Identification of three new 'Candidatus Liberibacter solanacearum' haplotypes in four psyllid species (Hemiptera: Psylloidea).

Eleven haplotypes of the bacterium, 'Candidatus Liberibacter solanacearum', have been identified worldwide, several of which infect important agricultural crops. In the United States, haplotypes A and B are associated with yield and quality losses in potato, tomato, and other crops of the Solanaceae. Both haplotypes are vectored by potato psyllid, Bactericera cockerelli. Recently, a third haplotype, designated F, was identified in southern Oregon potato fields. To identify the vector of this haplotype, psyllids of multiple species were collected from yellow sticky cards placed near potato fields during two growing seasons. Over 2700 specimens were tested for 'Ca. L. solanacearum' by polymerase chain reaction. Forty-seven psyllids harbored the bacterium. The infected specimens comprised four psyllid species in two families, Aphalaridae and Triozidae (Hemiptera: Psylloidea). Nucleic acid and/or amino acid sequence analysis of the 'Ca. L. solanacearum' 16S ribosomal RNA, 50S ribosomal proteins L10/L12, and outer membrane protein identified three new haplotypes of the bacterium, designated as Aph1, Aph2 and Aph3, including two variants of Aph2 (Aph2a and Aph2b). The impact of these new haplotypes on solanaceous or other crops is not known. The vector of 'Ca. L. solanacearum' haplotype F was not detected in this study.

Baseline Susceptibility of Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) to Commonly Used Insecticides in the Columbia Basin.

Colorado potato beetle (CPB), Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), is one of the most challenging pests of potato, Solanum tuberosum L., largely due to its propensity to develop insecticide resistance. Historically, L. decemlineata has rapidly evolved resistance to all major classes of synthetic insecticides, particularly in the eastern United States. However, in the U.S. Pacific Northwest, there have thus far been no confirmed reports of insecticide resistance despite anecdotal accounts of control failure. Hence, the objective of this study was to develop baseline data on the susceptibility of L. decemlineata in the Columbia Basin to abamectin, imidacloprid, and spinetoram, three insecticides commonly used to manage this insect. In 2018 and 2019, baseline susceptibility of four L. decemlineata populations, three from the Columbia Basin and one from Wisconsin (used as a resistant reference), was examined using topical LD50 bioassays. In general, L. decemlineata populations in the Columbia Basin exhibited relatively high sensitivity to imidacloprid, but variable sensitivity to abamectin and spinetoram among sites and years. Although small sample sizes hindered estimation of statistically significant LD50 values, results suggest that L. decemlineata in the Columbia Basin are beginning to develop levels of insensitivity to spinetoram, and possibly abamectin that are comparable to insecticide-resistant populations in Wisconsin. This preliminary examination of geographic variation in sensitivity to commonly used insecticides reinforces the value of rotating insecticide modes of action and suggests the need for continued monitoring for the development of insecticide resistance throughout the U.S. Pacific Northwest.