CONSEQUENCES OF PHYTOPHTHORA CITRICOLA OCCURRENCE IN ORNAMENTAL NURSERY WATER CONTAINERS

Contaminated irrigation water is the primary source of Phytophthora diseases of many plants, including ornamentals. In this study, occurrence of Phytophthora species in ornamental nursery water ponds and development and spread of tip blight of Thuja occidentalis and Buxus sempervirens were determined. Phytophthora species, but mainly P. citricola, were detected from water of 4 nursery ponds during all year round. The lowest number of necrotic spots on rhododendron leaves, used as the bait, was noticed in July whereas the highest in September. In favourable conditions for the Phytophthora development and sprinkling of plants with ponds water, tip blight symptoms on T. occidentalis spread very quickly from 5% to 30% of affected plants after 8 days. On B. sempervirens the disease spread slower but within almost 4 months shoot blight was noticed on more than 9% of observed plants.