Formosan Subterranean Termites Re-Found in Southern California – PCT


Editor’s note: Jason and Lowell Boone, Better Off Dead Services (BODS), Riverside, California, discovered a Formosan underground termite infestation in a house in Canyon Lake, Riverside County, California in June PCT article). The infestation was confirmed by Professor of Entomology at the University of California-Riverside Dr. Chow-Yang Lee. Lee, along with co-authors Shu-Ping Tseng and Dong-Hwan Choe recently reported these results in the. released Journal of Economic Entomology. Here is a summary of their findings.

The underground termite of Formosa, Coptotermes formosanus, is one of the world’s most invasive termite pest species (Rust and Su 2012, Global Invasive Species Database 2021). Said to be native to southern China and Taiwan, this species has spread to other parts of the world, including the United States. Some of the earliest records of Formosa underground termites in the United States were found in Oahu, Hawaii, in 1957 in Charleston (SC), and in 1966 in New Orleans (LA) in Hawaii, Texas, Florida, North Carolina, Georgia, and Mississippi.

The subterranean Formosa termite was first discovered in La Mesa, San Diego County, California in 1992 (Atkinson et al. 1993). The original colony was baited (Haagsma et al. 1995), but more recent infestations were found and also baited, fumigated or corrected soil treatment (Rust et al. 1998). However, the program was discontinued in 1997 due to a lack of funds. In 2018, a pest exterminator found another infestation of the underground Formosa termite at La Mesa, about 0.3 miles from the location in 1992, and proceeded to treat the termite colony.

In June 2020, BODS Pest Control found an active C. formosanus infestation in a house in Canyon Lake. This place is about 65 miles north of La Mesa (illustration 1). Swarms of termites were found indoors and significant damage was found to the wall panels, exterior walls and bathroom floor on the 2nd floor.

The termites were collected from the infested area, soldier termites were examined under the microscope and identified as C. formosanus (Figure 2). They were also compared to the La Mesa samples (previously collected by Dr. Michael Rust, University of California Riverside). DNA techniques were used to determine the genetic differences between the three colonies collected. The genetic sequences of 3 colonies were also compared with the genetic sequences of the Formosa underground termite samples from other parts of the world available in GenBank.

The results showed that both La Mesa colonies (1992 and 2018) were identical but different from the Canyon Lake colony. The La Mesa colonies were genetically similar to those found in Asia, while the Canyon Lake colony resembled samples previously collected in Mississippi, Hawaii, Louisiana, Florida, and Georgia. In short, the La Mesa colonies were not related to the Canyon Lake colony, suggesting the latter was from a separate introduction.

How widespread the infestation is in Canyon Lake is currently unknown. Judging by the indoor swarms in late May and early June over the past eight years, it is possible that C. formosanus has settled near the infested premises. The abundance of trees and plants, coupled with ample irrigation in Canyon Lake, could aid its potential expansion and spread. Further sampling of the surrounding properties is required to determine the occurrence of Formosa underground termites in Canyon Lake.

Shu-Ping Tseng, Dong-Hwan Choe and Chow-Yang Lee are Postdocs, Associate Cooperative Extension Specialist and Professor & Endowment Chair of Urban Entomology at the University of California, Riverside. Siavash Taravati is Urban IPM Advisor at UCANR (Los Angeles Office).


Atkinson, TH, MK Rust, and JL Smith. 1993. The subterranean formosa termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), was established in California. Pan-Pac. Entomol. 69: 111-113.

Global Invasive Species Database (2021) Species profile: Coptotermes formosanus. Downloaded from on 04/26/2021.

Haagsma, K., TH Atkinson, MK Rust, D. Kellum, and DA Reierson. 1995. Formosa underground termites founded in California. Caliph. Agrarian. 49: 30-33.

Rust, MK and NY Su. 2012. Dealing with social insects of urban importance. Annu. Rev. Entomol. 57: 355-375.

Rust, MK, DA Reierson, E. Paine, D. Kellum, and K. Haagsma. 1998. Gluttonous Formosa underground termites exist in California. Caliph. Agrarian. 52: 34-37.