2018 ASHS Annual Conference

Plant pathogens can cause crop losses and reduce the quality of greenhouse and nursery plants. Plant pathogens can also be moved long distances by the plant trade, potentially spreading diseases to new hosts and habitats. Phytosanitary approaches based on quarantines and end point inspections have reduced but not eliminated the interstate spread of Phytophthora ramorum with nursery stock, for example. It is therefore important for plant production facilities to identify potential sources of contamination and to take corrective measures to prevent disease. We applied a systems approach to identify sources of contamination within horticultural nurseries and demonstrated that irrigation water can be an important source of contamination by waterborne plant pathogens such as Phytophthora and Pythium species. We will present case studies from nurseries in Maryland, South Carolina, Oregon, and California to illustrate how recycled irrigation water contributes to the spread of waterborne pathogens, and show how nursery management practices can reduce disease risk.