Submitted to: Idaho Winter Commodity School Proceedings
Publication Type: Proceedings
Publication Acceptance Date: November 1, 2003
Publication Date: January 21, 2004
Citation: Munyaneza, J.E. 2004. Leafhopper transmitted diseases: emerging threat to Pacific Northwest potatoes. Idaho Winter Commodity School Proceedings. 36:141-150. Interpretive Summary: Diseases caused by phytoplasmas are increasingly on the rise in the Pacific Northwest potatoes. Recently, a serious epidemic of purple top disease of potato occurred in the Columbia Basin of Washington and Oregon in 2002 growing season and caused very significant losses to potato fields. The same disease was observed in 2003 growing season, especially in organic potato fields. Potato fields with similar disease symptoms were also reported in some parts of Idaho. Symptoms in affected potato plants include a rolling upward of the top leaves with reddish or purplish discoloration, moderate proliferation of buds, shortened internodes, swollen nodes, aerial tubers, and early plant decline. Investigation of the cause(s) of the disease indicated that leafhopper transmitted phytoplasmas may have played a significant role in this disease epidemic. Information on insects vectoring this purple top disease of potato and their population dynamics is crucial to appropriately manage this disease in potatoes. Leafhopper sampling we conducted at several locations throughout the south Columbia Basin of Washington and Oregon during the 2003 growing season provided information on the population dynamics of different leafhopper species in the area.
Technical Abstract: Leafhoppers are strongly suspected to be the vectors of a recent epidemic of purple top disease of potato that occurred in the Columbia Basin of Washington and Oregon, and possibly in Idaho. A phytoplasma belonging to the clover proliferation group (16SrVI-A) was detected in diseased potato plants collected in the Columbia Basin and is thought to be the disease causal agent. Results from our leafhopper monitoring and sampling in and/or near affected potato fields during the 2003 growing season throughout the south Columbia Basin indicated the presence and population dynamics of several leafhopper species, including Circulifer tenellus, Macrosteles spp., Ceratagallia spp., Dikraneura spp., Exitianus exitiosus, Ballana spp., Colladonus spp., Amblysellus spp., Paraphlepsius spp., Balclutha spp., Latalus spp., Empoasca spp., and Erythroneura spp. Leafhopper species vectoring this disease have not conclusively been identified.