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.

T929I and K1774N mutation pair and M918L single mutation identified in the voltage-gated sodium channel gene of pyrethroid-resistant Thrips tabaci (Thysanoptera: Thripidae) in Japan.

Pyrethroid-resistance in onion thrips, Thrips tabaci, has been reported in many countries including Japan. Identifying factors of the resistance is important to correctly monitoring the resistance in field populations. To identify pyrethroid-resistance related genes in T. tabaci in Japan, we performed RNA-Seq analysis of seven T. tabaci strains including two pyrethroid-resistant and five pyrethroid-susceptible strains. We identified a pair of single point mutations, T929I and K1774N, introducing two amino acid mutations, in the voltage-gated sodium channel gene, a pyrethroid target gene, in the two resistant strains. The K1774N is a newly identified mutation located in the fourth repeat domain of the sodium channel. Genotyping analysis of field-collected populations showed that most of the T. tabaci individuals in resistant populations carried the mutation pair, indicating that the mutation pair is closely associated with pyrethroid-resistance in Japan. Another resistance-related mutation, M918L, was also identified in part of the resistant populations. Most of the individuals with the mutation pair were arrhenotokous while all individuals with the M918L single mutation were thelytokous. The result of differentially expressed gene analysis revealed a small number of up-regulated detoxification genes in each resistant strain which might be involved in resistance to pyrethroid. However, no up-regulated detoxification genes common to the two resistant strains were detected. Our results indicate that the mutation pair in the sodium channel gene is the most important target for monitoring pyrethroid-resistance in T. tabaci, and that pyrethroid-resistant arrhenotokous individuals with the mutation pair are likely to be widely distributed in Japan.

Release of the Flightless Strain of Harmonia axyridis (Coleoptera: Coccinellidae) Against Two Aphid Species on Komatsuna (Brassica rapa var. perviridis) in Open Fields.

Myzus persicae (Sulzer) (Hemiptera: Aphididae) and Lipaphis erysimi (Kaltenbach) are important pests of Brassica leafy vegetables, especially in Japan, the United States, and India. In Japan, because most of the nonheading Brassica vegetables are considered minor crops, the number of commercially available pesticides against these aphids is limited. Here, we evaluated the effect of releasing adults of a flightless strain of the multicolored Asian ladybird, Harmonia axyridis Pallas, on these aphid species on a nonheading Brassica cultivar in open fields. Three weeks after, ladybirds were released onto aphid-infested plants at a rate of two adults per m2, only 4-12% equal numbers of aphids were found on plants with ladybirds as without ladybirds in all three trials. The result indicates that H. axyridis adults are the effective biocontrol agents against aphids on the plants.