- Author: Niamh M Quinn
- Author: Roger A Baldwin
- Author: Carolyn Whitesell
Pocket gophers can cause significant damage to valuable turf, girdle trees, and chew irrigation lines. Their mounds can create tripping hazards and lead to erosion concerns when found on slopes. Luckily there are multiple successful management options to choose from when it comes to managing pocket gophers.
Do I have a pocket gopher?
Pocket gophers are small burrowing rodents that are often identified from the damage they cause rather than a sighting of the animal itself. Pocket gophers spend most of their time below the surface and while it is possible to see them above the ground, or peeping out of a burrow (Figure 1), the easiest way to determine the presence of pocket gophers is by the crescent-shaped mounds they leave behind on the surface from excavating their burrows. Pocket gopher mounds can be differentiated from mole mounds by their shape—mole mounds will be round whereas pocket gopher mounds have the distinctive crescent shape. Pocket gophers do not hibernate and are active year-round, so it is important to be vigilant when managing pocket gophers.
Management options
There are many management options for pocket gopher control and in California, significant research has been conducted to better utilize and examine the effectiveness of many of these tools. While there continues to be restrictions on some of the toxic options for pocket gopher management, there are still multiple non-chemical options to choose from that fit well into an IPM plan. Pocket gopher trapping has proven to be one of these very effective methods.
Trapping
Trapping is an excellent option for managing pocket gophers, even if you think you have a large population. In general, there is only one pocket gopher per tunnel system, so once you have captured one, you can move to the next system. Be aware that during the breeding season, there could be both a male and female in the burrow system, and after the female gives birth and the pups are dispersing, you can find the pups in the burrow system with reproducing females. In these scenarios, you might capture more than one pocket gopher per trap set.
Trapping takes longer when compared to toxic bait application or burrow fumigation with aluminum phosphide but it can be highly effective when done correctly.
Make sure you have the right tools when it comes to trapping pocket gophers. It is important to have sufficient traps for the population you are dealing with. Focus trapping efforts on fresh mounds, as older mounds are less likely to be active. If you are unsure what mounds are active, you can knock over all mounds and trap at the new mounds that appear. Pocket gophers may not mound every day, so trap over more than one day to be successful. It is worth noting that it can be difficult to determine individual burrow systems from each other. Some practice is required to better define which mounds are likely from the same individual. If a trap set is not successful after 1 or 2 days, move it to a new tunnel location.
Trap selection (Figure 2) and placement may be important when choosing trapping as your pocket gopher control method. In studies, the Gophinator trap caught larger pocket gophers at a higher rate than the Macacbee trap. In addition, these traps often require larger excavations in the soil. For areas like high value turf, these traps may not the best option. An alternative trap is one resembling the GopherHawk, which may cause less damage because they don't require as large of an excavation in the soil.
When you set a pincher-style trap like the Macabee or the Gophinator, or a box-type trap like the Black Box or Black Hole, it is important to locate the main run of the burrow system. To do this, take a long metal rod like a screwdriver and probe around the mound. You will need to stick your probe into the ground at depths of about 4 to 12 inches. When you find the tunnel, you will experience a sudden drop in resistance. This skill is difficult to acquire but will improve with practice. Once you have located the main run, you need to excavate an opening in the tunnel to allow for setting of the trap. You can use a hori-hori knife or a trowel to make this hole, which may need to be more or less extensive depending on which style trap you choose.
If you are using a pincher-style trap that is set inside the tunnel, make sure that the tunnel you are setting the trap in is straight. You can check this by putting your excavator tool into the tunnel and making sure that at least 6 inches of it fits into the tunnel. This way you know the tunnel doesn't turn; tunnels with turns often allow the pocket gopher to bypass the jaws when activating the trap, thereby resulting in triggered traps that miss the gopher.
Several attractants have been tested but they did not influence visitation or capture rates of pocket gophers to traps. Attractants also did not influence the gender of pocket gophers captured. There is no impact of human scent on the success of trapping pocket gophers.
Is blocking light by covering trap sets necessary when trapping for pocket gophers? Covering and uncovering pocket gopher trap sets is time consuming and does not result in a greater number of captures. However, if you are trapping in areas with high foot traffic, there may be some benefits to covering your trap sets. You can cover the traps with sod, landscape cloth, or something like cardboard or plywood to prevent people or pets from interfering with your trap sets. In general, it is recommended that you cover sets when using box traps, since pocket gophers will likely plug tunnels before hitting the trigger wire of these traps if you leave them uncovered.
It can be helpful to tie a flag to the traps so you can easily remember where they were set. This can also help you recover the trap if the gopher drags it away.
