Electropenetrography: A New Diagnostic Technology for Study of Feeding Behavior of Piercing-Sucking Insects

Abstract

Studying the feeding, plant damage, and transmission (i.e., acquisition, retention, and inoculation) of plant pathogens caused by hemipteran insect pests has always been a challenge. This is primarily because their specialized, piercing-sucking mouthparts, the stylets, perform probing/penetrating action into opaque plant tissues in which the stylets cannot be directly visualized. This challenge was overcome by a technological revolution over 50 years ago; the invention of electropenetrography, or electrical penetration graph (EPG) monitoring, the most rigorous method to identify feeding behaviors of hemipteran crop pests. Today, EPG is used in three main areas for the development of novel integrated pest management (IPM) tactics for hemipteran pests. Firstly, in cases where the fundamental mechanisms of feeding damage or transmission of a plant pathogen are unknown, EPG is instrumental in identifying such mechanisms. Secondly, once the feeding-related causes of damage or pathogen transmission are understood, EPG can be used to demonstrate the effects of insecticides, antifeedants, or other chemical compounds on specific feeding behaviors responsible for the damage or transmission. Thirdly, EPG can similarly identify the effects of resistant vs. susceptible varieties of crop plants, including transgenic plants genetically engineered to express biopesticides. The purpose of this paper is to review: (1) principles and history of EPG, especially development of the new and improved, third-generation AC-DC monitor, (2) what waveforms and types of information can be gained via EPG, using aphid pests as a model system, and (3) how EPG can be applied to the special needs of Taiwanese agriculture, especially for some species of aphids of economic significance in Taiwan. For the first time in print, our review describes and discusses in details the information of all three types of EPG monitors used for researches on aphids.