Pest Management Guidelines - treesandshrubs
Pest Management Guidelines
A Cornell Cooperative Extension Publication

  
Cornell Guide for Pest Management of Trees and Shrubs

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5 Vertebrate Pest Management

5 Vertebrate Pest Management

Contents

5 Vertebrate Pest Management 1

5.1 Integrated Pest Management (IPM) 1

5.2 Control of Rodent Damage to Nursery and Landscape Plants. 1

5.2.1 Rodent Control in Field Situations. 1

5.2.1.1 Cultural Practices. 1

5.3 Repellents for Deer and Rabbits. 1

5.4 Nonchemical Wildlife Damage Management Alternatives. 2

5.4.1 Fencing. 2

5.4.2 Other Methods. 3

5.5 Rodent Control in Buildings and Other Structures. 3

5.5.1 Pest Species. 3

5.5.2 Feeding Behavior 3

5.5.3 Determining the Presence of Rodents. 3

5.5.4 Long-Term Population Suppression. 3

5.5.5 Rodenticides for Structural Use. 3

5.5.5.1 Prebaiting. 4

5.5.5.2 Bait Placement 4

5.5.5.3 Bait Boxes. 4

5.5.5.4 Paraffin Bait Blocks. 4

5.5.5.5 Traps. 4

 

 

5.1 Integrated Pest Management (IPM)

It must be realized that there is no "magic pill" for pest control-no single, simple remedy that can be relied on to solve rodent problems in a sustainable way. Rodent control must be considered in terms of the environment in which the pest is active. Control activities must have as an overriding principle the biology and behavior of the animal in concert with its whole environment. Integrated pest management (IPM) is a holistic, decision-making system-a process in which all interventions are brought to bear on a pest problem with the goal of providing the most effective, economical, and safe program as possible. In short, IPM is a process for determining if, where, when, and what pest management intervention(s) are needed or justified.

 

5.2 Control of Rodent Damage to Nursery and Landscape Plants

*Zinc phosphide reduces trunk girdling by voles on nursery stock. Acute toxicants such as *zinc phosphide should not be used more than once every six months, preferably only once a year. When acute toxicants are used repeatedly in the same area, local vole populations may develop an aversion and become bait shy. Several formulations are available.

 

5.2.1 Rodent Control in Field Situations

Two species of voles damage trees and shrubs in New York nurseries. Meadow voles are found throughout the state and inhabit old fields, roadsides, and other areas with sod cover. Pine voles are a problem in the Hudson River Valley, especially in a five-county area (Dutchess, Orange, Putnam, Ulster, and Westchester). Nurseries in these counties may have both species present and could experience damage to trees during severe weather or when other food sources become unavailable.

 

The contrasting living habits of meadow and pine voles have important implications for their detection and control. Meadow voles usually live on the surface of the ground. Runways 1 to 2 inches wide through the vegetation, often with droppings and plant cuttings 1/4 to 1/2 inch long, are good indications of their presence. Small openings to underground burrows are evidence of pine voles. Because meadow voles are active above ground and forage more widely than pine voles, broadcast baiting is more effective against meadow voles. When feasible, hand placement of baits in tunnels or under roofing shingles, slabs of wood, or similar protected bait stations is the preferred method for baiting pine voles. Timing often determines the success of a baiting program. The optimal time to apply baits is in the late fall.

 

For nurseries with recurring meadow vole problems, an annual fall baiting program using a *zinc phosphide-treated bait is strongly recommended (Table 5.2.1). Pelletized baits are available from commercial sources. Hand-broadcasting, tractor-operated seeding devices, and whirling-disc fertilizer spreaders are satisfactory means of application. Complete coverage of tree rows and adjacent areas is required for reliable control. However, do not apply baits to areas with bare ground, including vegetation-free cultivated strips under trees, because this may increase the chance of feeding and mortality of nontarget song and game birds. Always follow label directions for rates and observe all precautions. Because there is evidence that bait shyness may occur with repeated use of *zinc phosphide baits, a single, complete bait coverage of the site during a period of fair weather is desirable. Ideally, this should follow close mowing of sod areas.