When you recover a dead pocket gopher, remove it from the trap, put the gopher back in the tunnel, and cover it up. You can also double bag the animal and place it in the trash. Always wear gloves when handling pocket gopher or any other wildlife carcasses.
Toxic baits
There are several options for pocket gopher management using toxic baits. It is important to ensure that bait is placed correctly in the tunnel either by using a probe with a bait applicator or by hand using a funnel and spoon. Always read and follow the label. Many toxic baits that are used to manage pocket gophers require a restricted materials permit. However, there may be exemptions for products applied for structural pest control, industrial use, and institutional use.
Strychnine is the most effective type of bait used for pocket gopher management. This toxicant is an acute rodenticide where a lethal dose can be acquired after a single feed. Pocket gophers can develop behavioral resistance to strychnine. This enables pocket gophers to consume what is normally more than the lethal amount by periodically eating sublethal amounts. Pocket gophers also can be physiologically tolerant to strychnine since after they ingest a series of higher doses of strychnine, they can tolerate increasingly higher doses of it. It is important to rotate strychnine in with other management tools to avoid this type of resistance.
Zinc phosphide is also an acute rodenticide that is lethal after a single feeding. Bait shyness or taste aversion can be associated with this management option. Because of this, zinc phosphide may not perform as well as strychnine.
First generation anticoagulant rodenticides, including chlorophacinone and diphacinone, are multiple-feeding anticoagulants that are less toxic than strychnine and zinc phosphide. Since these baits require multiple feedings over 3-5 days, it is important to make sure that there is a continuous supply of bait during your treatment period.
Fumigation
Aluminum phosphide is highly effective, especially in moist soils. However, aluminum phosphide is a highly restricted material. It must be applied by a certified applicator, or the application must be supervised by a qualified applicator. You must have a restricted materials permit, a written recommendation to apply on production or non-production agricultural sites, and a Notice of Intent (NOI) from your local Agricultural Commissioner. You are also required to have a Fumigation Management Plan. You are not permitted to apply this product within 100 feet of a potentially occupied structure. The only place on school grounds where it is permitted to apply this product is on athletic fields.
Gas cartridges are not effective because pocket gophers seal off their burrow when they detect the smoke.
Carbon monoxide producing machines and carbon dioxide are registered for use in California against burrowing rodents. Carbon monoxide producing machines are registered devices, while carbon dioxide used for rodent control is considered a registered pesticide.
Carbon monoxide devices generate carbon monoxide which fills the burrow system and asphyxiates the pocket gopher. These devices include the BurrowRx, Cheetah Rodent Controller, CO Jack, and Pressurized Exhaust Rodent Controller (PERC) Machine. Research has shown that the PERC machine can be moderately effective at managing pocket gopher populations. Its efficacy increases in moist soil conditions. Some of these devices are more suited for urban applications and some for larger scale production agriculture. You are not permitted to use a carbon monoxide pest control device within 100 feet of a structure inhabited by people or domestic animals, whether occupied or not.
Carbon dioxide gas is a pesticide that is registered for use on several sites that include production agriculture, non-production agricultural sites, and residential areas. There are no distance restrictions for the application of this pesticide. It is important to follow the label. Solid carbon dioxide (dry ice) is not registered for use on pocket gophers.
Natural predators
Vertebrate predators—including owls, snakes, cats, dogs, and coyotes—eat pocket gophers. However, they will rarely control all pocket gophers in an area. Predators rarely remove every prey animal but instead move on to hunt in areas with more prey. In addition, pocket gophers have defenses against predators. For example, pocket gophers can evade snakes in their burrows by pushing up an earthen plug to block the snake's advance. Relying solely on natural predators might not control pocket gophers to the desired level. Research has shown that pocket gophers appear to be an important prey animal for barn owls nesting in perennial crops, and thus barn owls may be able to provide some pest control services in those areas.
Exclusion
Exclusion can be difficult and expensive for pocket gopher management, but it may be justified if you are trying to protect individual or high-value landscape plants. You can use hardware cloth (1/2-3/4-inch mesh) buried at least 2 foot deep with an additional 6 inches of hardware cloth bent at a 90° angle. You should also extend fences at least 1 foot above the ground because pocket gophers may move above ground to access the planting you are trying to protect. There are wire baskets available to protect individual plants or bulbs from pocket gophers. These baskets can also be fashioned from chicken wire. Remember that it is important not to restrict the growth of the plant inside the basket, so ensure the wire basket is large enough to accommodate the adult plant's root structure.
For more information about pocket gopher management, see the UC IPM Pest Notes: Pocket Gophers.
