Quantitative assessment of Anguina sp. and Rathayibacter rathayi in Dactylis glomerata seed production fields in Oregon and estimates of yield loss

Abstract

Anguina sp. is a nematode that infests the inflorescence of orchardgrass and forms galls that replace the seed. Anguina sp. is also a vector of the bacterial pathogen Rathayibacter rathayi, which causes galls or gummosis in orchardgrass (Dactylis glomerata) panicles. The percentage of orchardgrass panicles infected or percentage of seed loss from Anguina sp. or R. rathayi in five commercial orchardgrass seed-production fields in Oregon during 2003 and 2004 was determined. The percentage of panicles with Anguina sp. ranged from 9 to 24%, although the percentage of seed replaced by Anguina sp. was less than 0.2%. The number of galls per panicle ranged from 1 to 29. However, more than 50% of Anguina-infested panicles contained only a single Anguina gall and few panicles had eight or more galls. The percentage of panicles with R. rathayi ranged from 3 to 27%. Percentage of seed loss from R. rathayi ranged from 0.1 to 7.3%. Seed loss in orchardgrass seed-production fields assessed for both Anguina sp. and R. rathayi was found to be as great as 8%. The number of Anguina galls remaining in fields following harvest ranged from 0 to 40 per square meter.