Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 3/17/2006
Publication Date: N/A
Technical Abstract: One-inch square leaf pieces of Syringa vulgaris infected with Phytophthora ramorum were placed on the surface of 4” nursery pots containing healthy lilacs. The pots were then subjected to frequent overhead irrigation or twice-a-day trickle irrigation for a month. Periodically leaf pieces were shaken in sterile distilled water and aliquots plated on selective media to quantify propagules. A second set of experiments compared trickle irrigation at 1, 2, and 3 times a day, and a third incubated plants at different temperatures. A final experiment placed 0-16 leaf pieces in each pot and examined infection of roots. Leaves kept under very wet conditions produced copious numbers of sporangia during the first week, and afterward, as the leaf decayed, released chlamydospores; root infection was seen under these conditions. Fewer sporangia were produced with trickle irrigation, with the most produced when plants were watered 3 times a day. A greater number of sporangia were produced when plants were incubated at 10 C than at 15, 20 or 25 C. Some root infection was seen in plants with different numbers of leaves left on the pot surface, but no relationship with leaf number was observed.