Curly Top Viruses and Phytoplasmas in Sugar Beets, Common Beans, and Beet Leafhoppers Along with Vector Population Dynamics in Southern Idaho

Abstract

Beet curly top in sugar beet and common bean is a major yield limiting factor 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. In one desert area (Elmore Co.), BLH populations began increasing in May and 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 sequence, two haplotypes dominated the BLH population. Both years, BCTV strains Worland and Colorado were the primary strains in BLH and plant samples. The California/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.