 

 

Table 5.2.1. Pesticides for management of rodent damage to nursery and landscape plants

Material

EPA Reg. No.

Species

Application Rate

*Zinc Phosphide/Example Products

 

 

 

            *ZP Rodent Bait AG

12455-17

meadow and pine voles

6-10 lb./A

(other formulations available)

 

 

Machine baiting: Apply *Zinc Phosphide baits in the drip line of the trees by hand-operated or tractor-mounted fertilizer spreaders before leaves and grass mat down. Broadcast in nurseries during fall for control in winter months. Follow all label precautions and do not apply baits to bare-ground areas.

*Restricted-use pesticide; may be purchased and used only by certified applicators.

Important Note: Departmental Regulation 9500-4, Fish and Wildlife Policy, states that employees of the Cornell Cooperative Extension System, who are considered agents of USDA, must adhere to Section 7 regulations of the Endangered Species Act. Therefore, if a landowner or agent is aware that an endangered or threatened species, or its critical habitat, exists in an area where an agent’s guidelines are to be implemented, the U.S. Fish and Wildlife Service must be contacted for further information before any action can be taken. This regulation applies not only to pesticide use but includes any cultural practice or habitat modification that may affect endangered or threatened species. The USFWS address for Region 5 is Fish and Wildlife Enhancement, One Gateway Center, Suite 700, Newton Corner, Mass. 02158, telephone 617-965-9316. The Pesticide Management Education Program at Cornell University maintains an up-to-date catalogue of federally listed endangered and threatened species and their county distributions in New York State.

 

Because of their underground habits, pine voles can be difficult to manage. In nurseries with pine vole problems, the placement of toxic baits beneath previously established baiting stations can provide excellent control. It is important to establish one or two bait stations at trees with vole activity and have them in place long enough for the pine voles to establish a burrow system. Wooden slabs, tarpaper, shingles, or PVC-pipe bait stations provide suitable cover. As with meadow voles, late fall is the best time for rodenticide treatments.

 

The primary active ingredient available for field use in New York nurseries is *zinc phosphide. Frequent use of *zinc phosphide can lead to bait shyness (voles that consume sublethal doses no longer eat the bait). Rebaiting only results in reduced control and reinforces aversion to the rodenticide. Avoid using *zinc phosphide more than once every six months if possible, preferably only once per year. However, heavy pine vole infestations, as indicated by numerous burrows and fresh dirt castings at several adjacent trees, may require a second application of bait about two weeks after the first.

 

With all management efforts, it is also important to treat adjacent edges and weedy areas to avoid rapid vole reinvasion from nearby blocks. The most important consideration in timing a control program is to achieve the greatest vole reduction just before onset of severe winter conditions. Voles that remain alive in the nursery will survive under the protection of snow cover and can inflict considerable tree damage during winter months.

 

Monitoring nurseries for signs of vole activity enables growers to detect vole population increases. It also allows growers to evaluate the effectiveness of their baiting programs and the need for follow-up treatments. Apple activity indices can provide a reliable measure of rodent numbers and the potential for damage (see Cornell Information Bulletin 236, Wildlife Damage Management in Fruit Orchards, for additional information). Voles are notorious for sudden population irruptions every few years, and growers should monitor their nurseries even in years of low vole densities. Negligence may lead to rapid population increases and aggravated damage problems. Young trees (ranging in age from 1 to 15 years) are most susceptible to vole damage.

 

5.2.1.1 Cultural Practices

Although toxic baits offer reliable control and should be used where voles are abundant, cultural practices can reduce or even eliminate the need for rodenticides. Careful mowing, cultivation, and herbicide treatment will lower rodent numbers because voles require green, growing vegetation for survival and breeding. Efforts to reduce the density of ground cover will aid vole control. The meadow vole is especially vulnerable to close mowing of turf areas, and rotary mowers are much more effective than sickle-bar types for removing ground cover and thatch.

