Colony Suppression and Possible Colony Elimination of the Subterranean Termites Coptotermes formosanus and Reticulitermes speratus by Discontinuous Soil Treatment Using a Diluent of Fipronil Suspension Concentrate.

Shuji Itakura,Johji Ohdake,Takashi Takino,Kiwamu Umezawa

doi:10.3390/insects12040334

Abstract

Simple SummaryTermites play an important role in maintaining ecosystems, but they are also pests, exerting major economic impacts. Among the over 3000 known termite species, Coptotermes species and Reticulitermes species are the most common pest species. As one of the primary methods for controlling these subterranean termites, liquid termiticide is applied to the soil under and next to the building foundation to create a continuous chemical barrier. Nonrepellent slow-acting liquid termiticides, such as fipronil and imidacloprid, are used as the active ingredients in termite soil treatments. In the present study, to minimize the use of insecticides, a discontinuous soil treatment using fipronil was applied against subterranean termites, namely Coptotermes formosanus and Reticulitermes speratus, instead of the traditional continuous chemical barrier of termiticides. C. formosanus and R. speratus colonies were subjected to discontinuous soil treatments with fipronil and were strongly affected by the treatment at the colony level, resulting in colony suppression and possible colony elimination. Termite activity in the treated colony of C. formosanus was not found for more than two years, while that of R. speratus was not detected for three years.We assessed the efficacy of a discontinuous soil treatment using a diluent of fipronil suspension concentrate in controlling colonies of Coptotermes formosanus and Reticulitermes speratus. In-ground monitoring stations were installed at Isogi Park and Kindai University, and individual termites inhabiting the stations were collected for four or six years to determine the numbers and locations of colonies present in test areas before and after the discontinuous soil treatment. Microsatellite genotyping indicated that two C. formosanus and two R. speratus colonies in the test area at Isogi Park and five R. speratus colonies in the test area at Kindai University were active and that their territories fluctuated every year. One of the two C. formosanus colonies at Isogi Park and one of the five R. speratus colonies at Kindai University were subjected to discontinuous soil treatments with fipronil and were strongly affected by the treatment at the colony level, resulting in the suppression and possible elimination of colonies. Termite activity of the fipronil-treated colony of C. formosanus was detected within one week after the discontinuous soil treatment and was not found for more than two years (28 months), while termite activity of the fipronil-treated colony of R. speratus was detected within four days and three weeks after the discontinuous soil treatment and was not detected thereafter for three years. Fipronil residue analysis showed that workers of C. formosanus moved at least 28 m and that workers of R. speratus moved 6 m from the treated soil locations for up to three weeks.

Highlights

Termites play an important role in maintaining ecosystems, with effects on the physical, chemical and biological properties of soils, soil microbiology, and plant growth [1,2,3]; they are pests, exerting great economic impact worldwide
14 cohorts from two populations of R. speratus (Figure 7) and 18 cohorts from two populations of C. formosanus in Isogi Park (Figure 8) (of which 9 cohorts had been found at the time of discontinuous soil treatment (Table 1)) and 34 cohorts of R. speratus in Kindai
Differences in the allele sizes of the two colonies, A and B, analyzed by microsatellite genotyping, showed that two simple family colonies (A and B) would be found by different pairs of kings and queens derived from winged alates in Isogi Park (Supplementary Table S4, 212 bp in locus Cf4-4, 285 bp in locus Cf4-9A, 221 bp in locus Cf8-4, and 265 bp in locus Cf10-5)

Summary

Introduction

Termites play an important role in maintaining ecosystems, with effects on the physical, chemical and biological properties of soils, soil microbiology, and plant growth [1,2,3]; they are pests, exerting great economic impact worldwide. Nonrepellent slow-acting liquid termiticides have become a popular alternative to fast-acting repellent pyrethroids as the active ingredients in termite soil treatments [7]. The main active ingredients of nonrepellent slow-acting termiticides are fipronil, imidacloprid, chlorfenapyr, and chlorantraniliprole [8,9,10,11]. The effectiveness of these nonrepellent slow-acting termiticides against subterranean termites has been field-validated using the conventional soil treatment method in which a continuous exterior barrier of nonrepellent soil termiticides is established in soil on the structure’s exterior foundation walls. All 11 of the fipronil-treated colonies of Reticulitermes flavipes (Kollar) disappeared within 90 days of treatment and were not found again [8]. In the majority (83.3%) of the 12 chlorantraniprole-treated colonies of R. flavipes, termite activity was no longer detected within one or two months after the soil treatment and thereafter for two years [13]

Methods

Results

Conclusion