[Originally published in the Summer 2022 issue of the UC IPM Green Bulletin]

The three-lined cockroach, Luridiblatta trivittata, (Figure 1) is the smallest cockroach species in California, with adults averaging only 5–7 mm in length. This newly introduced cockroach is native to North Africa and the Eastern Mediterranean. It was first detected in California around 2004 in Marin County, but it was not positively identified until 2009. Since then the three-lined cockroachhas slowly expanded its range to include the entire San Francisco Bay Area, south to San Luis Obispo, east to the foothills of El Dorado County, and north to Mendocino County.

Fig. 1. Three-lined cockroaches. [Credit: Casey Hubble, UCCE]

Life cycle and biology

The three-lined cockroach lives in some of the most densely populated parts of northern California, but it's not a domestic pest species since it is rarely found indoors. Instead, these cockroaches prefer to live outdoors in natural or ornamental landscapes and can be found in matted thatch, compost bins, and leaf litter. Occasionally in late summer and early fall, adults will wander indoors through poorly sealed exterior doors and windows.

When inside, they are often misidentified as German cockroach nymphs (Blattella germanica), sometimes leading to unnecessary indoor insecticide applications. However, the number of stripes on the cockroach's body can help distinguish the species. The three-lined cockroach has three distinct stripes that run down the length of the adult's body, while German cockroach adults and nymphs have only two stripes (Figure 2).

It is unclear what the three-lined cockroach likes to eat in the landscape. Within the San Francisco Bay Area, this species has been observed feeding on the juices from overripe fruit in trees, and various food scraps from compost bins. Though these food items may be delicious treats for the cockroaches, they would appear to be atypical meals, since large populations of this insect have been found far from fruit or human food resources. Though scant, existing scientific literature classifies them as detritivores (organisms that feed on decaying organic material, especially plant matter), but it is unclear exactly what kinds of detritus might be preferred. Unfortunately, this question remains a mystery, since insect field diets can be notoriously difficult to determine.

Virtually no research has been conducted on this species, even in its native range. To better understand the biology and ecology of L. trivittata in California, the SF Bay Area Urban IPM Team launched a field study and several lab studies in 2021, revealing some interesting observations:

• Three-lined cockroaches have only one generation per year (Figure 3).
• Juveniles hatch in mid-April and develop through spring and early summer, eventually maturing into adults during July and August.
• Once mature, females lay egg cases (called oothecae) that will overwinter until next spring. Oothecae start out mint green in color, and as they develop, turn from olive green to dark brown before they are deposited into the landscape (Figure 4).

Mediterranean climates with long dry summers and short wet winters, found in California as well as their native habitat, seem to be ideal for this species. Juveniles do not seem able to hatch from their oothecae without some spring precipitation. On the other hand, too much water throughout the overwintering cycle may cause the eggs to mold, killing the nymphs before they can hatch. Females lay on average two or three oothecae per year. Each ootheca is very small (2 mm in length) and contains about 10 tiny cockroaches on average. This number is smaller than that observed for other outdoor cockroach species in California, where most average between 11-21 nymphs per ootheca.

The common name “three-lined cockroach” was suggested by the SF Bay Area Urban IPM team and officially adopted by the Entomological Society of America. This name is not only an accurate description of the insect's appearance but is also reflected in the scientific name Luridiblatta trivittata.

What can you do?

Proper identification is crucial to providing effective pest control services. While the three-lined cockroach prefers to live outside (only occasionally wandering indoors), the German cockroach lives exclusively indoors and is considered a major public health pest. Signs of the three-lined cockroach indoors may signal the need for better structural exclusion while German cockroach infestations will need immediate remediation. If you are unsure of the pest species, contact your county's UC Cooperative Extension office, Department of Agriculture, or Vector Control District for confirmation.

Though the three-lined cockroach may be considered a nuisance pest when found in large numbers, it may not ever call for control measures. There are many unknowns remaining about this species, such as how far it may expand throughout California and neighboring states. To help us track the spread of the three-lined cockroach, you can submit photos and report sightings to iNaturalist (https://www.inaturalist.org/) or BugGuide (https://bugguide.net/node/view/15740); these civic science data can be pooled to create distribution maps (Figure 5).

This research was funded by the California Department of Pesticide Regulation.

References:

California Plant Pest & Disease Report Vol. 25. 2009. CDFA

Sutherland AM, Choe D-H, Rust MK. 2019. UC IPM Pest Notes: Cockroaches. UC ANR Publication 7467. Oakland, CA.

Djernæs, Marie, et al. "Phylogeny and life history evolution of Blaberoidea (Blattodea)." Arthropod Systematics & Phylogeny 78.1 (2020): 29-67.