 

The use of an herbicide strip or cultivation beneath the trees and along the tree rows are cultural practices that can effectively eliminate meadow voles. In addition, wire guards will protect younger trees from meadow voles as well as rabbits; one-quarter-inch wire mesh has proven most satisfactory. Although close-mowing coupled with herbicide treatments or cultivation can provide outstanding meadow vole control, recent evidence indicates these management practices will reduce but not eliminate pine voles.

 

Important Note: *Zinc phosphide is a restricted-use pesticide and may be purchased and used only by certified applicators or someone under the supervision of a certified applicator.

 

5.3 Repellents for Deer and Rabbits

A variety of commercial repellents (Table 5.3.1) are available to reduce deer or rabbit browsing to nursery stock and ornamental plants. Repellents fall into two categories: those that produce an offensive taste when consumed and those that repel with a disagreeable odor. The effectiveness of repellents is extremely variable and is affected by factors such as deer or rabbit numbers, feeding habits, and environmental conditions. Repellents may be cost-effective for controlling wildlife damage when (1) light to moderate damage is evident, (2) small acreages are damaged, and (3) three or fewer applications will be needed for adequate control. If these three conditions are not satisfied, a grower may want to look at the cost-benefit ratios of electric fence designs or other alternatives.

 

Some damage must be tolerated with the use of repellents, even if browsing pressure is low. Repellents should be applied before damage is likely to occur and a feeding pattern is established. With taste-based materials, new plant growth should be covered every four weeks during susceptible stages. Repeat applications of odor-based repellents should be made every four to six weeks while plants are susceptible to damage (usually November through April).

 

Repellents should be applied when precipitation is not expected for 24 hours and temperatures will remain between 40 and 80 degrees F for that period. Applications should be thorough, covering all vulnerable portions of the plant. Hand spray applications may be cost-effective on small acreages, whereas machine sprays will reduce costs on large acreages if four or fewer applications are made each year. If the materials are compatible, spray costs may be reduced by adding repellents to a scheduled pesticide application.

 


Table 5.3.1. Commercial deer and/or rabbit repellents

Product

Mode of Action

Active Ingredient

Application Method

Manufacturer

Deer Away Pro Big Game

Odor/Taste

37% putrescent egg solids

Spray

Woodstream Corp.

Repellent Liquid

 

 

 

69 N. Locust St. Box 327

 

Lititz PA 17543

EPA Reg. No. 50932-6-74794

 

 

 

 

Hinder

Odor/Taste

13.8% ammonium soaps

Spray/Brush

Amvac Chemical Corp.

 

 

 

4695 Macarthur Ct.

EPA Reg. No. 5481-508

 

 

Newport Beach Ca 92660

Chew-Not

Taste

20% thiram

Spray/Brush

Nott Manufacturing Co.

 

 

 

P.O. Box 975

 

 

 

Coram, NY 11727

EPA Reg. No. 358-105

 

 

(914) 635-3243

Hot Sauce

Taste

2.5% capsaicin

Spray

Miller Chemical & Fertilizer Corp.

Animal Repellent

 

 

Box 333

 

 

 

Hanover, PA 17331

EPA Reg. No. 72-574

 

 

(717) 632-8921

Deer-Off Deer Repellent RTU

Odor/ Taste

0.78% egg solids

Spray

Woodstream Corp.

Repellent

 

0.001% capsaicin

 

69 N. Locust St. Box 327

 

 

0.001% garlic oil

 

Lititz PA 17543

EPA Reg. No. 67356-2

 

 

 

 

 

 

If browsing pressure is severe, a long-term damage management program should be implemented. Such a program should include potential habitat modifications, reductions in animal numbers, and an evaluation of exclusion alternatives.

 

5.4 Nonchemical Wildlife Damage Management Alternatives

A nursery owner can use a variety of nonchemical alternatives to reduce wildlife damage to nursery stock and ornamental shrubs. These techniques fall into several broad categories: exclusion, habitat modification, and wildlife population reductions. Although exclusion and habitat modification appear to be more expensive than population control, where possible, they may provide the greatest efficacy and longer-term relief from damage problems.

