection, then expose it to sunlight for 7 days before changing to new soil for planting.