Pest Control Food Safety | Field Rodent Control

Pest Control Food Safety | Field Rodent Control

BorderLine Uses for Rats & Mice | Monitoring Fields with NoTox Blocks
Controlling Voles Overview | BorderLine Uses for Voles | Controlling CA Voles Artichoke Fields

Monitoring & Controlling Rodent Intrusion

Field rodents are vectors for disease and contamination including E. coli., and threaten food safety.

Pest Control Food Safety | Field Rodent Control

Rodent intrusion

“In 2006, spinach contaminated with E. coli resulted in the death of 3 people and over 200 illnesses. The contaminated spinach was traced to a field in California. In 2007 produce industry representatives developed safety guidelines (known as the [Food Safety] Metrics) for lettuce and other leafy green crops. The Metrics addressed intrusion and crop contamination by wildlife and livestock. Although not specifically mentioned in the Metrics, rodents are treated by growers and buyers as suspects in the food-borne illness complex…” Many rodent control programs are ad-hoc, and inconsistently monitored or maintained, sometimes resulting in ineffective practices in leafy greens and other vegetable crops.

“… The Food Safety Metrics require periodic monitoring of animal activity in and around crop fields, but many [grower associations or packer/shippers] lack specific guidelines on how to monitor for rodents.”

During a recent project (*) 10 iceberg lettuce and 4 spinach fields in the Salinas Valley region of Monterey County were surveyed from May 2009 through June 2010. Specific objectives of this project were to:

  1. identify the issues and requirements growers must address, particularly those demanded by buyers of leafy green crops, regarding rodent intrusion in leafy green crops;
  2. develop monitoring strategies and related training materials, and
  3. identify the rodent species that live in and around leafy green crops

Study Highlights / Findings:

  • Mice were the most abundant rodent species found at 50% of sample sites monitored, followed by voles at over 7% of sites. (p.10)
  • On average, three times (3X) as many rodents were found at “wild borders”, as “in-crop”.
    • This suggests that these riparian buffer areas should be one of the focus areas to prevent rodent migration into adjacent fields.
  • Wax monitoring blocks performed the best: accurately detecting rodent activity and intrusion risk over six times (6X) more often than snap traps.
  • We recommend regularly controlling rodents along the field edge outside of the crop.

* 2010 study titled: FOOD SAFETY AND RODENT CONTROL IN LEAFY GREEN CROPS, completed by Salmon, Terrell. P., Gorenzel, W.P., Newman, P.D. and Lima, L., Department of Wildlife, Fish and Conservation Biology, University of California San Diego County Cooperative Extension, Unpublished final report. California Department of Food and Agriculture, Sacramento, California. Contract No. 09-0220. June 30, 2010 pp. 1-38. Used with permission.

BorderLine® Usage Guide
for Rats & Mice – Outdoors
(Commensal Rodent Control)

Pest Control Food Safety | Field Rodent Control

Restricted Use Pesticide

Registered in: AZ & CA

READ THE LABEL and follow all use directions and precautions. Only use for sites, pests, and application methods specified on this label.

Apply bait in locations out of reach of children, pets, domestic animals, and non-target wildlife, or in tamper-resistant bait stations.

Pest Control Food Safety | Field Rodent Control

Left to right: Non-crop Field border, Railroad right-of way, Fenceline placement

Note: Bait stations are mandatory for outdoor, above-ground use. Tamper-resistant bait stations must be used if children, pets, non-target mammals, or birds may access the bait. These stations must be resistant to destruction by dogs and children under six years of age, and must be used in a manner that prevents such children from reaching into bait compartments and obtaining bait. If bait can be shaken from stations when they are lifted, units must be secured or otherwise immobilized. Even stronger bait stations are needed in areas open to hoofed livestock, raccoons, bears, other potentially destructive animals, or in areas prone to vandalism.


This weather-resistant product may only be used to control Norway rats, roof rats and house mice in outdoor non-crop areas, such as fence lines, gullies, ditches, railroad rights-of way, garbage dumps, landfills and recycling facilities. This product must not be applied directly to food or feed crops, but may be applied on border areas and buffer strips adjacent to crops. All placements must be in tamper-resistant bait stations or placed deeply into rat burrows. Do not broadcast bait. Do not apply product if heavy rain or flooding would result in contaminating aquatic environments.