 

5.4.1 Fencing

Fencing is the most reliable exclusion technique for preventing wildlife damage to nursery stock (Table 5.4.1). Woven-wire designs are the most effective physical barrier to wildlife, with high-tensile woven-wire fencing providing the ultimate in protection and durability. Deer can be successfully eliminated from large areas (>50 acres) with an 8- to 10-foot woven-wire fence. The advantages of this design are its effectiveness and low maintenance requirements after construction. Disadvantages include the high initial cost and the difficulty in repairing damaged sections.

 

A variety of multi-strand, high-tensile, vertical or sloped, electric fence designs effectively exclude wildlife. Electric high-tensile fences may be complete physical barriers or, more commonly, may act as a behavioral deterrent. Deer can be excluded from crops with a 5- to 6-foot electric fence, even though they can easily jump over woven-wire fences of this height. The most frequent reasons why electric fences fail to prevent wildlife damage include the selection of an unsuitable fence design, failure to install fencing according to manufacturers' specifications, and inadequate maintenance. Electric fences will not exclude wildlife unless adequate voltage is constantly maintained on the wires. High-tensile electric fences are easily repaired and may cost half as much as 8- to 10-foot woven-wire designs. Disadvantages include frequent monitoring and the need for vegetation control to maintain shocking power.

 

Table 5.4.1. Sources of high-tensile fencing

Source

Distribution

Innovative Fence

Direct

4977 Ridge Chapel

 

Marion, NY 14505

 

(315) 926-7700

 

Kencove Fence

Direct

111 Kendall Lane

 

Blairsville, PA 15717

 

(800) 245-6902

 

Kiwi Fence Systems

Direct

1145 E. Roy Furman Hwy.

 

Waynesburg, PA 15370-8070

 

(412) 627-5640

 

Koppers Company

Agricultural outlets

Treated Wood Products Division

Room 950, Koppers Building

 

Pittsburg, PA 15219

 

(412) 227-2407

 

Tech-Fence Division

Local dealers

Multi-Tech Industries Inc.

 

P.O. Box 159

 

Marlboro, NJ 07746

 

(800) 431-3223

 

West Virginia Electric Fencing

 

Route 81, Box 3

 

Lindside, WV 24951

 

(304) 753-4387

 

The Wright Place

 

5051 Fowler Road

 

Reading, MI 49274

 

(517) 283-2654

 

 

5.4.2 Other Methods

Other physical barriers that can prevent wildlife damage include wire cages, plastic tubing, bud caps, and bird netting. Large-scale use of these materials may be uneconomical because of the labor required to apply and remove these barriers. Wire or plastic tree guards can be used to protect trees from trunk girdling by rodents or rabbits. The more expensive wire guards provide longer-term damage prevention.

 

Habitat modifications can make areas less suitable for nuisance wildlife. Damage prevention with cultural manipulations should begin with site selection and plant establishment. In nurseries, plowing or disking reduces vole populations, facilitates the establishment of the desired cover crop between rows, and simplifies future vegetation control. Removal of brush, stone piles, and nonmowable wet areas will reduce the attractiveness of sites to rodents and rabbits. Mowing in established plantings can reduce preferred wildlife foods, remove protective cover, enhance predation, and expose animals to severe weather conditions. Sites adjacent to crop lands should also be mowed to reduce pest numbers.

 

Wildlife population reductions may be necessary to reduce damage to tolerable levels. Snap-back or cage traps are effective for capturing small mammals. Larger rodents or carnivores can be caught with foothold or body-gripping traps. When trapping, care and experience are necessary to reduce captures of nontarget species. In more urban areas, live-capture cage traps are recommended to protect pets. In rural locations, shooting can be used to effectively remove problem animals.

