- Author: Lauren Fordyce
Most people don't think about rats or mice until they become pests in or around the home. But with experts predicting that these pests will be particularly bad this upcoming winter, you might want to spend some more time rodent-proofing your home and other buildings.
A new report from the National Pest Management Association (NPMA) predicts an increase in rodent infestations from the cool, wet weather we've had in California. When temperatures drop outdoors, rodents often seek shelter in buildings to keep warm. They can enter through small cracks in foundations, screens, or trim. Once inside, they can damage the structure, destroy food, and transmit diseases to humans and other animals.
Some general tips for keeping rats and mice out include:
- Check around foundations, roofs, water pipes, vents, and utility cables for openings. Seal exterior cracks and holes larger than ¼ inch with wire mesh, steel wool, sheet metal or concrete. Rodents can chew through caulk, expanding foam, plastic, wood, and other soft materials.
- Make sure all exterior doors and windows fit tightly.
- Keep food storage and garbage containers sealed. Store pet food in rodent-proof containers and avoid leaving excess pet food out.
- Clean up crumbs or spilled food immediately.
- Remove or thin vegetation around buildings. Roof rats will use climbing vegetation to scale buildings and seek shelter.
If you have rodents indoors, the best way to control them is with snap traps. Dispose of dead rodents by placing them in plastic bags and putting them in the garbage. Do not touch rodents with your bare hands.
Learn more about managing rodents in the UC IPM publications Pest Notes: House Mouse and Pest Notes: Rats. If your rodent infestation is too much for you to handle on your own, consider Hiring a Pest Control Company.
- Author: Saoimanu Sope
Living with pests, or “unwanted guests” as some put it, can take a physical, mental and economic toll. For people living in multi-family unit housing, like an apartment complex where everyone lives under one roof, a single infestation of insects or rodents can expose all residents.
Using integrated pest management, or IPM, residents and property managers can detect infestations early and control severe ones and protect people. IPM programs can also save money. IPM saved a 75-unit complex in Contra Costa County $11,121 annually. Similarly, in Santa Clara County, a 59-unit complex saved $1,321 on pest control annually after implementing a proactive IPM program.
This summer, regional directors, property managers, residential service coordinators, maintenance managers and groundskeepers of Mercy Housing – a nonprofit organization that provides affordable, low-income housing – gathered in Long Beach to learn about in-home IPM. The session was led by Siavash Taravati, University of California Cooperative Extension area IPM advisor for Los Angeles, Orange, Riverside and San Bernardino Counties, and
Josh Shoemaker, an entomologist and private consultant.
Taravati and Shoemaker collaborated with StopPests in Housing, a national program out of Cornell University's Northeastern IPM Center, which seeks to improve pest control in affordable housing and teach management practices for cockroaches, bed bugs and rodents within and around the home.
During their presentation, Taravati introduced participants to the IPM principles and emphasized the importance of monitoring pests.
“IPM is all about making informed decisions which requires knowing the latest status of an infestation,” explained Taravati. “That's where monitoring comes into play. It can help us to identify the exact species we are dealing with as well as telling us if an infestation is growing or shrinking.”
“Monitoring is foundational,” agreed Shoemaker. “If a program does not include monitoring, it's not an IPM program.”
According to Shoemaker, the benefit of partnering with UC IPM is their sharp focus on general IPM, which includes monitoring. “It's real IPM, that prioritizes the well-being of the public,” said Shoemaker, who's eager to continue working with Cooperative Extension and Taravati to ensure that children are growing up in safe environments.
Pest control treatments commonly take place following a serious infestation or several complaints, but IPM promotes constant monitoring to prevent heavy infestations from ever happening. It's a proactive approach rather than a reactive or emergency-response. For many attendees, the training revealed a need to engage with pest management operators more closely.
Training prompts changes that improve safety for residents
Pest management operators commonly use pesticide sprays to control pests. Besides inconveniencing residents, forcing them to do extensive preparations and evacuate their unit until it's safe to return, sprays increase exposure risk to pesticides since the aerosols can linger and land on surfaces.
Instead, Taravati and Shoemaker recommend using gel baits, which are much safer to apply and can target a specific area of a home, including crevices, instead of along all the walls.
“Now that I'm more informed, I'll be speaking to my contractor to discuss how we can switch their approach from a bug spray to a gel,” said Leonardo Pinuelas, a maintenance manager for Mercy Housing.
