Avoidance of an electric field by insects: Fundamental biological phenomenon for an electrostatic pest-exclusion strategy

Using electric fields to control insects: current applications and future directions

Chemical-based interventions are mostly used to control insects that are harmful to human health and agriculture or that simply cause a nuisance. An overreliance on these insecticides however raises concerns for the environment, human health, and the development of resistance, not only in the target species. As such, there is a critical need for the development of novel nonchemical technologies to control insects. Electrocution traps using UV light as an attractant are one classical nonchemical approach to insect control but lack the specificity necessary to target only pest insects and to avoid harmless or beneficial species. Here we review the fundamental physics behind electric fields (EFs) and place them in context with electromagnetic fields more broadly. We then focus on how novel uses of strong EFs, some of which are being piloted in the field and laboratory, have the potential to repel, capture, or kill (electrocute) insects without the negative side effects of other classical approaches. As EF-insect science remains in its infancy, we provide recommendations for future areas of research in EF-insect science.

Turkestan Cockroaches Avoid Entering a Static Electric Field upon Perceiving an Attractive Force Applied to Antennae Inserted into the Field

This study analysed the mechanism of avoidance behaviour by adult Turkestan cockroaches (Shelfordella lateralis Walker) in response to a static electric field (S-EF) formed in the space between a negatively charged polyvinyl chloride-insulated iron plate (N-PIP) and a grounded metal net (G-MN). The negative surface charge supplied to the iron plate by a voltage generator caused the G-MN to polarise positively via electrostatic induction. In the S-EF, the negative charge of the N-PIP created a repulsive force that pushed free electrons in the field toward the ground via the G-MN. When insects released in the space surrounded by the S-EF inserted their antennae into the S-EF, they pulled them back reflexively and moved backward. The analysis indicated that an electric current flowed transiently toward the ground when an insect inserted its antennae into the S-EF. The insect became positively charged via this discharge and was attracted to the opposite pole (N-PIP). In response to this attractive force, the insect pulled its antennae back quickly. The positive electrification caused by the removal of free electrons from the antenna tip triggered the avoidance behaviour.

Selective Arcing Electrostatically Eradicates Rice Weevils in Rice Grains

Simple Summary

Rice stored in warehouses is frequently attacked by rice weevils, which must therefore be controlled. We developed an electrostatic method as an alternative to pesticides. An arc discharge exposer (ADE) kills insects entering an electric field. The apparatus has pairs of identical metal plates, one of which is linked to a voltage generator for negative charging, the other is grounded. A −7 kV electric field forms between the two plates. When an insect enters the electric field it is arced by the charged plate and killed. We combined this method with a technique that lures insects hiding in rice grains. When a vessel containing rice and insects was rotated and then returned to the initial position, the weevils climbed up the vessel walls and entered the ADE. Dead insects were collected to minimize rice contamination. This method efficiently killed pests in stored rice.

Abstract

We developed an arc discharge exposer (ADE) that kills rice weevils nesting in dried rice. The ADE features multiple identical metal plates, half of these are linked to a voltage generator and the others are grounded. The plates were arrayed in parallel and an electric field formed between them. Any insect entering the field was arced from the negatively charged plate and killed. The ADE was placed on a vessel containing pest-infested rice grains; the insects were lured out of the grains by mechanically vibrating the vessel. When rice grains move, insects tend to climb upward, thus, the weevils were effectively removed. Our electrostatic apparatus is easy to construct and could be used to control pests in stored rice.

Body Water-Mediated Conductivity Actualizes the Insect-Control Functions of Electric Fields in Houseflies

Simple Summary

The attractive forces generated in a static electric field, as well as corona and arc discharges generated in a dynamic electric field, are practical approaches for trapping and killing insects that enter the electric field. These electrostatic methods are realized by the conductive nature of the insect body. Thus, this work examined the role of body water on the conduction of electricity in the insect body. Adult houseflies (Musca domestica) were subjected to dehydration, rehydration, refrigeration, and freezing and thawing. These insects were then placed in static and dynamic electric fields to examine whether the release of negative charges from the insect caused attraction in the static field, as well as whether the fly was heated or dismembered when electricity passed through its body in a dynamic field. There was no current in the bodies of dehydrated and frozen flies; hence, there was no attractive force or discharge exposure. In the remaining insects, the results were identical to those in the control insects. Therefore, the conduction of electricity in the insect’s body water enables the insect-control effects of the electric fields.