 

A trapping license, small game license, or special permit may be required from the New York State Department of Environmental Conservation (DEC) for lethal control or transport of vertebrate pests. County and local laws vary in New York State, and some areas have trapping or shooting restrictions. Contact state and local officials before implementing any lethal or trapping and removal program for nuisance wildlife.

 

Reducing animal numbers by lethal methods may fail to provide long-term relief from damage. Where habitat conditions are suitable and exclusion is not attempted, most pest species will repopulate the site soon after control efforts have ceased, as animals will move into the control area from adjacent lands. Habitat modification and exclusion methods often require more initial effort and expense, but these techniques may provide longer-term damage prevention, especially when a few pest individuals can inflict substantial losses.

 

5.5 Rodent Control in Buildings and Other Structures

For an effective control program, you must know what species of mammals are involved. Correct identification is essential for selecting the proper damage management measures. Roof rats are rarely found in New York State and then only in a few locations (usually port cities). Norway rats, voles, and house mice are common throughout the state. Shrews may occupy structures but usually cause few problems.

5.5.1 Pest Species

The Norway rat and house mouse are abundant throughout the United States. They cause enormous economic losses by consuming and contaminating food as well as damaging property.

 

5.5.2 Feeding Behavior

Most rats and some mice are omnivorous, eating nearly any food, although each kind and population has its own preferences. The Norway rat is an avid consumer of human garbage, whereas the roof rat prefers more natural plant food, if available. They all feed to varying degrees on cereals, nuts, fruits, vegetables, invertebrates, fish, and even manure, depending on the habitat conditions.

 

Rats usually begin searching for food shortly after sunset. When hungry, or under crowded conditions, they may also be seen in daylight. Rats and mice may cache considerable amounts of solid food, which they may or may not eat later.

 

Prebaiting before a control program with a nontoxic bait can enhance later acceptance of rodenticides. The most acceptable bait is frequently a local food the rats and mice have already become accustomed to eating. Evidence of food preferences can be determined by carefully examining the infested area for damaged food items or scraps left behind.

 

5.5.3 Determining the Presence of Rodents

The habits of rodents provide numerous signs of their presence, including species, relative numbers and areas of activity. Evidence of rodents can be determined by one or a combination of factors. Species can best be identified after rats and mice have been trapped and closely examined.

 

·         Sounds: Gnawing on solid objects; clawing and climbing in walls, above dropped ceilings, and under cabinets; various squeaks; fighting noises.

·         Droppings: May be found along runways, near shelters, or other places rodents frequent.

·         Urine: Wet and dry rodent urine stains will fluoresce under ultraviolet light.

·         Smudge marks: May be found on pipes, beams against walls and outside edges of holes where dirt and oil from their fur is deposited where rodents frequently travel.

·         Runs: Smooth or worn areas may be found next to walls, along fences, under bushes and buildings.

·         Tracks: Footprints or tail marks may be found in dusty surfaces, sand, soft soil, and snow. The use of nontoxic tracking dust such as chalk powder or unscented talc will help determine the presence of rodents inside buildings.

·         Gnawing: May be indicated by wood chips around baseboards, doors, basement windows and frames, stored materials, around pipes in floors and walls, and wherever rats might try to enlarge a crack or enter a structure.

·         Burrows: Most commonly made by Norway rats in soft ground, particularly where burrow entrances can be concealed in low, dense vegetation or under concrete slabs, foundation walls, lumber, and piles of rubbish. Norway rats also burrow into soil floors in basements, warehouses, and animal quarters.

·         Visual sighting: Frequent observation of rats in daylight generally indicates a high population in the area. Mice may be active during the day or night.

·         Nests and food caches: Can sometimes be found when cleaning garages, attics, basements, and other storage places. Rodent species (i.e., squirrels and rats) often store food in attics of buildings.

·         Odors: Odors (resulting from deposits of fermenting rodent urine and feces and body oils) in a room may provide a clue to their presence.

·         Pet excitement: May occur when cats or dogs hear or smell rodents in some inaccessible spaces (e.g., in a wall); pets may sniff or scratch excitedly at the spot where rodents are detected.