Pinuelas is not the only one wanting to modify their program, however. According to feedback from staff members at the Housing Authority of the City of Los Angeles who experienced the same training earlier this year, they prompted their team to amend their pest extermination to include dusting, or applying insecticidal dusts, against roaches, and to review and update their existing IPM plan and practices where appropriate.
Cindy Wise, area director of operations for Mercy Housing, said that in her 35 years, this was one of the few trainings that engaged her staff so actively. “I couldn't help but text my regional vice president to say that our managers were actively participating and asking questions. That doesn't happen often, not even in our own meetings,” said Wise.
Many of the attendees, with their new understanding of how cockroaches move through a structure, shared that they are eager to return to work to meet with residents and support them.
“If you've got roaches in one unit, you've got them in the entire building,” Wise said.
Shoemaker recalls the words of Judy Black, senior technical entomologist for Orkin, and Dini Miller, entomologist at Virginia Tech, who urge the importance of inspections and documentation as IPM best practices.
Although reporting pests in the home can make one feel embarrassed, Wise said she is more interested in making residents feel empowered to not only report signs of infestation to the staff, but to their neighbors.
Training residents is certainly beneficial, but as experts such as Black and Miller have pointed out, housing managers must do their part, instead of scapegoating tenants for their cleaning habits.
StopPests provides free IPM training and technical assistance to Housing and Urban Development assisted properties. If you are interested in the training provided by Taravati and Shoemaker, in collaboration with StopPests, visit StopPests.org for more information.
- Author: Ben Faber
U.S. EPA proposed changes to rodenticide labels for agricultural use:
opportunity for public comment
Roger A. Baldwin, Professor of Cooperative Extension, UC Davis
Niamh Quinn, Cooperative Extension Advisor, UC South Coast Research and Extension Center
Rodents cause substantial damage and health risks in agricultural productions systems through direct consumption of fruit, nuts, and vegetative material; damage to the plant (e.g., girdling of stems and trunks); by providing a food safety hazard from contamination; damage to irrigation infrastructure; damage to farm equipment; burrow systems posing a hazard to farm laborers; posing a health risk through potential disease transmission; and increased soil erosion by water channeling down burrow systems, among other potential damage outcomes. They also cause substantial damage and food contamination risks in livestock holding facilities, food processing facilities, barns, and other agricultural-related structures. As such, effective management is needed to minimize these risks. The use of rodenticides is often considered the most efficacious and cost-effective tool for managing rodent pests, and as such, it is often included in Integrated Pest Management (IPM) programs designed to mitigate rodent damage and health risks. Given the significance of rodenticides in managing rodent pests, it is important to know that the U.S. EPA has recently released a list of Proposed Interim Decisions (PIDs) for public comment that, if approved, will substantially alter if and how rodenticides may be used to manage rodent pests in the near future. As such, we felt it was important to inform California's agricultural producers as to the extent of these proposed changes, and if you are so inclined, we have provided a link for you to provide public comment on the PIDs, as well as links to contact your Senate and Congressional representatives to ensure your opinion is heard.
All rodenticides are currently under review. These include first-generation anticoagulants (FGARs; chlorophacinone, diphacinone, and warfarin), second-generation anticoagulants (SGARs; brodifacoum, bromadiolone, difethialone, and difenacoum), zinc phosphide, strychnine, bromethalin, and cholecalciferol. Of these, only FGARs, zinc phosphide, and strychnine have labels for use against field rodents (e.g., ground squirrels, pocket gophers, voles, rats, and mice found in agricultural fields), but not all of these active ingredients can be used for all rodent species. As always, it is imperative to fully read a rodenticide's label before determining if it is appropriate for use against a particular species and in a specific situation. That said, the following are some significant changes that have been proposed that you should be aware of. Other potential changes have been proposed as well, so please check out the PIDs for additional details (linked at the end of this document).
- All rodenticides for field applications will become restricted-use products. This means that applicators will need to be certified to use restricted-use products in these settings. They will also have increased reporting requirements for their use.
- Aboveground applications would be eliminated in rangeland, pastureland, and fallow land. This is a substantial deviation, as many/most applications in these areas have traditionally been through broadcast applications or spot treatments. This change would leave only bait stations for ground squirrels and voles.
- Within-burrow applications of FGARs will generally not be allowed in croplands during the growing season. This would eliminate FGAR application for pocket gophers for much of the year, and would eliminate it for all uses in some crops (e.g., citrus and alfalfa in certain areas of the state).
