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Feeding behaviors of the redbanded stink bug, Piezodorus guildinii (Westwood), on vegetative (stem and leaflet) and reproductive (pod) tissues of soybean, Glycine max (L.), were recorded using an AC-DC electropenetrograph (EPG) apparatus. Eight different probing waveforms were characterized and defined: Pg1a,

In this article, we review and discuss the potential use of EPG (electropenetrography) as a powerful tool to unveil the feeding process of phytophagous stink bugs (pentatomids). These bugs are relatively big and vigorous, which presents a problem during wiring (i.e., attachment of the gold wire on the bug's pronotum) for use in EPG. Once this challenge was overcome, using the sand paper-and-wire technique, several species have been studied using EPG, yielding waveforms that, coupled with histological studies, revealed the ingestion sites on different host plants. These sites include vascular tissues (xylem and phloem), parenchyma tissue, and seed endosperm. Stink bugs usually feed by secreting a gelling saliva to create a salivary sheath that surrounds the stylets and anchors/supports/lubricates them. However, using the cell rupture feeding strategy and the tactic of combined laceration (mechanical movements of the stylets) and maceration (action of chemical enzymes) breaks the plant cells enabling ingestion. The number of ingestion events and their duration is variable according to the feeding site. Waveforms generated have typical patterns according to the feeding site. Recent studies with several species of stink bugs have started to demonstrate the potential of EPG as a tool to unveil their feeding behavior. This may also be useful in the applied field of stink bug management, such as the development and screening of resistant genotypes and the action of chemical insecticides affecting their feeding and survivorship.

Stink bugs (Hemiptera: Heteroptera: Pentatomidae) are in general robust and restless insects, which makes them difficult to wire for electropenetrograph (EPG) studies. In addition, cuticular lipids may reduce wire effectiveness, and their removal could improve success of wiring. We compared wiring effectiveness for three species of stink bugs, differing in walking behaviour and degree of cuticular waxiness, that is, Piezodorus guildinii (Westwood), Nezara viridula (L.), and Loxa deducta (Walker). Results indicated that removal of cuticular lipids by mechanical abrasion (via sanding) greatly improved attachment success with gold wire. Our hypothesis that heavier and bigger bugs would lose the wire attachment more quickly than lighter and smaller bugs was not confirmed, regardless of the sanding. In contrast, our hypothesis that greater movement of a bug would cause the wire to break more often was supported by extensive testing. Behaviour appears to be more relevant for successful wiring than body weight. We used the sanding and wiring technique to characterize and correlate direct current EPG waveforms for the large and restless stem-feeding stink bug Edessa meditabunda (Fabricius) on soybean plants. This marks the first published example of pentatomid EPG waveforms. Edessa meditabunda recordings on soybean stems generated eight types of waveforms in three phases and two families, named as follows: non-probing = Np and Z; pathway phase = Em1; X wave phase = X; ingestion phase, family I = Em2 and Em3; ingestion phase, family N = Em4 and Em5. These eight were described based on their frequencies, relative amplitudes, and level voltages. Histological studies of stylets within salivary sheaths correlated the Em1, Em2, and Em3 waveforms with specific penetration sites. The waveform with the longest duration when feeding was Em2, representing xylem sap ingestion; in addition, waveform Em3 (always preceded by an X wave) was correlated with phloem sap ingestion.

Once abundant in the Americas, the southern green stink bug Nezara viridula (L.) has gradually declined in numbers. Until the 1990s, it was considered the main pest of major crops such as soybean, Glycine max (L.) Merrill, particularly in southern Brazil and southern USA, as well as Argentina, Uruguay, and other countries. In the past 15+ years, a dramatic population decrease was observed to the point of now being considered a secondary pest in these referred countries. In this article, we list and discuss possible reasons which explain the decline in N. viridula population in the Americas. These factors include the following: (1) the steady increase of herbicides used in no-tillage/multiple cropping systems affecting potential hosts such as weeds in crop fields and nearby natural vegetation; (2) the change in cultivation systems, mostly in the Neotropics, favoring other species more adapted to exploit crops in modern day agriculture; (3) competition among several species of stink bugs that colonize major crops; (4) the growing impact of several species of egg parasitoids, some of them laboratory reared and released in crop fields, and other natural enemies (parasitoids and predators); and (5) the impact of global climate change affecting its distribution and biology.

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The Neotropical brown-stink bug Euschistus heros (F.) (Hemiptera: Pentatomidae) is the most important pest damaging soybean in the Neotropics, the world largest production area. The alternating current–direct current (AC–DC) electropenetrography (EPG) technology was used to develop an EPG waveform library of adult females feeding on soybean (Glycine max (L.) Merr.) pods at different input resistor (Ri) levels. Thirteen waveform types/subtypes were identified and described. They were divided into non-probing (Z, Np, Dw1, and Dw2), and probing waveforms (Eh1, Eh2, Eh3, Eh4, and Eh5). Probing waveforms were grouped into three phases: 1) pathway (Eh1a, Eh1b, Eh1c, and Eh1w), 2) ingestion (Eh2, Eh3a, Eh3b, and Eh4), and 3) interruption (Eh5). Correlations between waveforms Eh1b, Eh1c, Eh2, Eh3, and Eh4 and stylets tip position and/or salivary sheath in the pod tissue were determined via histological studies. Non-probing waveforms, Z and Np were visually associated with the bug resting and walking on pod surface, respectively. Waveform Dw1 was correlated with egestion, and the ingestion of fluids (droplets) was proposed for Dw2. Eh1a and Eh1b corresponded to initial and deep stylet penetration through pod tissue, and secretion of a salivary sheath. In Eh1c, stylets penetrated the rigid cell layer of sclerenchyma, and during Eh1w they were withdrawn. Eh2 represents sustained xylem sap ingestion. Eh3a corresponded to lacerate and macerate cell rupture feeding behavior in seed endosperm, whereas Eh3b corresponded to ingestion of cellular contents. Eh4 represented short ingestion from an unknown site, and Eh5 represented short interruptions during xylem sap ingestion.