[Originally featured in the Spring 2024 edition of the Green Bulletin Newsletter for structural and landscape pest professionals.]
- Author: Elaine Lander
Integrated Pest Management for Rats
- Our Pest Notes: Rats has information to help you with identification, biology and IPM options.
- This blog post provides additional information on using snap traps to catch rats and mice.
- If you are managing a school or community garden, you can find rat management information in this blog post.
Our UC Guide Page on Tomatoes also provides cultural tips and information on managing tomato pests if you have invertebrate pests or tomato diseases.
Wishing you a bountiful harvest!
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- Author: Niamh Quinn
- Posted by: Elaine Lander
Trapping is the safest and most effective method for controlling rats and mice in and around homes, garages, and other structures. Rodents that live in close association with humans are called commensal rodents. Rats and mice are the most frequently encountered commensal rodents in California.
Selecting the correct trap
Before trapping, make sure you know what rodent pest you have. It is a very common mistake to select the wrong size trap when you have not yet determined whether you have mice or rats (and the correctly identified rat species).
You will not catch a rat with a mouse trap, and you will not catch a mouse with a rat trap. To determine the difference between signs left behind by rats and mice, see our Pest Notes Rats and Pest Notes House Mouse.
Select traps that you can easily set. Older designs of rat and mouse traps can be difficult to operate, so if you are having trouble setting these traps, consider buying a newer design.
Choose the right attractant
Food attractant is a very important part of successful snap trapping. Select an attractant the rodent would likely find locally available or that you know they are already feeding on. The amount to use is also critical. Select a pea-sized amount of the food attractant and carefully place it on the trigger or in the trap recess before you set the trap.
Food is not the only thing that can be used to lure rodents to your snap traps. When trapping mice, you can try to use small bits of cotton or dental floss, as the mice will try and collect these for nesting material.
Be cautious about using peanut butter in areas where you are unsure who will access the traps. Many people have peanut allergies.
When using snap traps for rats, it is good practice to prebait your traps. This involves putting the traps with a food attractant in areas where you find rat evidence while leaving them unset for a couple of days until this attractant has been removed multiple times. Because rats are neophobic (afraid of new things), you want to make sure the adults as well as the juveniles become comfortable with the traps. Failure to prebait may result in the capture of juveniles only. The breeding adults are the most important targets.
Use multiple traps in the right places
Good trap placement is essential. Set traps along a wall or fence line or another linear surface like the edge of a planter to maximize the success of trapping. Be sure to trap with the triggers either facing the linear surface or with the traps along the side of the wall with the triggers facing away from each other. Rats and mice are smart and resourceful animals, so set your traps in ways that take advantage of their biology. While many rats and mice will choose to run along linear surfaces, not all will. It is important to consider this if you are having problems with catching the last few remaining rodents.
Be mindful of nontarget wildlife
Rats and mice might not be the only wildlife roaming around the yard, so be aware of other animals (nontargets) that might get caught in traps. Nontarget wildlife, such as birds, and even larger wildlife, such as raccoons, can fall victim to rodent snap traps. Set traps only during the night, but leave them where they are during the day, making sure they are not set. This greatly reduces trapping animals that are mostly active during daylight hours. To exclude other larger wildlife, try placing traps under a secured (weighted or staked down) milk crate.
Securing the traps by staking or tying can help somewhat with nontarget issues too. One other benefit of securing your traps is that they will be easy to find when they are triggered. Predators can carry away dead carcasses and often will take traps too if rodents are attached, making it difficult to find traps and use them again.
Safely dispose dead rodents
Successful trapping involves disposing of the carcasses. Always wear gloves when removing rodents from traps or even when working with traps that have come into contact with rodents, dead or alive. Rodents are vectors of many diseases, so even when just moving dead rodents, it is important to protect yourself.
If you catch a rodent, remove the rodent from the trap, double bag it and put it in the trash. Many municipalities do not allow for the disposal of carcasses in municipal waste so be sure to consult your local ordinances before disposal.
If you don't want to remove the rodent from the trap you can throw both the rodent and the trap away. There are also traps available that catch mice inside the trap and kill them; you then dispose of the whole trap. These types of traps are not available for rats.
Don't give up!
You must persevere with your rodent problem when trapping. It can take a long time to effectively manage a rodent issue in your home or yard. Be persistent. An ongoing trapping program might be necessary in order to keep the rodent problem at the desired threshold. Rats and mice are prolific breeders, so as you trap these rodents out, more may eventually come and take advantage of the resources in your area.
Be sure to check out the Pest Notes Rats and Pest Notes House Mouse for tips and information on sanitation, exclusion, and other methods that may help you successfully manage your rodent issues.