- Carcass searches will be required every day or every two days (starting 3-4 days after the initial application), depending on the product used and where applied, for at least two weeks after the last application of the rodenticide. When carcasses are found, they must be disposed of properly. Any non-target mortalities must be reported to the U.S. EPA. Collectively, this will require a major increase in labor, potentially making rodenticide applications impractical in many settings.
- Extensive endangered species designations are anticipated that will limit or eliminate the potential to apply rodenticides. This could have large-scale impacts, although the full extent is not known at this time.
- New labels will require the use of a PF10 respirator and chemical resistant gloves during application. This is a substantial change for some rodenticide labels, requiring fit testing for all applicators, with the requirement of respirators ultimately making rodenticide application more physically challenging.
Additional details on these proposed changes can be found at the following websites:
- Anticoagulant PID: https://www.regulations.gov/document/EPA-HQ-OPP-2015-0778-0094
- Zinc phosphide PID: https://www.regulations.gov/document/EPA-HQ-OPP-2016-0140-0031
- Strychnine PID: https://www.regulations.gov/document/EPA-HQ-OPP-2015-0754-0025
- Bromethalin and cholecalciferol PID: https://www.regulations.gov/document/EPA-HQ-OPP-2016-0077-0024
As mentioned previously, these proposed changes are likely to have a substantial impact on the use of rodenticides in agricultural settings. However, these changes are currently open for public comment. If you would like to comment on these proposed changes, the required links and useful guidance can be found at the following website: https://responsiblerodenticides.org/.
You may also comment on these proposed changes to your Senate and Congressional representatives. If you are unsure who they are or how to contact them, check out: https://www.congress.gov/contact-us.
The deadline for making comments to the U.S. EPA is unfortunately short, with a final deadline of February 13, 2023. Therefore, you will need to provide your comments in short order.
- Author: Niamh M Quinn
Where is rodenticide exposure in wildlife coming from? Is it from use by residents or farmers? Applications by marijuana growers? Or from applications by qualified and trained structural pest control professionals? These questions are being asked by state legislators and regulators, special interest groups, and state pest associations across the country.
However, even though we don't fully know where all the exposure is coming from, action is already being taken to restrict the use of rodenticides in urban areas. In 2020, California legislators placed a moratorium on almost all uses of second-generation anticoagulant rodenticide. And local jurisdictions have also added restrictions to rodenticide use. For example, in southern California, the California Coastal Commission granted special approval to the city of Malibu to ban all uses of rodenticides.
What's being done?
Researchers at the University of California Division of Agriculture and Natural Resources (UC ANR) South Coast Research and Extension Center in Irvine have been examining some of these questions over the past seven years. UC ANR's Human-Wildlife Interactions Advisor Dr. Niamh Quinn and colleagues have looked at urban coyotes' exposure to anticoagulant rodenticides (ARs), which active ingredients they were exposed to, and the amounts of AR exposure.
Almost all coyotes examined had been exposed to at least one anticoagulant rodenticide and usually, multiple active ingredients (Table 1). Some were exposed to low amounts of ARs and some were exposed to very high levels. However, less than 1% of the coyotes examined had died from AR exposure. Recent studies on the sublethal effects of exposure have not shown any clear links between AR exposure and sublethal impacts (such as reduced body condition or parasite load). There is also no link between AR exposure and mange in coyotes in urban southern California.
Do coyotes eat rats?
The diet of the urban coyote in southern California was questioned, specifically “Do they eat roof rats?” and “If they don't eat roof rats, how else could they be getting exposed to anticoagulant rodenticides?” It turns out that coyotes do eat rats (Figure 1). They eat a variety of other things too, but rats are among their preferred mammalian prey items, along with rabbits and domestic cats (Table 2).
In one of the first studies of its kind, we examined which animals were actually visiting rodenticide bait stations. We were surprised to find that in southern California, it is mostly roof rats, rather than nontarget animals. This was confirmed in another study sponsored by BASF. In southern California, less than 1% of mammals entering bait stations in urban area were nontarget wildlife. This is good news!
However, if pest management professionals are using anticoagulant rodenticide and are exposing just roof rats, and coyotes are eating said rats, does this mean that legal applications are responsible for the urban coyote AR exposure?
Another interesting finding from these studies concerned how rats use bait stations. With non-toxic baits used during this study, we photographed rats entering only 59–70% of the bait stations, suggesting that roof rats may be reluctant to enter bait stations, even when no rodenticide was present. Even in yards where rats eventually entered stations, it took 7 to 8 days for them to first encounter the bait directly.
