Nonconsumptive effects of the predator Hippodamia convergens reduce probing behavior of Diaphorina citri on Citrus sinensis

Abstract

Nonconsumptive effects (NCEs) impact predator–prey interactions when the presence of a predator affects behavior, physiology, or population dynamics of the prey species without resulting in consumption. NCEs are critical to understanding ecological interactions broadly and in an applied manner, when addressing the efficacy of biological control within agroecosystems. In this study, we explore the impact of cues from the predator, Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae), on the probing and feeding behavior of Diaphorina citri Kuwayama (Hemiptera: Psyllidae), the Asian citrus psyllid (ACP), which transmits the causal bacteria of Huanglongbing (HLB) disease of citrus (Rutaceae). Due to wide-spread HLB incidence and insecticide resistance, it has become critical to better understand the activity of biological control agents within the HLB–ACP pathosystem. Utilizing electropenetrography (EPG), we investigated the feeding behavior of ACP exposed to the predator H. convergens or exposed to the chemical trails H. convergens produce while foraging. Overall, ACP detected H. convergens cues and responded by avoiding probing, although the extent of this response varied depending on the type of cue perceived. When H. convergens was present in the leaf but unable to reach the psyllid, ACP were slower to initiate probing and spent less time overall on probing and feeding from the xylem. In contrast, when exposed to H. convergens foraging cues without the beetle present, ACP initiated probing quicker than when the beetle was present and had a shorter total probing time compared to the control, with no other parameters being affected. Interestingly, the H. convergens chemical trail extracts, at two dosages, did not significantly influence ACP probing and feeding, except for a lower proportion of salivation and ingestion events into the phloem at the lower test dose. Our results suggest ACP exhibits avoidance behaviors in response to H. convergens cues, leading to a reduction in feeding, which suggests the maintenance of agroecosystem health through preservation of insect community diversity may be overlooked as an additive factor in vector management.