[Original article published as Snap Traps for Rats and Mice in the Winter 2019 issue of the Retail Newsletter.]
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- Author: Andrew Sutherland
- Posted by: Elaine Lander
Two species of Blatta cockroaches can be common peridomestic pests in California, including the familiar oriental cockroach (B. orientalis) and a relative newcomer, the Turkestan cockroach (B. lateralis, Figure 1). Adults of both species are large (usually one inch or more in length) and conspicuous insects that harbor and breed outdoors within moist crevices around structures, such as subsurface utility ports, voids associated with concrete expansion joints, and soil cracks formed at junctions of landscape and hardscape elements (Figure 2).
From these harborage sites, cockroaches venture out at night to feed on a wide variety of organic materials, such as food waste, manure, and both plant and animal matter in various stages of decomposition. In many cases, foraging cockroaches may enter structures that are not properly sealed, often triggering complaints and calls for pest control services.
What's the concern?
Though they don't pose the same threats to public health and indoor air quality as do German cockroaches (Blatella germanica), oriental and Turkestan cockroaches are often targeted by both indoor and outdoor insecticide applications, usually in the form of liquid or aerosol sprays. Perimeter protection services, where liquid formulations are regularly sprayed around building exteriors to provide repellency or residual toxicity for pests that may invade the structures from outside, are especially common for cockroaches. Such programs may be largely ineffective, however, since without exclusion measures, insects can still invade, only to die within buildings.
In addition, many insects have developed resistance to commonly used active ingredients, especially pyrethroid insecticides, due to widespread exposure in the environment and limited variety in pesticide products. Finally, such programs may be prohibited or discouraged because of regulations enacted to protect the environment and surrounding communities (see “Ask the Expert” on page 6 of the Summer 2019 issue of the Green Bulletin). For instance, public schools in California provide challenging settings for traditional perimeter protection since spray applications require special posting, notification, and reporting.
For all these reasons, professionals in California may consider alternatives to perimeter spray programs in order to provide effective control of these nuisance cockroaches for their customers.
Gel baits have proven very effective when used to control German cockroaches indoors, but can they be used for outdoor species? Furthermore, the use of baits within self-contained, tamper-proof bait stations is exempt from the notification and posting requirements associated with public schools.
Oriental and Turkestan cockroaches are most active during the warm summer and early autumn months, when conditions in many parts of California are extremely harsh, with very high daytime temperatures and very low relative humidity. Can baits hold up under those conditions and remain attractive, edible, and palatable to cockroaches?
Laboratory and Field Trials
In order to measure the potential efficacy of exterior summertime applications, new groups of cockroaches were provided bait deposits dried on a lab bench for seven days. This drying period resulted in significant water loss from gel baits, rendering them quite hard and brittle. Nevertheless, exposure to dried baits also resulted in widespread mortality, with most groups of cockroaches exhibiting mortality at or near 100% after 14 days. In some cases, very little bait was consumed, suggesting that contact rather than ingestion contributed to mortality. These results suggest that many different professional cockroach baits are attractive to Blatta species, even when insects have access to alternative food and water sources, and that bait deposits can effectively kill cockroaches even when they are dried.
At these sites, three different bait products (Table 1) were applied within separate large (100-foot radius) treatment areas and compared to areas that were left untreated in terms of cockroach density, as measured by sticky traps placed out overnight once a month for one year. Bait was applied during periods of cockroach activity within locked rodent bait stations (Figure 4) or within subsurface utility ports (four bait placements of 1 g to 3 g per treatment area as needed monthly, according to observed cockroach density). Six applications were made at the Mendocino County site, while only two applications were made at the Riverside County site.
Control was achieved at both sites, but the population crash observed in Mendocino County was dramatic (Figure 5): 90% fewer cockroaches were trapped just one month after the baiting program began. Trap catches also fell by up to 50% in untreated plots. We believe these widespread decreases were driven by secondary and even tertiary mortality caused by cannibalism of bait-intoxicated cockroaches or scavenging of bait-killed cockroaches. This suggests that cockroaches in our field trial moved from one treatment area to the next, meaning that Turkestan cockroaches may venture more than 100 ft from harborages during foraging. Cannibalism was commonly observed in our overnight trapping programs, with trapped cockroaches dismembered and consumed by others (Figure 6).
At the Riverside County site, populations were smaller, foraging activity was lower, and population density within untreated plots remained high throughout the study. The one-year period ended at this site in October 2018, and preliminary data show that baits effectively reduced the population by 80% to 90% as compared to no treatment at all (Figure 7).