It's that time of year again: termite swarm season! Western subterranean termites, Reticulitermes hesperus (species complex), produce reproductive swarms during calm sunny periods immediately following the first autumn rains. This is especially pronounced in the San Francisco Bay Area and parts of the Sacramento Valley, where mature termite colonies across a broad region may swarm simultaneously en masse, filling the air with termites fluttering their gossamer wings and filling social media discussions with wonder, horror, confusion, and dread.

Western subterranean termites may also swarm in the spring, especially in southern California, foothills of the Sierra Nevada, and the northern Sacramento Valley. No matter the swarm season, the goal for the termites is to form “nuptial pairs” of virgin “queens” and “kings” that will mate and venture out into the landscape to start their own colonies, which may eventually consist of hundreds of thousands of individuals that forage over thousands of square feet! Seeing fluttering termites in the air means that nearby colonies are swarming, but it does not necessarily mean your home or other wooden structure is infested. On the other hand, seeing winged termites issuing forth from the ground or a piece of wood means, unequivocally, that there is a mature colony underneath, potentially infesting or threatening nearby wooden structures.

What should you do? If observing a swarm on your property, especially if near your home or other structures, you can hire a professional termite company for a detailed inspection. Make sure to photograph or otherwise note the swarm location so that the inspector can start there. Even if you don't see swarms on your property, regular (every three to five years) inspections will help detect infestations before they cause significant damage and prevent future infestations. There are several proven management strategies for termites; review UC IPM's Pest Notes: Subterranean Termites.

For now, perhaps we can all appreciate the wonder of this natural spectacle. Winged termites are great sources of food for birds, lizards, other insects, and spiders. Termites also provide important ecosystem services, such as decomposition of wood and fallen leaves, contribution to soil structure formation, enhancement of water infiltration in soil, and facilitation of nutrient availability to plants. Furthermore, western subterranean termites are native to California and have been here long before we built wooden structures on top of their colonies. (Termite) love is in the air!

Bed bugs can hitch rides on secondhand furniture, luggage, backpacks and other personal items to invade homes and attack people. While we rest and sleep on sofas and beds, the insects come out to feed. They want to suck our blood. A new web-based, interactive training course shows how to prevent and detect bed bug infestations.

“The training helps tenants recognize, restrict and report bed bugs and helps landlords comply with California state regulations on bed bugs,” said Andrew Sutherland, University of California Cooperative Extension integrated pest management advisor for the Bay Area.  

Landlords are required by Assembly Bill 551, which became law in 2016, to provide bed bug information to renters in California. Renters and other residents can learn how to spot signs of bed bugs from an online course designed by UC Agriculture and Natural Resources integrated pest management experts, web designers, pest management professionals, housing management professionals and public health officers. 

The online bed-bug education is available in full-length and shorter versions in both English and Spanish. The animated, fun and self-paced course is available for free at stopbedbugs.org.

Although bed bugs have never been shown to transmit disease to humans, their bites can cause itchy, red welts on the skin.

People shouldn't be embarrassed about having bed bugs, says Sutherland. Cluttered spaces give bed bugs places to hide and breed, but the tiny insects don't require a dirty environment. Even the nicest hotels sometimes play host to bed bugs.

“This training will help destigmatize having bed bugs and, by emphasizing prompt reporting and cooperation, will help landlords and residents fight bed bugs as a team,” said Heidi Palutke, senior vice president of compliance and education for the California Apartment Association.

Bed bugs can go without feeding for many days to several months, depending on life stage, temperature and humidity, according to the UC Integrated Pest Management Program. Adult bed bugs may live one year or more and produce as many as four generations.

The bed bug course was produced with funding from the California Department of Pesticide Regulation. The digital artistry was created by Sergey Litvinenko and his colleagues at Geosphere LLC.

 

[Originally published on the Healthy Communities Blog]

Most pest management professionals have served clients who swore they were being bitten by unseen pests. Perhaps the usual suspects (bed bugs, fleas, and mosquitoes) were ruled out by thorough inspection and monitoring devices. But what about mites? There are several species of mites known to bite humans within homes and other structures, many times causing significant physical symptoms and psychological distress. Clients can easily fall prey to misinformation online when learning about these tiny pests, however, so be prepared to educate them and help them solve their problem.

In all cases, biting mites found indoors are blood-sucking nest parasites of other animals living nearby, especially rodents or birds. The most common species in California, the tropical rat mite (Ornithonyssus bacoti) (Figure 1), is often associated with the nests and runways of roof rats and other commensal rodents. Also common are northern fowl mites (Ornithonyssus sylviarum), known to inhabit nests of commensal birds, such as pigeons, starlings, sparrows, and swallows. Less common but perhaps increasing in prevalence is the chicken mite or red mite (Dermanyssus gallinae).

