Plant infection and nutrition affect host preference behavior of Asian citrus psyllid: Laboratory and field experiments

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), is the vector of the bacterial pathogen, ‘Candidatus Liberibacter asiaticus’ (Las), which is the putative causal agent of huanglongbing (HLB) in citrus.  Las infection induces the release of a specific volatile (methyl salicylate) that attracts ACP. In this study, we investigated how infection status of plants (both symptomatic and asymptomatic) affects ACP host acceptance. We also investigated the effect of foliar nutrient applications, which are currently used to reduce HLB disease symptoms and increase yield production of Las-infected citrus, on ACP behavior.

In laboratory bioassays, ACP preferentially settled on infected citrus plants over uninfected controls, but this preference was greater when the infected plants were asymptomatic as compared with those showing symptoms of HLB. However, the symptomatic citrus plants that received supplemental foliar nutrient sprays were as attractive to ACP as asymptomatic trees that did not receive nutritional supplements.

In an experimental field with infected and uninfected citrus resets, we performed seasonal monitoring of ACP to determine the effect of nutritional sprays and Las infection on ACP population densities under field conditions. Thus far, we have not observed an effect of nutritional supplements on ACP settling behavior in the field as was observed in the lab. However, we did observe significantly higher ACP densities on infected compared with uninfected trees in the field, mirroring the laboratory results.