What did we find?
The results of this project suggest that bait-only programs can be very effective when used against oriental and Turkestan cockroaches in California, even when populations are large. The products tested were all very effective. We believe bait-only programs represent important alternatives to perimeter sprays and should be strongly considered when seeking to minimize exposure risk within IPM programs and when serving sensitive sites such as schools and child care centers, hospitals, municipal properties, and public outdoor spaces.
[Article originally published as "Outdoor baiting programs for cockroaches can provide excellent control" in the Summer 2019 issue of the Green Bulletin. For more on cockroaches and their management, see our Pest Notes: Cockroaches.]
/h2>/h2>/h2>/div>- Author: Michelle Leinfelder-Miles
UC Cooperative Extension has augmented efforts to monitor armyworm populations in rice fields since 2015 when we observed large populations earlier in the year (June) than previously observed. Here in San Joaquin County, we began monitoring in Delta rice fields a couple weeks ago. We are cooperating with rice farm advisors in the Sacramento Valley to get a more comprehensive assessment of the populations. Figure 1 shows moth counts from last week. The Delta count is the single orange data point at about 36 moths/day. Compare that to the Sacramento Valley where there have been similarly high moth catches in Colusa and Glenn counties.
These counts illustrate that it is important to be monitoring fields for worm feeding. The UC IPM guidelines for monitoring and treatment are excerpted below. In general, at the foliar stage, if half of the sampled plants have at least 25 percent defoliation from feeding, and worms are visible, then treatment is probably warranted. At the panicle stage, if 10 percent of the panicles are damaged and worms are present, then treatment may be warranted.
Armyworm larvae will grow to full size and pupate in about 3 to 4 weeks. That said, it is important to monitor fields now and later in the summer in case the current generation reproduces and a new generation develops when panicles are present.
In 2016, UC Cooperative Extension worked with the California Rice Commission to get an emergency approval for the use of Intrepid 2F (methoxyfenozide) in affected rice counties, including San Joaquin County. The 2017 application has not yet been approved, so we do not currently have this product available for rice. Please see the UC IPM guidelines for a list of registered products. I will provide an update on future moth trapping counts and product approvals as the information becomes available.
From UC IPM: Rice Armyworm Monitoring and Treatment
Foliar Injury: Monitor for foliar injury from panicle differentiation to heading by looking for signs of armyworms feeding on leaves. Once you begin to observe injury, start taking samples twice a week until grain start maturing or larvae are no longer present. To sample, choose a part of the field where you have observed injury. Select a plant at random and pull it up or move all the surrounding foliage away and check for defoliation. Check the plant from the top of the leaves to the base of the plant and the water surface for armyworms. Determine if 25% or more of the foliage has been removed by armyworms; also note if you find armyworms on neighboring weeds or rice plants. Record your observations on a monitoring form. Repeat this procedure every 5 to 10 feet (1.5–3 m) across a transect until 10 plants have been examined. Move to a different part of the field where feeding is evident and examine 10 more plants in the same manner. Repeat this procedure at several areas of the field until you are confident that you have an estimate of the average field condition.
Panicle Loss: Monitor for panicle loss after panicle emergence by checking for entire panicles or parts of panicles that have turned white; these indicate armyworm feeding. Be sure to differentiate this injury from stem rot, which may kill the entire panicle and darken the stems. Once you begin to observe armyworm injury to the panicle, take samples twice a week to determine the need for treatment. Use a sampling ring made of plastic tubing that encloses 1 square foot. Select your sampling sites in parts of the field with white panicles. Drop the ring at your side without looking. Examine all the plants within the ring down to the water level for armyworms; at the same time check for stem rot. Record the number of panicles and the percentage of them that are white and the presence or absence of armyworms within the ring. Move on 5 to 10 feet and repeat the procedure until 10 samples have been taken. Move to another area of the field with signs of panicle injury and take 10 more samples. Repeat the 10-sample procedure until you feel that you have a good estimate of the field condition.
Treatment Decisions: From panicle differentiation through heading, treat for foliar damage only in those areas of the field where 5 or more of the 10 samples taken have over 25% defoliation and armyworms are present on the plants. If you observe a few or no armyworms, come back at night to check for the larvae, which are more active after dark. Do not treat if armyworms are not present, especially during late August, because they have probably completed development.
From panicle emergence to grain maturity, treat for panicle loss if 10% of the panicles in the area sampled are damaged and armyworms are observed. If armyworms are not observed but panicle loss is 10% or more, check for the larvae at night. If larvae are not found, do not treat because they have probably pupated and will do no further damage. Limit treatments to those areas of the field with economic damage.