All three of these common species will take blood meals from humans, especially if their primary hosts have been controlled, removed, or have migrated away. For instance, successful rat control programs (Figure 2) may result in hundreds of starving rat mites wandering nearby areas in search of blood. If rats were nesting in wall voids, attics, subareas, or living spaces, then there is a good chance the resident rat mites will be attracted to the humans in the structure when the rats are no longer around.

A similar phenomenon occurs when migratory birds leave nests in autumn if nests are situated in window alcoves, eaves, or other areas abutting a living space. With the rise in popularity of backyard chickens (Figure 3), primary hosts for both northern fowl mites and chicken mites, problems can occur when coops are adjacent to walls of the home or near windows or exterior doors. Mite populations associated with chickens reportedly peak and are most likely to affect humans in spring and summer, while rat mite issues tend to be most common in late summer and autumn. Problems can occur any time of year, of course, when the primary host has been removed.

Detecting Mites

Mites may become trapped on sticky traps and glue boards placed at floor-to-wall junctions and in corners; look at the edges of the glue deposit on these traps with a 10X hand lens. Another detection trick is to use double-sided tape. With the client's permission and guidance, apply double-sided tape to walls and furniture legs near areas where bites have occurred; wandering mites may become stuck on the edge of the tape. Sticky traps and tape may not preserve mites well enough for positive identification, but they can confirm that mites are present and may be responsible for the bites.

Such monitoring tools can also give clues as to where the nest of the primary host is or was. In multi-unit housing situations, the source of these wandering mites may be in adjacent units, the hallway, stairwells, or utility areas. In single-family homes, the source may even be outside, such as a bird or rat nest in the landscape. Tropical rat mites are known to travel along pipes, utility wires, tree branches, fencing, and exteriors of structures to find new hosts.

Identifying Mites

The best way to confirm a biting mite issue is to capture a specimen. Though very small (about 1/16 inch (1.5 mm) or less in diameter), all three common species can be observed without magnification. Mites may be yellowish or whitish before feeding but will be dark red when engorged with blood. Ask the client about areas of the home where bites are most common. When active, mites may be seen crawling on walls, floors, or furniture. For positive identification, mites should be captured alive and preserved in rubbing (isopropyl) alcohol or ethanol (at least 70%). This can be accomplished with the help of a fine wet paintbrush and a ready vial of alcohol.

Identification to species requires clearing and slide mounting of the specimen and close examination by an acarologist (mite specialist). Some county vector control programs can identify mite specimens and some entomologists can prepare and photograph specimens, but there are few acarologists in California who may be able to provide identification services. Be prepared for such positive identification to take a week or longer.

Managing Mites

Once mites have been confirmed, management should focus on removal of the primary hosts and their nests. Humans are incidental hosts and are not known to support reproducing populations of Ornithonyssus and Dermanyssus. That means that, in theory, once the rat or bird hosts have been eliminated from the structure, the mites will slowly die. Depending on temperature, season, and mite life stage, however, this could take weeks. Some experts report that tropical rat mites can survive without primary hosts for six weeks or longer, feeding incidentally on humans and their pets that entire time, often causing red itchy welts.

If the source of the mites is known, exclusion services can be offered to seal the pest's access points. Regular vacuuming and surface cleaning will remove or kill wandering mites and so should be recommended to your client or provided as part of your service. Also, pulling beds away from the walls can be very effective. As soft-bodied arthropods, mites are vulnerable to contact insecticides such as soaps and oils, but these products may not be labeled for indoor use and may damage wall coverings, flooring, and other furnishings. Some professionals have had success with essential oil products and even claim they provide short term repellency, but research has not been conducted to confirm these observations. Residual insecticides, especially pyrethroids, may be effective against mites, and some are labeled for use indoors. Such products should be applied between suspected mite sources and areas where bites occur, in narrow bands on surfaces unlikely to be touched by residents. Insecticides will not solve a biting mite problem if the primary hosts are still present. In all cases, refer to product labels to ensure legal application site, method, and rate, and to prevent damage to furnishings.

Biting mites may be more common than we realize, escaping detection due to their small size and their cryptic habits. Much research still needs to be done to better understand the biology and ecology of these pests as well as to develop effective monitoring and management tools. Sometimes, mites cannot be detected, and rodents and birds are seemingly not present, but your client's dermal symptoms (“bites”) persist. In such cases, it may be prudent to consider other causes of dermatitis, such as environmental irritants, reactions to medications or drugs, stress, some medical conditions, or even delusional infestation (aka delusory parasitosis), a psychiatric condition. A newly revised UC IPM publication, Pest Notes: Itching & Infestation: What's Attacking Me?, may help identify the problem. To learn more about management of commensal rodents and birds, review these UC IPM titles: Rats, House Mouse, and Cliff Swallows.

[Article originally published in the Fall 2020 issue of the Green Bulletin.]