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- Author: Mike Hsu
During summer swarming season, homeowners urged to check for signs of Formosan subterranean termite
In the lottery of troublesome termite infestations, “Roger,” a Rancho Santa Fe homeowner, hit the jackpot (a pseudonym is used to protect his privacy). In 2021, his house in San Diego County was identified as home to only the fourth documented colony of the Formosan subterranean termite (Coptotermes formosanus) in California.
“FST is one of the most destructive urban pests in the world,” said University of California, Riverside entomologist Chow-Yang Lee, affiliated with UC Agriculture and Natural Resources through the campus' Agricultural Experiment Station. “It's also the only termite species listed in the ‘100 of the World's Worst Invasive Alien Species.'”
Endemic to East Asia, this termite is now established in many tropical and subtropical regions, including across the American South. Annually, its infestation costs more than $4 billion in control measures and damage repairs of structures in the U.S.
FST was first discovered in California in La Mesa (San Diego County) in 1992, and it was rediscovered in that city in 2018. Another infestation was reported in Canyon Lake (Riverside County) in 2020. And then, the following year, Roger received his surprise.
“Imagine being in your kitchen looking at your drywall and it's totally normal and then the next day there's a four-inch hole there and you're like ‘What the heck is that? Who put their elbow into the drywall?'” he recalled.
FST colonies can reach millions of individuals
Roger hired a pest control company, Green Flash Pest Control, which sprayed a powerful liquid termiticide in the soil around the house. But the termites – workers, soldiers and winged “alates” – continued to appear. The company tried a second application of soil treatment. But, again, the termites kept popping up.
“We were deeply concerned about the potential damage these termites could cause to the home since these invasive termites are extremely destructive,” said Eric Veronick, director of operations at Green Flash. “Unfortunately, there isn't a whole lot of information available on the behavior and management of this termite in California.”
The company called upon Siavash Taravati, a UC Cooperative Extension urban Integrated Pest Management (IPM) advisor based in Riverside.
“Some colonies are aerial, meaning that they are formed above the ground with limited or no connection to the soil – in such cases, soil treatment using contact insecticides may not be very effective in managing these termites,” Taravati said. “Furthermore, contact insecticides usually kill a much smaller portion of the colony when compared to termite baits.”
To make matters worse, once FST is established in an area, there have been no records of successful eradication anywhere in the world, according to Taravati. He added that a major reason why the Formosan subterranean termite is so destructive is the enormous size of their colonies.
“Their colonies can reach millions of individuals, versus most native subterranean species that reach a few hundred thousand individual termites per colony,” Taravati explained.
This termite, through its sheer numbers, can turn the wood in a structure into a “spongy kind of cake,” in Taravati's words. More than 10 pounds of wood in a house can be eaten by a mature colony each month. The financial hit for a homeowner can be substantial, up to tens of thousands of dollars – not to mention the increased risks to safety.
“Anything from studs to rafters to door frames and window frames – everything is going to be compromised, if the termites are left unchecked. And then, as soon as we have a major stress on the building, let's say there's a big storm or an earthquake – there's a high risk of at least part of the building collapsing,” said Taravati, who also noted that, unlike California native subterranean termite species, FST can attack and kill live trees and plants.
“These termites can be a nightmare,” he said.
Summer is ‘swarming season' for FST
Since the Rancho Santa Fe case in 2021, four more colonies have been documented, in La Mesa again and also in Highland Park, Hollywood Hills and La Verne (the latter three in Los Angeles County). Taravati said it's possible that FST has been spreading via structural lumber or potted plants and soil.
And even if a colony appears to be eliminated at a certain locale, Taravati noted, there is always the chance that part of the colony survives or more colonies of termites already have been established in nearby locations, as a result of swarming termites from the originally infested property.
Although nominally “subterranean,” certain members of an FST colony grow wings and fly to nearby locations to establish new colonies. These winged alates are also called swarmers because of their behavior during the “swarming” season, when termites mate and reproduce.