What does this mean?
Because the first mortalities from anticoagulant rodenticide might not occur for several more days, pest management professionals should be prepared to communicate these possible delays to their customers. This will prevent customers from becoming impatient and taking more drastic (and potentially illegal) measures when results are not immediate.
Tracing applications of anticoagulant rodenticides
The ability to trace the applications of anticoagulant rodenticides has been lacking, but we may have developed a method to trace AR movement. We have created a bait that can be traced up multiple levels of the food chain. Therefore, we will be able to finally trace the rodenticide bait from its point of application to see if a legal application of anticoagulant rodenticide ends up in multiple levels of the urban and suburban food chain.
Two separate studies were conducted to see where animals exposed to anticoagulant rodenticides die and what scavenges them. One was conducted by Dr. Roger Baldwin in an agricultural setting and one by Dr. Paul Stapp from Cal State Fullerton in the suburban environment. Dr. Baldwin discovered that ground squirrels exposed to first generation anticoagulant rodenticides were mostly dying below ground (Figure 2). Dr. Stapp discovered that rats left in backyards are scavenged on by all sorts of animals including crows, skunks, opossums, and domestic cats. After 7 days, almost all (65%) of the carcasses had been either partially removed or removed completely.
Do coyotes and other large predators also scavenge rats? In research conducted in Europe, 92% of dead rats were inaccessible to large predators and scavengers. It is thought that rats killed by brodifacoum in and around farm buildings don't seem to present a major secondary exposure risk to large vertebrates.
What is next for rodenticide research?
We are developing methods to monitor rodenticide exposure in wildlife in a more meaningful way. The Quinn Lab and other institutions are working on methods to sample for rodenticides in live mammals and birds of prey with the aim of being able to detect any population -level impacts of rodenticide exposure. These methods will provide a mechanism by which rodenticide exposure can be monitored in live populations.
There is a huge need for data-driven mitigation measures for rodenticide exposure in California. We have been testing the efficacy of different management practices. We are testing trapping only, second-generation anticoagulant only, and a mix of both trapping and anticoagulant rodenticide. Using a combination of tracking rodents by collaring them and measuring how long it takes them to die, and by using tracking tunnels, we are measuring how quickly and how effectively these management options manage roof rat populations in southern California.
A mutation associated with second-generation anticoagulant rodenticide resistance, the Y25F mutation, has been found in roof rats in California. We don't know what this discovery means for rats in California. We need to explore more and find out to what extent they are resistant. Resistance management is essential for prolonging the life of all pesticide active ingredients.
Rodent management is complex, time consuming and we are tackling the unknown. We know more about polar bears than we do about commensal rodents. We need to know more to address inadequacies in rodent management. To reduce the amount of secondary AR exposure in the environment, it is necessary to ensure that rodent populations do not rebound and that they are not continually being exposed to active ingredients that can bioaccumulate in the food chain. If predators continue to eat commensal rodents, it is important to figure out ways to reduce the number of them that are exposed to rodenticides.
What does the future of rodent management look like?
It is important to continue work with municipal managers, schools, and customers to ensure that they do their parts. Exclusion and sanitation must be important components of a rodent management plan, especially as there continue to be restrictions on rodent management tools. In some countries, the sale and use of glue boards to catch rodents are prohibited. Certain snap traps have failed rigorous testing in some countries and are considered to cause unacceptable pain and suffering so are prohibited for use. It is important that pest management professionals use tools according to labels and trapping specifications. PMPs must rely on safe and effective methods.
Managing rodent populations such as roof rats is increasingly difficult since there are expanding restrictions on management tools and a dearth of applied research on commensal rodents. To solve these issues, we must find more sustainable and effective management practices.
Our funders and collaborators for these research projects were Cal State Fullerton, the Pest Management Foundation, the California Structural Pest Control Board, the National Wildlife Research Center, California Department of Pesticide Regulation, California Department of Food and Agriculture, and the Anticoagulant Taskforce.
[Originally featured in the Summer 2022 edition of the Green Bulletin Newsletter for structural and landscape pest professionals.]
/h2>/h2>/h2>/h2>/h2>/h2>- Author: Ben Faber
Burrowing Rodents: Developing a
Management Plan
for Organic Agriculture in CA
RELATED ITEMS
- California ground squirrels Otospermophilus spp.
- Pocket Gophers Thomomys spp.
- Meadow voles Microtus spp.
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