 

5.5.4 Long-Term Population Suppression

Rodent populations have a remarkable capacity for growth and survival, but it is often people who provide the conditions under which that potential can be realized. Pest problems are a function of the design of industrial/agricultural production systems, ornamental landscapes and architecture, as well as human behaviors and beliefs that create, motivate, and maintain those designs. One must examine all circumstances that initially gave rise to a particular rodent problem and then make basic changes in the environment and human behaviors that resulted in food, water, and shelter for the pests. These measures include improved sanitation, housekeeping, and storage practices; altered landscape designs; and rodent-proofing of buildings. When the habitat is modified to reduce the basic factors needed for rodent survival, the control program has a much greater chance of lasting success.

 

5.5.5 Rodenticides for Structural Use

The use of toxicants has often been the primary treatment or intervention in many rodent control programs. Rodenticide applications have not proven ideal in all circumstances. They are contradicted in some situations (e.g., where children and pets are at risk and in food processing areas) and should be considered as only one of numerous potential interventions in an IPM program.

 

It is generally much safer and more effective to use chronic (multiple-dose) toxicants than acute (single-dose) poisons for rodents. There are times, however, when the quick-acting acute poisons are required, such as when the disease hazard is high or when a very large population must be reduced in a short period of time.

 

Acute (single-feeding) toxicants (Table 5.5.1) are very useful for achieving a quick knockdown of a rodent population. The same acute toxicant should not be used more than twice a year, preferably only once. When an acute toxicant is used repeatedly in the same locality, a bait shyness may develop. Hence it is best to periodically change the kinds of bait and active ingredient used.


Table 5.5.1. Acute rodenticides for structural rat and mouse control

Material/Example Product

EPA Reg. No.

Species/Situations

*Zinc phosphide

 

 

       ZP Rodent Bait Place Pacs

12455-59

Effective against Norway and roof rats, house mice

 

Note: Concentrations >2% are restricted-use

 

Bromethalin

 

 

       Tomcat Quickstrike Pelleted Bait

12455-97-3240

For Norway rats and house mice

Note: Some products are available only for indoor use in tamper-proof bait boxes. Read the label before purchase to be certain that these baits are applied correctly.

 

 

Probably 95 percent of all rodent-control operations in the United States use multiple-dose, anticoagulant baits (Table 5.5.1). The effects of anticoagulants are cumulative, and most baits must be consumed several times during a two-week period. That is why they are considered relatively safe for humans and other nontarget animals. Rodents rarely develop a shyness to anticoagulant baits of good quality. Anticoagulants act by interfering with blood clotting. The onset of symptoms is relatively slow, which allows time for administering vitamin K, an effective antidote, or giving whole-blood transfusions.

 

The past good safety record of anticoagulants is no reason for complacency. Recent reports indicate that more care should be exercised in their use because some of the products (brodifacoum, diphacinone, and bromadiolone) are acutely toxic to some rodents and nontarget species. Brodifacoum and diphacinone are particularly toxic to dogs and have relatively long biological half lives. These are important considerations from the standpoint of accidental primary or secondary poisoning of companion animals or wildlife.

 

For greatest effect, rodents should feed on the treated bait each day. The intervals between feedings should never exceed two days. Depending on the anticoagulant and the amount consumed, the first deaths in rats should occur about the fourth day post-exposure. Keep fresh bait exposed continuously for at least two weeks or until all feeding ceases. With some anticoagulants, shorter periods of exposure are recommended, so follow label instructions carefully.

 

5.5.5.1 Prebaiting

Prebaiting is the placement of nontoxic baits to create a high acceptance before the rodenticide is exposed. These baits should contain all the same ingredients (dyes and other additives) as the toxic bait, aside from the toxicant. After two to three nights of prebaiting, the rodents will overcome natural aversion to the new food items and will have learned to feed at these locations. The prebait should be handled with the same thoroughness and care anticipated for the actual poisoning. Prebaiting improves the effectiveness of acute rodenticides, but because anticoagulants are slow in taking effect, prebaiting is not needed. In using the more toxic chronic baits, prebaiting should make it possible to reduce exposure time and thereby reduce the probability of accidental intoxication of nontarget animals.