This product can only be used to control Norway rats, roof rats and house mice in and within 100 feet of man-made structures constructed in a manner so as to be vulnerable to commensal rodent invasions and/or to harboring or attracting rodent infestations. Examples of such structures include homes and other permanent or temporary residences, food processing facilities, industrial and commercial buildings, trash receptacles, agricultural and public buildings, transport vehicles (ships, trains, aircraft), docks and port or terminal buildings, and related structures around and associated with these sites. Fence and perimeter baiting beyond 100 feet from a structure, as defined above, is prohibited. Do not sell this product in individual containers holding less than 4 pounds of bait. Do not place near or inside ventilation duct openings. Do not contaminate water, food, feedstuffs, food or feed handling equipment, or milk or meat handling equipment. Do not apply directly to food or feed crops. Do not broadcast bait.


House Mice: Apply ¼ to ½ ounce of bait (1-2 level tablespoons) per placement, usually spaced 8 to 12 feet apart. Larger amounts (up to 2 ounces) may be needed at points of very high house mouse activity. Maintain a constant supply of fresh bait for 15 days or until signs of house mouse activity cease.

Rats: Apply 4 to 16 ounces per placement, usually spaced 15 to 30 feet apart. Maintain a constant supply of fresh bait for 10 days or until fresh signs of rat activity cease. This product may be applied to active rodent burrows to control Norway rats, and roof rats within or beyond 100 feet of buildings and man-made structures, provided that infestations of these rodents have been confirmed. Bait must be placed no less than 6 inches into active Norway/roof rat burrows. Because Norway/roof rat infestations may occur in areas farther than 100 feet from buildings and man-made structures when the rodents have ample supplies of food and cover, efforts should be made to remove food trash, garbage, clutter and debris. Do not broadcast bait.


Replace contaminated or spoiled bait immediately. Wearing waterproof gloves, collect and dispose of all visible dead animals and leftover bait, as well as any bait that has become accessible to non-target animals. To discourage re-infestation, limit sources of rodent food, water and harborage as much as possible. If re-infestation does occur, repeat treatment. For a continuous infestation, set up permanent bait stations and replenish bait as needed.

Pest Control Food Safety | Field Rodent Control

NoTox Monitoring Blocks
Usage Guide
(for “green” monitoring of field rodent activity)

Pest Control Food Safety | Field Rodent Control

NoTox is not a pesticide. NoTox contains no active ingredient and can be used anywhere that a non-toxic monitoring block could prove useful. The following are suggested treatment areas where rodent intrusion is known to cause problems.

Selection of Treatment Areas:  These NoTox™ blocks may be used to monitor activity of field rodents including: ground squirrels, mice, rats and voles (microtus spp.) in and around agricultural crops, food processing centers, commercial, industrial, agricultural and public buildings, non-crop areas, recreational sites and parks. It may also be used in transport vehicles and in and around related port or terminal buildings, as well as residential areas.

Pest Control Food Safety | Field Rodent Control

Inspecting fields for rodent intrusion

Application Directions: Determine where field rodents are likely to be found: such as in or beside burrows, along fencelines, ditchbanks, gullies, irrigation canals, railroad rights of way, and other “wild borders”, as well as along walls, by gnawed openings, in or beside burrows, in corners and concealed places, between floors or walls or other locations where rodent activity or their signs.

Exterior placements / “T” pipe and other bait stations: such as along field borders

Secure 2-4, 20g NoTox blocks on a vertical securing wire within the bait station.

Interior placements: such as agricultural buildings and storage sheds

Mice: Secure one 20g block every 8 to 12 feet.
Rats: Secure one 20g block every 15 to 30 feet.

Monitoring: Inspect bait regularly for signs of rodent activity. If signs of gnawing or eating of bait are noted, try to determine the rodent species present. This NoTox bait should then be replaced with a properly-labeled toxic bait such as BorderLine® (a restricted-use pesticide) until no new signs of rodent activity occur. Replace moldy or spoiled bait immediately.

Storage and Disposal

Store in tightly sealed original container in a cool, dry place to preserve freshness. This product is non-toxic and may be disposed of in the same manner as other food products.

