Field studies were conducted in 1992 and 1993 in Hermiston, Oregon, to evaluate the efficacy of transgenic Bt potato (Newleaf®, which expresses the insecticidal protein Cry3Aa) and conventional insecticide spray programs against the important potato pest, Leptinotarsa decemlineata (Say), Colorado potato beetle (CPB), and their relative impact on non‐target arthropods in potato ecosystems. Results from the two years of field trials demonstrated that Newleaf potato plants were highly effective in suppressing populations of CPB, and provided better CPB control than weekly sprays of a microbial Bt‐based formulation containing Cry3Aa, bi‐weekly applications of permethrin, or early‐ and mid‐season applications of systemic insecticides (phorate and disulfoton). When compared with conventional potato plants not treated with any insecticides, the effective control of CPB by Newleaf potato plants or weekly sprays of a Bt‐based formulation did not significantly impact the abundance of beneficial predators or secondary potato pests. In contrast to Newleaf potato plants or microbial Bt formulations, however, bi‐weekly applications of permethrin significantly reduced the abundance of several major generalist predators such as spiders (Araneae), big‐eyed bugs (Geocorus sp.), damsel bugs (Nabid sp.), and minute pirate bugs (Orius sp.), and resulted in significant increases in the abundance of green peach aphid (GPA), Myzus persicae (Sulzer) – vector of viral diseases, on the treated potato plots. While systemic insecticides appeared to have reduced the abundance of some plant sap‐feeding insects such as GPA, lygus bugs, and leafhoppers, early and mid‐season applications of these insecticides had no significant impact on populations of the major beneficial predators. Thus, transgenic Bt potato, Bt‐based microbial formulations and systemic insecticides appeared to be compatible with the development of integrated pest management (IPM) against other potato pests such as GPA because these CPB control measures have little impact on major natural enemies. In contrast, the broad‐spectrum pyrethroid insecticide (permethrin) is less compatible with IPM programs against GPA and the potato leafroll viral disease.

The potato psyllid, Bactericera cockerelli (Šulc), is a major pest of potato (Solanales: Solanaceae) as a vector of ‘Candidatus Liberibacter solanacearum’ (Lso). Bactericera cockerelli colonizes potato from noncrop host plants, yet we do not yet know which noncrop species are the primary sources of Lso-infected psyllids. The perennial weed, Physalis longifolia Nutt., is a high-quality host for B. cockerelli and Lso under laboratory conditions but has been overlooked in recent field studies as a source of Lso-infected psyllids. Our current study had four objectives: 1) determine whether P. longifolia is abundant in potato-growing regions of Washington and Idaho, 2) determine whether stands of P. longifolia harbor B. cockerelli and Lso, 3) identify the psyllid haplotypes occurring on P. longifolia, and 4) use molecular gut content analysis to infer which plant species the psyllids had previously fed upon prior to their capture from P. longifolia. Online herbaria and field searches revealed that P. longifolia is abundant in western Idaho and is present at low densities in the Columbia Basin of Washington. Over 200 psyllids were collected from P. longifolia stands in 2018 and 2019, confirming that B. cockerelli colonizes stands of this plant. Gut content analysis indicated that a proportion of B. cockerelli collected from P. longifolia had arrived there from potato. Confirmation that P. longifolia is abundant in certain potato-growing regions of the Pacific Northwest, and that B. cockerelli readily uses this plant, could improve models to predict the risk of future psyllid and Lso outbreaks.