Abstract

In the present study, the relationship between body water loss and conductivity was examined in adult houseflies (Musca domestica). The events an insect experiences in an electric field are caused by the conductive nature of the insect body (i.e., movement of electricity within or its release from the insect). After houseflies were dehydrated, rehydrated, refrigerated, and frozen and thawed, they were placed in static and dynamic electric fields. Untreated houseflies were deprived of their free electrons to become positively charged and then attracted to the insulated negative pole in the static electric field and were exposed to corona and arc discharge from non-insulated negative pole in the dynamic electric field. There was no current in the bodies of dehydrated and frozen flies; hence, there was no attractive force or discharge exposure. In the remaining insects, the results were identical to those in the untreated control insects. These results indicated that the reduction of body water conductivity inhibited the release of electricity from the body in the static electric field and the discharge-mediated current flow through the body in the dynamic electric field. The insect was affected by the electric fields because of its conductivity mediated by body water.

Insect Physical Control: Electric Field-Based Pest Management Approach

The Special Issue ‘Insect physical control: electric field-based pest management approach’ was launched to showcase valuable new research on pest control using applied electrostatic engineering. Some phenomena generated in static and dynamic electric fields can be used to build new devices to capture or kill target insects using an attractive force or a force striking insects entering an electric field. This research field is new, and there are few researchers currently working within it. Consequently, this editorial introduces the history and general principles of electric field generation. I then discuss future directions for this field.

High Voltage Electric Fields Have Potential to Create New Physical Pest Control Systems

An electric field is the space surrounding an electric charge, within which it is capable of exerting a perceptible force on another electric charge. Especially under high voltage, electric fields induce various electrostatic phenomena, some of which could be utilized to provide remarkable pest control measures. The main focus of the present study was to introduce an attractive force generated by a surface charge on an insulated electrified conductor, which was successfully used to construct an electric field screen that prevented airborne nuisances (spores, flying insects, pollen, and fine smoke) from entering the interiors of various facilities. Another focus was the disinclination of insects to enter the electric field, thus, giving the electric field screen the ability to repel insects. Charges accumulated on the surfaces of non-insulated conductors are mobile through discharge, based on their potential difference. Such arc discharge was strong enough to destroy insects that were exposed to it. Some precedent illustrative examples are cited to explain the principles of attraction, dielectrophoretic movement of spores, and discharge-mediated positive electrification of insects, and to discuss how electric fields are generated and used in electric field-based pest control strategies.

Analysis of Pole-Ascending-Descending Action by Insects Subjected to High Voltage Electric Fields

The present study was conducted to establish an electrostatic-based experimental system to enable new investigations of insect behavior. The instrument consists of an insulated conducting copper ring (ICR) linked to a direct current voltage generator to supply a negative charge to an ICR and a grounded aluminum pole (AP) passed vertically through the center of the horizontal ICR. An electric field was formed between the ICR and the AP. Rice weevil (Sitophilus oryzae) was selected as a model insect due to its habit of climbing erect poles. The electric field produced a force that could be imposed on the insect. In fact, the negative electricity (free electrons) was forced out of the insect to polarize its body positively. Eventually, the insect was attracted to the oppositely charged ICR. The force became weaker on the lower regions of the pole; the insects sensed the weaker force with their antennae, quickly stopped climbing, and retraced their steps. These behaviors led to a pole-ascending–descending action by the insect, which was highly reproducible and precisely corresponded to the changed expansion of the electric field. Other pole-climbing insects including the cigarette beetle (Lasioderma serricorne), which was shown to adopt the same behavior.