Perceived benefits of insecticidal transgenic crops include reduced usage of broad-based insecticides, and therefore lower risk to non-target organisms. Numerous studies have documented low or no direct toxicity of Bacillus thuringiensis (Bt)-derived toxins against non-target organisms, but there has been less research on (a) effects of secondary pest infestations on Bt expressing in crops and (b) behavioural responses by predators feeding on host arthropods from Bt crops - both topics are investigated in this study. We quantified predation by the obligate spider mite predator Phytoseiulus persimilis of carmine spider mites (Tetranychus cinnabarinus), reared on Bt or non-Bt corn (Zea mays). Both no-choice and two-choice studies were conducted. In addition, we quantified toxin levels in corn leaves with/without spider mite infestation. Under no-choice conditions, P. persimilis consumed non-Bt spider mites at a faster rate than Bt spider mites. Under two-choice conditions, P. persimilis spent more time in the vicinity of non-Bt spider mites than near Bt spider mites. Corn infested with spider mites exhibited lower toxin levels than non-infested plants. These results suggest potentially complex interactions among non-target herbivores, their natural enemies and Bt crops. © 2014 Association of Applied Biologists.

Long-term, sustainable management of zebra chip disease of potato, caused by 'Candidatus Liberibacter solanacearum' (Lso) and vectored by potato psyllids (Bactericera cockerelli Sulc [Hemiptera: Triozidae]), requires development of cultivars resistant or tolerant to infection or capable of reducing spread or both. We examined the influence that five experimental breeding clones of potato had on potato psyllids and their ability to vector Lso. The ability of these potato clones to resist aphids (green peach aphids, Myzus persicae Sulzer [Hemiptera: Aphididae]) also was examined. Due to the importance of host chemistry on plant-insect interactions, levels of primary metabolites of amino acids and sugars, as well as secondary metabolites including polyphenolics, terpenoids, and alkaloids were compared between breeding clones and a commercial cultivar. Findings for compound levels then were associated with observed changes in host susceptibility to psyllids or aphids. Psyllids oviposited less on three breeding clones than Atlantic, but no significant effects of breeding clones on psyllid feeding or choice were observed. Aphid reproduction was reduced on two clones relative to Atlantic. A05379-211 had greater sugar levels and postpsyllid amino acid levels than Atlantic. Total alkaloid and phenolic levels were greater in all breeding clones than Atlantic. Total terpenoid levels were greater in PALB03016-3 and PALB03016-6 than Atlantic, which might explain, in part, the observed resistance to psyllid oviposition and aphid reproduction. Overall, these results suggest that increased levels of certain metabolites in breeding clones could affect psyllid and aphid reproduction.