Plant pathogenic bacteria may influence vector behavior by inducing physiological changes in host plants, with implications for their spread. Here, we studied the effects of maize bushy stunt phytoplasma (MBSP) on the host selection behavior of the leafhopper vector, Dalbulus maidis (DeLong and Wolcott). Choice assays contrasting leaves of healthy (mock-inoculated) vs. infected maize (Zea mays L.) were conducted during the asymptomatic and symptomatic phases of plant infection, with leafhopper males or females previously exposed to infected plants (bacteriliferous insects) or not. In each assay, 40 adults were released in choice arenas where only the leaves of two plants from each treatment were offered and visible, and the insects landed on the leaves were counted 1, 2, 3, 5, 7, 9, 11 and 23 h after release. During the asymptomatic phase of plant infection, an effect was observed only on bacteriliferous females, who preferred leaves of healthy plants 5 h after release or later. The symptomatic phase triggered a pull–push effect on non-bacteriliferous females, who were first attracted to symptomatic leaves but hours later moved to healthy leaves. Non-bacteriliferous males initially preferred symptomatic leaves (up to 5 h after release) and later became equally distributed between treatments. Bacteriliferous males and females initially did not discriminate between healthy and symptomatic leaves, but only the females tended to move to healthy leaves 9 h after release. Oviposition was drastically reduced on symptomatic leaves. The changes in vector behavior induced by MBSP favor its primary spread, since bacteriliferous females prefer healthy leaves at early (asymptomatic) stages of the crop. At later stages, secondary spread may be favored because non-bacteriliferous females are initially attracted to infected (symptomatic) leaves, allowing pathogen acquisition and subsequent transmission as they move to healthy plants.

Citrus huanglongbing (HLB) represents a major threat to citriculture due to its rapid spread, difficulty of control, severe yield losses, and substantial increases in production costs in HLB-affected orchards. Successful management depends on detailed knowledge of the epidemiology of this disease, which is associated with phloem-limited bacteria of the genus Candidatus Liberibacter that are transmitted by phloem sap-feeding insects known as psyllids (Hemiptera: Psylloidea). Candidatus L. asiaticus (CLas) and the Asian citrus psyllid Diaphorina citri Kuwayama are the major etiological agent and vector, respectively, in the Americas and Asia. This review provides up-to-date information on the relationships of psyllid vectors with Ca. Liberibacter spp. associated with HLB, with emphasis on D. citri and CLas. Knowledge of the transmission mechanisms of these bacteria, as well as aspects of the biology, ecology, and behavior of the vector in relation to the environment, is essential to gain understanding of the HLB epidemics. Such knowledge provides a basis for developing innovative control methods and establishing sustainable management strategies for HLB.