Curly top viruses and phytoplasmas in sugar beets, common beans, and beet leafhoppers along with vector population dynamics in southern Idaho

Authors: Strausbaugh, Carl; WENNINGER, ERIK - University Of Idaho; Jackson, Laurie; Vincill, Eric

Submitted to: PhytoFrontiers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2023
Publication Date: 1/31/2024
Citation: Strausbaugh, C.A., Wenninger, E.J., Jackson, L.K., Vincill, E.D. 2024. Curly top viruses and phytoplasmas in sugar beets, common beans, and beet leafhoppers along with vector population dynamics in southern Idaho. PhytoFrontiers. 4:1-14. https://doi.org/10.1094/PHYTOFR-08-23-0115-R.
DOI: https://doi.org/10.1094/PHYTOFR-08-23-0115-R

Interpretive Summary: Beet curly top in sugar beet and common bean is a major yield limiting disease in semi-arid production areas. The disease is caused by Beet curly top virus (BCTV) and is vectored by the beet leafhopper (BLH). Control for BCTV centers around host resistance and the use of systemic insecticide seed treatments in both sugar beets and common bean. However, the BCTV strains have been shown to vary over time and some sources of host resistance in sugar beet can be strain specific. Thus, stakeholders requested that BLH populations in southern Idaho be tracked during the 2020 and 2021 growing seasons in desert areas and sugar beet and common bean fields with yellow sticky cards to assess BLH population levels and identify the curly top virus species/strains and phytoplasmas present. Plants from monitored crop fields were also assessed for the same pathogens. Once BLH populations in Elmore Co. began increasing in May, they were present in double-digit numbers per card through the summer at all sites both years. However, the BLH numbers at other desert sites were at or near zero; local weed populations and not desert areas appeared to be the primary source of BLH in crop fields. The peaks in Elmore Co. also occurred approximately one month earlier than historical averages which puts sugar beets more at risk since host resistance at early growth stages is weaker. Both years, BCTV strains Worland (Wor) and Colorado (CO) were the primary strains in BLH and plant samples. The CA/Logan, Pepper curly top (PeCT), and Severe strains of BCTV were also detected in BLH along with Spinach curly top Arizona virus (SpCTAV). Phytoplasmas were detected in 1% of BLH samples both years. Phytoplasmas, SpCTAV, and PeCT were not detected in plant samples. This project established the curly top species/strains for which host plant resistance is needed as well as the time and areas when crops are at highest risk for infection.

Technical Abstract: Beet curly top in sugar beet and common bean is a major yield limiting disease which is caused by Beet curly top virus (BCTV) and is vectored by the beet leafhopper (BLH; Circulifer tenellus). BLH populations in southern Idaho were tracked during the 2020 and 2021 growing seasons in desert areas and sugar beet and common bean fields with yellow sticky cards to assess BLH population levels and identify the curly top virus species/strains and phytoplasmas present. Plants from monitored crop fields were also assessed for the same pathogens. Once BLH populations in Elmore Co. began increasing in May, they were present in double-digit numbers per card through the summer at all sites both years. However, the BLH numbers at other desert sites were at or near zero; local weed populations and not desert areas appeared to be the primary source of BLH in crop fields. Based on cytochrome oxidase gene, two haplotypes dominated the BLH population both years. Both years, BCTV strains Worland (Wor) and Colorado (CO) were the primary strains in BLH and plant samples. The CA/Logan, Pepper curly top (PeCT), and Severe strains of BCTV were also detected in BLH along with Spinach curly top Arizona virus (SpCTAV). Phytoplasmas were detected in 1% of BLH samples both years. Phytoplasmas, SpCTAV, and PeCT were not detected in plant samples. This project established the curly top species/strains for which host plant resistance is needed as well as the time and areas when crops are at highest risk for infection.