Overview – Controlling Voles

Pest Control Food Safety | Field Rodent Control

California Vole
Photo by Wesley Gordon

Pest Control Food Safety | Field Rodent Control

Emerging leafy greens field

Six species of voles of the genus Microtus occur in California. The California vole (Microtus californicus) is the most widespread vole in the state, found along nearly the entire length of the coast range, and is responsible for the majority of damage to vegetables.

These voles are grizzled brownish with scattered black hairs on their backs; and gray hairs below, with hairs often white-tipped. They possess a relatively long, two-colored tail and pale feet, and can reach 5 to 8 inches in length from head to tail. They typically weigh from 1 1/2–3 1/2 oz (42–100 g).

Voles are prolific breeders with females maturing in 5 to 6 weeks and having 5-10 litters per year. Litter size ranges from three to six. However, voles seldom live past a year.

Damage & Disease Transmission to
Vegetables / Artichokes

Voles feed on a variety of grasses, herbaceous plants, bulbs, and tubers. They usually consume bark and roots of trees, only in the fall or winter, when other food sources are less available. In California, they cause notable damage on the following vegetables: artichoke, beet, Brussels sprouts, cabbage, carrot, cauliflower, celery, lettuce, turnip, sweet potato, spinach, and tomato.

California voles are known carriers of the hantavirus and probable carriers of other diseases as well. Vegetable growers are concerned that California voles, along with slugs & snails, can also transmit, through gnawing and saliva, E. coli. and other bacteria.1


Paraphrased from UC-Davis Pest Notes: Authors: T. P. Salmon, Wildlife, Fish, and Conservation Biology, UC Davis; and W. P. Gorenzel, Wildlife, Fish, and Conservation Biology, UC Davis. Editor: B. Ohlendorf.

BorderLine® Usage Guide for Vole Control

Pest Control Food Safety | Field Rodent Control

Meadow vole                            Pine vole

Pest Control Food Safety | Field Rodent Control

Restricted Use Pesticide

Registered in: AZ & CA

Border Areas & Buffer Strips Adjacent to Crops (Vole Control)

Pest Control Food Safety | Field Rodent Control

Pest Control Food Safety | Field Rodent Control

Pest Control Food Safety | Field Rodent Control

Pest Control Food Safety | Field Rodent Control


For control of only voles in commercial nurseries, tree and forestry plantations, Christmas tree farms, and border areas and buffer strips adjacent to crops (within 100 feet of the edge of the cropland). This product must not be applied directly to food or feed crops except as specified above. Do not apply within 50 feet of any body of surface water or where raptors are actively feeding on voles. Do not allow animals to graze in treated areas. Do not use hay cut after application for feed or bedding. To avoid exposing non-target organisms, follow the instructions in the "Pesticide disposal" section to insure proper clean-up of any bait for reuse or disposal. Apply only by hand spot baiting and ground broadcasting. Do not apply aerially. In Colorado, Florida, New York and Vermont, only apply by "Hand Spot Baiting." In Florida, only use this product where Pine voles are known to occur and only apply by “Hand Spot Baiting.”


Before application, locate vole trails, runway systems and harborage areas to be treated. Hand spot baiting: Place 1-1/2 ounces (6 tablespoons) of bait in each active hole, trail or runway (do not exceed 10 lbs. per acre). Cover each placement with grass or shingle to avoid exposing non-target organisms, or place bait in a tamper resistant bait station.

Pest Control Food Safety | Field Rodent Control

Left to right: Broadcast spreader, Rodent intrusion, "T" pipe bait station

Ground broadcast baiting: Using a commercial spreader, uniformly apply 10 lbs. per acre. If populations are high, make a second application 1 - 2 months after the first. In states east of the Mississippi River, infestations of pine vole (Microtus pinetorum) may require higher application rates of 20 lbs. per acre. The maximum application rate is 40 lbs per acre per year for Pine voles, and 20 lbs. per acre per year for other voles.

