Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2011
Publication Date: 2/28/2012
Citation: Youngnam, Y., Backus, E.A., Serikawa, R., Stelinski, L. 2012. Correlation of an electrical penetration graph waveform with walking by Asian citrus psyllid, Diaphorina citri Kuwayama. Florida Entomologist. 94:1084-1087. Interpretive Summary: Citrus growers in Florida extensively use insecticides to control the Asian citrus psyllid (ACP). Electrical penetration graph (EPG) monitors are being used to determine the effect of insecticides on psyllid feeding behavior. The present study defined two new EPG waveforms recorded when ACP was either walking (NP) or standing still (Z) before the insect began feeding. NP was correlated with electrical contact caused by textured structures on the psyllid tarsus that were imaged using SEM. Covering the tarsi with smooth, clear nail polish abolished the electrical conductance that caused voltage fluctuations in NP. Despite walking by nail polish-treated insects, only the flat Z waveform (true baseline) was displayed. The walking waveform will be useful for EPG studies of insecticide effects because it will identify whether an insect becomes paralyzed before dying.
Technical Abstract: Electrical penetration graph (EPG) monitoring is being used to study how feeding behavior of the Asian citrus psyllid (ACP) (Diaphorina citri Kuwayama) changes in response to insecticides, in an effort to improve the efficacy of widespread insecticide treatments against the insect in Florida citrus. The present study characterized and correlated two EPG waveforms, NP and Z, recorded when ACP was walking/labial dabbing or standing still, respectively, prior to insertion of the stylets into the plant to begin feeding. The variable-voltage NP waveform was correlated with electrical contact caused by structures on the psyllid tarsus, such as tarsal claws or texture of the arolium (imaged using SEM). This conclusion is supported because covering the tarsi with smooth, clear nail polish abolished the electrical conductance. Despite walking by nail polish-treated insects, only the flat Z waveform (true baseline) was displayed. This is the first time (cited in the literature) that a walking waveform has been detected for a sternorrhynchan hemipteran using the Giga8 EPG monitor. The walking waveform will be useful for EPG studies of insecticide effects because it will identify whether an insect becomes paralyzed from insecticide effects.