BIORATIONAL CONTROL METHODS FOR INSECT PESTS OF POTATO
Location: Fruit and Vegetable Insect Research
Title: Incidence of the Beet Leafhopper-Transmitted Virescence Agent Phytoplasma in Local Populations of the Beet Leafhopper, Circulifer tenellus, in Washington State
Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 22, 2008
Publication Date: March 15, 2010
Citation: Munyaneza, J.E., Crosslin, J., Upton, J.E., Buchman, J.L. 2010. Incidence of the Beet Leafhopper-Transmitted Virescence Agent Phytoplasma in Local Populations of the Beet Leafhopper, Circulifer tenellus, in Washington State. Journal of Insect Science 10:18, p 1-10. Online: insectscience.org/10.8.
Interpretive Summary: In recent years, potato growers in the Columbia Basin of Washington and Oregon have experienced outbreaks of the potato purple top disease. These outbreaks have caused significant yield losses and reduced tuber quality. It was determined that the beet leafhopper-transmitted virescence agent phytoplasma (BLTVA) was the causal agent of the disease and that the beet leafhopper was the major vector of the phytoplasma in this important potato growing region of the US. Researchers at USDA-ARS Wapato and Prosser conducted studies to determine incidence of this plant pathogen in beet leafhoppers invading potatoes throughout the growing season. It was discovered that a large proportion of these insects were infected with the phytoplasma. These findings will help in developing action thresholds for beet leafhopper control to reduce incidence of purple top disease in potatoes.
Phytoplasma diseases are increasingly becoming important in vegetable crops in the Pacific Northwest. Recently, growers in the Columbia Basin and Yakima Valley experienced serious outbreaks of potato purple top disease that caused significant yield loss and a reduction in tuber processing quality. It was determined that the beet leafhopper-transmitted virescence agent (BLTVA) phytoplasma was the causal agent of the disease in the area and that this pathogen was transmitted by the beet leafhopper, Circulifer tenellus Baker. To provide the most effective management of phytoplasmas, timing of insecticide applications targeted against insects vectoring these pathogens should be correlated with both insect abundance and infectivity. Beet leafhoppers were collected from a potato field and nearby weeds in Washington throughout the 2005, 2006, and 2007 growing seasons and tested for BLTVA by PCR to determine the incidence of this phytoplasma in the insects. In addition, overwintering beet leafhoppers were collected throughout Columbia Basin and Yakima Valley and tested for BLTVA to investigate if these insects might constitute a source of inoculum for this phytoplasma from a season to the next. Results showed that 29.6% of overwintering leafhoppers collected near potato fields carried the phytoplasma. BLTVA-infected leafhoppers were also found in both potatoes and nearby weedy habitats throughout the growing season. PCR testing indicated that a large proportion of beet leafhoppers invading potatoes were infected with the phytoplasma, with an average of 20.8, 34.8, and 9.2% in 2005, 2006, and 2007, respectively. Similarly, BLTVA infection rate in leafhoppers collected from weeds in the vicinity of potatoes averaged 28.3, 24.5, and 5.6% in 2005, 2006, and 2007 respectively. Information from this study will help develop action thresholds for beet leafhopper control to reduce incidence of purple top disease in potatoes.