Comparison of electropenetrography waveform libraries for Nipaecoccus viridis (Hemiptera: Pseudococcidae) using different tethering materials and monitor settings

Authors: DEMARD, EMILIE - University Of Florida; Backus, Elaine; DIEPENBROCK, LAUREN - University Of Florida

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2025
Publication Date: 6/27/2025
Citation: Demard, E.P., Backus, E.A., Diepenbrock, L.M. 2025. Comparison of electropenetrography waveform libraries for Nipaecoccus viridis (Hemiptera: Pseudococcidae) using different tethering materials and monitor settings. Journal of Insect Science. 25(3). Article 23. https://doi.org/10.1093/jisesa/ieaf063.
DOI: https://doi.org/10.1093/jisesa/ieaf063

Interpretive Summary: The hibiscus mealybug, Nipaecoccus viridis, was first documented in Florida citrus orchards in 2019. Feeding damage causes fruit and leaf deformation due to cellular changes in citrus tissues. Field assays suggest that systemic insecticides can disrupt the phloem-feeding behavior of this pest. It is hypothesized that feeding damaged is caused by the insect’s saliva injected into phloem cells, but the mechanisms involved are poorly understood. The best way to study the cause of damage is to use AC-DC electropenetrography (EPG) to understand salivation, ingestion, and other behaviors. The objective of this study was to investigate the feeding of immature N. viridis on Volkamer lemon trees (Citrus volkameriana) using EPG. Because preliminary recordings failed to distinguish phloem salivation from phloem ingestion, the effects of three tethering materials to improve waveform details were tested. In addition, a combination of three different amplifier sensitivities and voltages applied to the plant were compared to create a waveform library. The best-quality signal was obtained with the thick gold wire (25 µm diameter) using the loop method of wiring plus amplifier sensitivity of 1010 Ohms. Biological interpretations of waveforms are discussed in light of fruit and leaf distortion. Results from this study will allow future work to compare effectiveness of insecticides to prevent such damage.

Technical Abstract: The hibiscus mealybug, Nipaecoccus viridis (Newstead) (Hemiptera: Pseudococcidae) is a phloem-feeding pest that was first documented in Florida citrus orchards in 2019. Feeding damage causes fruit and leaf deformation due to cellular changes in host plant tissues. Field assays suggest that systemic insecticides can disrupt the probing behavior of this phloem feeder. However, the mechanisms involved are poorly understood. The objective of this study was to investigate the feeding interactions of second-to-third instar N. viridis on Volkamer lemon trees (Citrus volkameriana) using AC-DC Electropenetrography (EPG). Because preliminary recordings failed to distinguish phloem salivation from phloem ingestion, the effects of three tethering materials to improve waveform resolution were tested: thick gold wire (25 µm diameter), fine gold wire (12.5 µm diameter), and Wollaston platinum wire (2.5 µm diameter). In addition, a combination of three different input resistances (Ri) (amplifier sensitivities) and substrate voltages; 109 O with 250 mV; 1010 O with 100 mV; and 1013O with 0 mV were compared to create a waveform library. The best-quality signal was obtained with the thick gold wire (25 µm diameter) at Ri 1010 O using the loop method of wiring. Wollaston platinum wire impeded nymphal movement, causing increased non-probing duration and increased time from the start of the recording to the first phloem salivation. Biological interpretations of waveforms are discussed in light of fruit and leaf distortion. Results from this study will allow future work to compare effectiveness of insecticides to prevent such damage.