Fumigation | California ground squirrel
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Fumigation is generally most effective when precipitation is occurring (late winter through spring). However, it can also be effective anytime sufficient soil moisture is available. Soil moisture is needed for the toxic gases to build up to lethal concentrations. Dry soil tends to be too porous to allow toxic gases to be contained at adequate concentrations. Fumigants may be less effective in sandy and rocky soils, given high porosity (sandy soils) or frequent cracks (rocky soils) in the soil.
Several fumigants/devices can be used for ground squirrel management. Jump to: Fumigation in Urban Areas Fumigation is generally problematic in urban areas because of the potential for toxic gases to leak into buildings from burrow systems below. However, if used far enough away from structures (read the label of the fumigant for specific criteria of where they can be used), some burrow fumigants can be safely and effectively used. |
Aluminum Phosphide
Aluminum phosphide is an excellent material for controlling California ground squirrels and can be considerably cheaper than other fumigation options. Past studies show 97–100% control in burrows systems treated with aluminum phosphide. The material is distributed in the form of tablets and pellets, which release phosphine gas when exposed to moisture in the burrow system. The gas is inhaled by the ground squirrels and then enters the bloodstream. This product will also control flea populations associated with California ground squirrels and their burrow systems, providing added utility that most other management tools lack.
It is important to follow the directions on the label to ensure the safety of the applicator.
Restrictions
Aluminum phosphide is a restricted use material and requires a restricted use permit to purchase and use. You must also be a Qualified Applicator or be supervised by a Qualified Applicator to use this material. Homeowners and other individuals in residential areas must possess a professional pesticide applicator certificate or license to use aluminum phosphide.
The use of aluminum phosphide is heavily restricted by location and proximity to people and domestic animals:
It is important to follow the directions on the label to ensure the safety of the applicator.
Restrictions
Aluminum phosphide is a restricted use material and requires a restricted use permit to purchase and use. You must also be a Qualified Applicator or be supervised by a Qualified Applicator to use this material. Homeowners and other individuals in residential areas must possess a professional pesticide applicator certificate or license to use aluminum phosphide.
The use of aluminum phosphide is heavily restricted by location and proximity to people and domestic animals:
Aluminum Phosphide use is permitted ONLY when: |
Aluminum Phosphide is PROHIBITED: |
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All permitting and reporting is similar to that required for other federally restricted pesticides with the added requirement of a fumigation management plan. This plan must be written by any applicators who intend to use aluminum phosphide, in accordance with the label instructions outlining the content of the plan. It describes the steps necessary to carrying out a safe and effective management plan.
Application
For application, 2-4 tablets or 10-20 pellets are placed as far into the burrow as possible. The burrow must be sealed with crumbled-up newspaper, or a similar material, and then covered with soil. This prevents the gas from escaping through the burrow entrance. Because it is difficult to tell which burrow openings are connected to others, all active burrow openings should be treated and sealed. Only treat active burrow systems, as abandoned California ground squirrel burrow systems are often used by other species (e.g., San Joaquin kit fox, blunt-nosed leopard lizard [Gambelia sila], and burrowing owl). Approximately 48 hours after the initial treatment, the treatment area should be checked for open burrows. These re-opened burrows should be treated again.
Application
For application, 2-4 tablets or 10-20 pellets are placed as far into the burrow as possible. The burrow must be sealed with crumbled-up newspaper, or a similar material, and then covered with soil. This prevents the gas from escaping through the burrow entrance. Because it is difficult to tell which burrow openings are connected to others, all active burrow openings should be treated and sealed. Only treat active burrow systems, as abandoned California ground squirrel burrow systems are often used by other species (e.g., San Joaquin kit fox, blunt-nosed leopard lizard [Gambelia sila], and burrowing owl). Approximately 48 hours after the initial treatment, the treatment area should be checked for open burrows. These re-opened burrows should be treated again.
Aluminum phosphide tablets may spontaneously combust if they come into direct contact with water. Never pour water down the burrow system before or after application. The soil in the burrow must be sufficiently moist without the addition of extra water. Soil that is not moist enough to evolve toxic levels of phosphine gas will also be too dry to contain the toxic gases within the burrow system. To determine if the soil is moist enough for effective application, dig down to the level of the burrow system, grab a handful of loose soil, and ball it up in your hand. If the soil holds its shape, it is moist enough for application; if the ball falls apart, the soil is too dry for the application to be effective and another management option must be considered. If the soil is obviously moist, this is not necessary.