Commercial Nurseries, Christmas Tree Farms, Tree & Forestry Plantations (Vole Control)

Pest Control Food Safety | Field Rodent Control

Pest Control Food Safety | Field Rodent Control

Pest Control Food Safety | Field Rodent Control

The same directions shown under Border Areas & Buffer Strips  Adjacent to Crops apply to the Commercial Nurseries, Christmas Tree Farms, Tree & Forestry Plantations segments shown above.

Ornamental Turf Areas, Ornamental Flower & Shrub Gardens, Golf Courses, Parks & Lawns

Pest Control Food Safety | Field Rodent Control Pest Control Food Safety | Field Rodent Control

Special Instructions:
Hand Spot Bait only:
Do not apply by aerial or ground broadcast. For control of only voles (Microtus spp.) in lawns, golf courses, parks, other ornamental turf areas, ornamental flower and shrub gardens. Place 1/2 to 1 ounce, (2 to 4 tablespoons,) of bait in each active hole, trail or runway in areas where voles have been observed or are known to forage. If non-target animals/birds are present, place bait in tamper-resistant bait stations. Also apply under tarps used to provide winter protection for turf areas. Apply only one bait spot per trail or runway. If additional vole control is needed, a second application may be made 1 to 2 months after the first application. The maximum application rate is 10 lbs per acre per application, and 20 pounds per acre per year. Do not apply to golf courses or turfgrass areas in the state of California.

Rozol® Pellets for the control of California Voles (microtus californicus) in artichoke fields [24(c) CA 060006 label]

Pest Control Food Safety | Field Rodent Control

Photo courtesy of Lionel Handel - Kleen-Globe Ag Service

Rozol® Pellets (EPA Reg. No. 7173-151) are registered for use only within the state of California for the control of California voles (Microtus californicus) in artichoke fields. When used for this purpose, Rozol Pellets are a Restricted-Use Product, and may be sold and used only by Certified Applicators, or persons under their direct supervision, and only for uses covered by the Certified Applicator’s certificate.

In order to use this product for the control of California Voles, you must have a 24(c) Rozol Pellets label in your possession at the time of application.

Helpful Tips/Application Directions

APPLICATION DIRECTIONS: Use Rozol Pellets for the control of California Voles (microtus californicus) in artichoke fields [24(c) label] as an alternative to Chlorophacinone Treated Artichoke Bracts only during the period from October through March if artichoke bracts are not available. Place about 3 to 5 grams of bait (approximately 1 level tablespoon) per artichoke plant, on bare ground in infested areas. Apply bait near vole burrow openings or runways located between artichoke plants. Be careful to place bait so that it does not directly contact any part of the artichoke plant. If necessary, make second and third applications at 21 day intervals. Do not exceed three applications in made at minimum 21 day intervals per regimen. Repeat the treatment regimen after 60 days if needed. Do not exceed 3 applications at minimum 21 day intervals. Do not apply this product by any method not specified on this label. Do not broadcast bait. To reduce the potential for exposure to non-target animals and birds, do not apply this bait for a period of 30 days before or after chopping or cut-back of artichoke plants.

ENDANGERED SPECIES CONSIDERATIONS: NOTICE: It is a Federal offense to use any pesticide in a manner that results in the death of an endangered species. Use of this product may pose a hazard to endangered or threatened species. Before applying this product, applicators must obtain information regarding the occurrence of endangered species and use limitations for this product. In California, contact your County Agricultural Commissioner or refer to the Department of Pesticide Regulation’s PRESCRIBE Internet Database.

ENVIRONMENTAL HAZARDS: This product is toxic to fish, birds and wildlife. Do not apply directly to water, to areas where surface water is present or to intertidal areas below the mean high water mark. Do not contaminate water by cleaning of equipment or disposal of wastes. Run-off may be hazardous to aquatic organisms in water adjacent to treated areas.

See entire label. It is the responsibility of the user to read and follow all label directions.

Specimen Labels and Safety Data Sheets

Brand Labels (Eng) SDS (Eng) Labels (Spa) SDS (Spa)
BorderLine Labels (Eng) SDS (Eng) Labels (Spa) SDS (Spa)
NoTox Labels (Eng/Spa) SDS (Eng) Labels (Eng/Spa) SDS (Spa)
Rozol Vole Bait (in Artichoke fields) Specimen Label SDS (Eng) N/A SDS (Spa)