 

5.5.5.2 Bait Placement

It is best to place the bait where it will be in the rodents' normal line of travel. Baits should be placed under cover so the animals will feel secure when they feed. Put out more bait than you think necessary, unless prebaiting for three to five days has already indicated how much is needed.

 

Toss-type packets containing about 4 ounces (100 grams) of anticoagulant baits are commercially available from several sources. Rodents will readily gnaw into these bags to get at an acceptable bait. These bait packets have the advantage of easy placement beneath pallets, etc., where bait boxes are unsuitable because of their size.

 

5.5.5.3 Bait Boxes

Bait boxes, or other enclosed bait stations, should be large enough to accommodate several target rodents at one time. Each station should have at least two appropriate-sized openings. Bait boxes usually contain a feed hopper for holding the bait. Such boxes should be placed next to walls or in places where rodents will intercept them. Some bait boxes may be large enough that both water and dry baits can be placed inside. Bait boxes are available commercially in a variety of sizes and shapes. They may be constructed of water-resistant cardboard, wood, plastic, or metal. Locks, seals, and concealed latches are often used to make the boxes tamper-proof. All bait boxes and other permanent bait stations should be clearly labeled "Poison-Rodent Bait" or other appropriate wording.

 

When first put out, bait boxes should be checked daily. After a while it will be necessary to check the stations only once every other week to replenish or replace old bait with fresh. They must be visited often enough so that ample fresh anticoagulant bait is available.

5.5.5.4 Paraffin Bait Blocks

Paraffin blocks for rat and mouse control are available through pest control suppliers. Some firms offer bait blocks in several flavors, or containing different bait ingredients, that are advertised as more appealing to certain populations of rodents. Again, these bait blocks reportedly give good control, particularly where food is limited. Bait blocks have been found particularly valuable in control of roof rats where the blocks can be fastened to telephone poles, fences, or the rafters of buildings. Dogs will occasionally chew on a block as if on a bone, which creates a hazard. Therefore, bait blocks should be placed out of the reach of dogs and other curious domestic animals. Because loose cereal or pellet baits are invariably accepted more readily than are paraffin blocks by Norway and roof rats, blocks should be used only in situations where other baits are unsuitable.

 

5.5.5.5 Traps

Trapping can be an effective method of controlling rodents but requires somewhat more skill and labor than baiting. Traps alone are sometimes not completely effective for removal purposes, but can be very useful in conjunction with habitat modification. Trapping is recommended where use of poisons seems inadvisable and is the preferred method in homes, garages, and other structures where there are few rodents, and nontarget species risks may be great. Trapping has several advantages: (1) It does not rely on inherently hazardous rodenticides, (2) it permits the user to view his or her success, and (3) it eliminates rodent deaths in inaccessible locations, which frequently creates odor problems when poisoning is done within structures.

 

 

Table 5.5.2. Chronic rodenticides for structural rat and mouse control

Material/Example Product(s)

EPA Reg. No.

Formulations

Chlorophacinone

 

 

     J.T. Eaton AC Formula 90

56-70

Bait blocks, pellets

     Rozol Pellets

7173-151

(other formulations)

*Diphacinone

 

 

Note: all concentrations >3% are restricted-use

 

 

Bromadiolone

 

 

     Maki Paraffinized Pellets

7173-187

Pellets

     Maki Rat & Mouse Bait Packs

7173-188

 

 Note: Good control in Warfarin-resistant rats, toxic to poultry

 

*Warfarin

 

 

     707 Kill Rats-Kills Mice

2393-166

Ready-to-use baits

Note: concentrations. >3% are restricted-use

 

(other formulations)

Cholecalciferol (Vitamin D3)

 

 

    Rampage Rat and Mouse Bait Place Pac

3240-42

Bait

*restricted-use pesticide; may be purchased and used only by certified applica