For the Formosan subterranean termite, that swarming season in California is late May through early August, so now is the time for homeowners and building managers in southern and central California to keep an eye out for those winged termites.
“If you experience a termite swarm in your house, contact a pest management professional and keep some termite samples in a Ziploc bag in the event you need to send the samples to UC Riverside for morphological and DNA-based identifications,” said Lee, who added that it's a good idea to periodically check your structure for signs of infestation, such as wood damage or shelter tubes (mud tubes).
Lee said FST swarmers have a lighter colored body compared to the dark color of native subterranean termites and the orange-brown body of drywood termite swarmers (see this flyer for additional identification information).
Following an especially wet winter, there's a chance California could see more FST infestations, as this termite generally requires moist environments to thrive, Lee added. He recommends that concerned community members seek professional advice.
“Do not attempt to control an FST infestation by yourself,” Lee said. “This is not your typical native Californian subterranean termite species; they are highly destructive, and you want to intercept the problem with the right strategy before it's too late.”
Homeowner: ‘I owe them my house'
In Roger's case, Taravati enlisted the help of Lee and his UC colleague, Greg Kund. They made multiple visits to inspect the home and analyze the situation – going “above and beyond,” according to Roger.
At Lee's suggestion, they used a caulk gun to insert a gel-like experimental bait into the wall where the termites were coming out. Once spread and passed on to the other nestmates, the product – which contains a chitin synthesis inhibitor (a type of insect growth regulator) – interrupts the termites' development so they are unable to properly molt and replace the short-lived “workforce” of foragers and soldiers. The colony eventually collapses and is eliminated.
“Generally speaking, IGRs are much more effective, but they require more patience,” Taravati explained. “You're not going to see the results the next day, or two-three days. You're going to see the results in a few weeks – but when you see the results, it's massive.”
And that's exactly what Roger and Green Flash Pest Control saw.
“Soon after their bait application, the termites stopped emerging from the walls and that gave us and the homeowner a big sigh of relief,” Veronick said. “I appreciate their expertise and dedication in helping us get rid of this destructive pest."
Roger said he is immensely grateful to the UC team.
“They were fantastic; I owe them my house,” he said. “They were super gracious and helpful and responsive and – ultimately, the thing I care most about – they were effective; they fixed the problem. Here we are two years later and – knock on wood, or maybe I should knock on something else! – everything is good.”
Lee also credited Taravati for bringing his knowledge and “can-do” attitude to communities across Southern California.
“He is highly knowledgeable and always able to come up with feasible solutions,” Lee said. “We need good Cooperative Extension urban IPM advisors like Siavash who could provide good advice and bring solutions to the stakeholders, be they homeowners or pest management professionals.”
Taravati said community members need to maintain their vigilance and urges them to download and share the FST flyer that includes identification tips and contact information. He said they are always free to e-mail him with their concerns and photos of suspected FST – not only to help stop the spread of the pest but to expand scientific understanding.
“This termite is so new to California – even for us, as researchers. Despite being in La Mesa since the 1990s, it wasn't until 2020 when these termites were detected in other places, including Riverside and Los Angeles counties,” Taravati explained. “All of us need to learn more about this pest and closely monitor the behavior of this pest.”
- Author: Lauren Fordyce
What do Earth Day and Integrated Pest Management (IPM) have in common? They both seek to protect the beautiful planet we all share! IPM is an environmentally friendly way to manage pests, focusing on nonchemical control methods (cultural, physical, and biological) rather than relying solely on pesticides. The main goal is to reduce pests but to achieve that without harm to people, water, soil ecosystems, beneficial insects, and wildlife.
This Earth Day, see how you can use IPM to protect the environment. Here are some ideas:
Plant flowers
Flowering plants, especially those native to California, are not only beautiful but incredibly important for pest control! Natural enemies, also called beneficial insects or good bugs, feed on pollen and nectar from flowering plants. In addition, flowering plants provide them with a place to lay eggs and hide from predators. Natural enemies, which include lady beetles (ladybugs), lacewings, soldier beetles, assassin bugs, spiders, parasitic wasps, and even some mites, feed on pests in the garden and landscape. They can naturally control pest problems, reducing the need for pesticides.
