Submitted to: Experiment Station Bulletins
Publication Type: Experiment Station
Publication Acceptance Date: 1/8/2019
Publication Date: 2/1/2019
Citation: Porter, L.D., Paulitz, T.C., Schroeder, K. 2019. Lentil disease diagnostic series: Pythium seed and seedling rot. Experiment Station Bulletins. PP1913.
Interpretive Summary: A short and concise disease diagnostic card was developed to help growers rapidly diagnose Pythium seed and seedling rot on lentil through descriptions and color photographs of disease symptoms commonly associated with the disease. The card also provides important factors that favor disease, facts regarding how to manage the disease, and describes a disease that could potentially be mistaken for Pythium seed and seedling rot.
Technical Abstract: Pythium seed and seedling rot caused by Pythium ultimum, P. irregulare, P. aphanidermatum and other Pythium spp. is a major disease of lentil. The following symptoms typically are associated with Pythium infection: 1) poor emergence, 2) rotted seed with light brown discoloration of inner tissue, 3) stunted plants with yellow or purple leaves developing from the bottom to top of plant, and 4) brown/black discoloration of roots with lateral roots appearing pruned. Factors favoring disease development include: 1) conditions delaying emergence such as cool, compacted soil and poor seed vigor, 2) presence of metalaxyl-resistant Pythium in soil, and 3) cool water-saturated soils at or near planting. Important facts about Pythium seed and seedling rot are: 1) there are highly effective chemical seed treatments available for management of both metalaxyl-resistant and sensitive Pythium, 2) avoid planting into wet soils that promote soil compaction and reduce plant vigor, and 3) Pythium can often be confused with Aphanomyces and Rhizoctonia root rots and damage from water logging.