Gas Cartridges
Fumigation using gas cartridges is somewhat less efficacious. Although studies have shown that the efficacy varies, it can be as high as 75%. Management of California ground squirrels using gas cartridges is more expensive than aluminum phosphide. Costs, excluding labor for gas cartridges are ~$2.00/burrow opening vs. ~$0.18–$0.36/burrow opening for aluminum phosphide. The management cost is about 2.5 times higher for gas cartridges than for aluminum phosphide when including both labor and material costs. However, gas cartridges are not a restricted use material and can be used without a pesticide applicator license or certification. The active ingredients of gas cartridges are sodium nitrate and charcoal; some also contain sulphur. This creates carbon monoxide (and sulphur dioxide if the cartridge contains sulphur) when ignited. This toxic gas displaces oxygen in the animals’ bloodstream and results in death by asphyxiation. Gas cartridges can flare up and cause fire hazards in vegetation, so caution must be taken when using them, particularly in dry conditions to avoid wildfires and injuries to applicators.
Restrictions
Gas cartridges cannot be used to control ground squirrels in or under buildings and must be applied a safe distance from all structures. This distance is specified by individual products. Please consult all pesticide labels for restrictions before considering their use.
Application
Instructions for the use of gas cartridges may be product specific. It is very important to consult the label for use. Generally to use a gas cartridge, puncture the cartridge cap end at marked points with a nail or other sharp instrument. Insert a fuse into the hole created by the nail. Place the cartridge into an active burrow entrance with the fuse pointing towards the interior of the burrow. Light the fuse and push the cartridge down into the burrow with a shovel handle. Immediately seal and tightly pack the burrow opening with soil. Multiple entrances to the same burrow system do not necessarily need to be treated separately, but it is important to seal any additional openings. Use the smoke escaping from the burrow to identify these entrances. This can lower the cost of gas cartridge applications since fewer burrow openings may need to be treated. Larger burrow systems, however, may require two or more cartridges. There are no guidelines for estimating burrow size. Estimating burrow size should be based on general appearance of the burrow system and user experience.
Restrictions
Gas cartridges cannot be used to control ground squirrels in or under buildings and must be applied a safe distance from all structures. This distance is specified by individual products. Please consult all pesticide labels for restrictions before considering their use.
Application
Instructions for the use of gas cartridges may be product specific. It is very important to consult the label for use. Generally to use a gas cartridge, puncture the cartridge cap end at marked points with a nail or other sharp instrument. Insert a fuse into the hole created by the nail. Place the cartridge into an active burrow entrance with the fuse pointing towards the interior of the burrow. Light the fuse and push the cartridge down into the burrow with a shovel handle. Immediately seal and tightly pack the burrow opening with soil. Multiple entrances to the same burrow system do not necessarily need to be treated separately, but it is important to seal any additional openings. Use the smoke escaping from the burrow to identify these entrances. This can lower the cost of gas cartridge applications since fewer burrow openings may need to be treated. Larger burrow systems, however, may require two or more cartridges. There are no guidelines for estimating burrow size. Estimating burrow size should be based on general appearance of the burrow system and user experience.
As with all other burrow fumigants, be sure that soil moisture is adequate to ensure maximum effectiveness. Approximately 48 hours after the initial treatment, the treated area should be checked for open burrows; any re-opened burrows should be treated again.
Carbon Monoxide
Several carbon monoxide-based devices are currently available for use. While some of these devices are effective, they are also expensive. The expense of purchasing one of these devices would be impractical for homeowner purposes. However, professional pest control companies may offer carbon monoxide-based devices as an option.
Carbon monoxide devices include:
Pressurized Exhaust Rodent Controller (PERC)
Carbon monoxide devices include:
Pressurized Exhaust Rodent Controller (PERC)
- Uses a small engine to create exhaust rich in carbon monoxide, which is cooled and stored in a compressor tank before being injected into the burrow system
- Most extensively tested
- Effective for California ground squirrel control (66%-100% efficacy) and Belding’s ground squirrel (71% -81% efficacy) in moderately moist to moist soil conditions
- Tested fairly well in dry soil conditions (66% efficacy) compared to what would be expected for other fumigation options
- Can be used to treat multiple burrow systems simultaneously, thereby increasing the speed with which an area can be treated. A single applicator can operate 3-4 probes at a time. If using the 6-probe system, two people are needed to operate.
- Typical application time of 3-6 minutes, depending on the size of the burrow system
- Trial results did not indicate any effectiveness for California ground squirrel (based on a single trial conducted by UC Extension personnel)
- Most other available devices have yet to be tested by independent evaluators using replicated trials