You can protect and encourage natural enemies by avoiding the use of broad-spectrum pesticides that kill them, managing ants, and planting an array of flowering plants. Choose plants well adapted to your area and choose species or cultivars that bloom at different times of the year to provide natural enemies with food year-round.
Water wisely
Giving your plants enough water is essential for their survival, but ensuring they have enough and not too much can be very important for IPM too. When plants are water-stressed, they are often more susceptible to pests. When plants are overwatered, they can also be prone to more pests. It is a delicate balance but ensuring your plants get the water they require (which will vary by species or plant type) is a great way to minimize pests problems and promote healthy plants that can better tolerate pest feeding. Consider planting drought-tolerant plants that are less likely to experience water stress.
Understand pesticides
Certain pesticides can harm people, nontarget organisms, aquatic wildlife, and natural enemies when used improperly. It is important to understand when pesticides might be needed, and how to apply them in ways that minimize risks to people and the environment. Use less toxic pesticides whenever possible. Always read the product label for information on when and how to apply, which plants or pests you can apply for, and how much to use. Wear personal protective equipment (PPE) and take caution not to allow the pesticide to runoff or drift. Also, dispose of unused pesticide at a household hazardous waste disposal site. Enter your zip code here to find a location near you.
Use nonchemical tools
There are many, many ways to prevent and control pests without the use of pesticides. In IPM, we use a variety of tools to achieve this. Tools might include mulch, soil solarization, or garden hoes instead of herbicides for weed control; protective coverings, netting, screens, or weather-stripping to keep pests off plants and out of the home; or traps to control vertebrate pests like rats without the use of rodenticides. See any of the UC IPM Pest Notes to read what tools and nonchemical control methods work to manage indoor or outdoor pests.
Happy Earth Day!
This Saturday, April 15th, is the annual UC Davis Picnic Day event!
Stop by the UC Statewide IPM Program's booth from 9am to 3pm in the entomology building, Briggs Hall.
We'll have ladybugs (lady beetles) for you to take home, fun insect temporary tattoos for all ages, preserved insects on display, and a “good bug” scavenger hunt! You can also find information on various pests as we will showcase our publications, online tools, and resources.
Visit us with your pest-related questions and learn about all of the free UC IPM resources available to help you manage pests in the home, garden, or landscape!
Below are answers to the 2023 Easter Egg Hunt! How did you do?
Some mosquitoes lay single eggs on water surfaces, while others, like Culex species, lay batches of 100 or more eggs, called rafts, pictured above. Other species lay single eggs just above the water line in moist soil, tree holes, or containers where later flooding is likely. Eggs deposited on water surfaces usually hatch within a couple of days, but eggs laid on the sides of saucers under plants, jars, cans, or soil surfaces won't hatch until flooding occurs, which can be months or even years later. Read the Pest Notes: Mosquitoes to learn more.
Squash bug eggs are laid in groups or clusters of 15 to 40 on the underside of leaves in the spring. The bugs hatch and feed on squash plants as juveniles and adults. See the Pest Notes: Squash Bugs for more information about these garden pests.
Spined assassin bug eggs are laid in groups. These beneficial insects or “natural enemies” are predators that feed on other small to medium sized insects. Visit the UC IPM website to learn more.
Cockroach eggs are laid in a case, called an ootheca. American cockroaches carry the egg case from their abdomen for only a short time before depositing it in a suitable location where it incubates for weeks or months. View Pest Notes: Cockroaches to learn more.
Green lacewing eggs are laid on slender stalks. Female lacewings lay about 100 to 300 eggs during their several-week lifespan. Larvae and adults are predators of soft-bodied insects. Read more about these natural enemies and learn to recognize them on the UC IPM website.
