FOR-43 MANAGING RABBIT AND VOLE PROBLEMS IN KENTUCKY = ORCHARDS

From: Subject: FOR-43 MANAGING RABBIT AND VOLE PROBLEMS IN KENTUCKY ORCHARDS Date: Thu, 3 Jun 2010 14:22:14 -0400 MIME-Version: 1.0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Content-Location: http://www.ca.uky.edu/agc/pubs/for/for43/for43.htm X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5931 FOR-43 MANAGING RABBIT AND VOLE PROBLEMS IN KENTUCKY = ORCHARDS FOR-43
MANAGING RABBIT AND VOLE PROBLEMS IN = KENTUCKY=20 ORCHARDS
ISSUED: 5-90
REVISED:
Thomas G. Barnes, Extension = Wildlife=20 Specialist=20

Voles (Microtus spp.) = and=20 cottontail rabbits (Sylvilagus floridanus) may cause extensive = damage to=20 orchards by girdling seedling and mature trees. The amount and extent of = damage=20 will vary, and the best approach is a pest management system that = integrates=20 biological, mechanical, and chemical prevention and control techniques.=20

Animal Facts and Biology
Voles.
Often referred to as meadow or field mice, voles are = small=20 compact mammals with stocky bodies, small rounded ears, short legs, and = a short=20 tail. When fully grown, voles are 4 to 5 inches long. Their long, coarse = hair=20 can be blackish, grizzled, or reddish.
The three vole species that damage Kentucky orchard = trees are=20 pine voles (Microtus pinetorum), prairie voles (Microtus=20 ochrogaster), and meadow voles (Microtus pennsylvanicus).=20 Identification of individual species is essential because pine vole = damage=20 occurs below ground.
Voles = eat a variety=20 of grasses and broad-leaved weeds. They will also eat seeds, tubers, = bulbs, and=20 rhizomes. Prairie and meadow voles feed on tree bark primarily during = the fail=20 and winter. However, pine voles characteristically attack trees of all = sizes=20 during all seasons. Most pine vole damage occurs below ground where the = animals=20 feed on rootlets and the bark of larger roots.
Voles do not hibernate and are active all year long. = They are=20 most active during the day. Areas of activity are small (1/4 acre) and = depend on=20 population number, food supply, habitat, and season. A typical vole = habitat=20 consists of heavy, dense ground cover where the animals construct many = burrows,=20 tunnels, and runways. A single burrow system may contain several adults = and=20 young.
Voles breed from = January through=20 October in Kentucky and can produce an entirely new generation within = about 60=20 days. Vole numbers fluctuate from year to year; under favorable = conditions,=20 populations can increase rapidly. Most orchard problems occur during = these=20 periods of rapid population growth.
Although voles have a high reproductive rate, they = are also a=20 mainstay in the diet of hawks, owls, foxes, coyotes, and other = meat-eating=20 animals. In addition, the lifespan of a vole is short, ranging from 2 to = 16=20 months. More than 80% of young voles die in their first month of life.=20

Rabbits.
Our most = abundant and common=20 rabbit is the eastern cottontail. The cottontail rabbit is often grouped = with=20 the rodents (mice, squirrels, rats) because of its large, prominent = front teeth.=20 However, rabbits have a second, smaller set of teeth directly behind the = first=20 set, a characteristic which places them in the group Lagomorphs. =
Typical eastern cottontail rabbits weigh = between 2=20 and 4 pounds and are 15 to 19 inches long. Cottontails appear gray to = brownish=20 gray with a short tail and big ears. The underside of the tail is white = and=20 looks like a cotton ball. Hence the name cottontail.
Rabbits will devour a wide variety of green = vegetation. A=20 rabbit's appetite varies considerably with season and locality. During = the=20 winter, rabbits appear to prefer the bark of apple trees, black and red=20 raspberries, and blackberries. Clovers, grass, and broad-leaved weeds = are a=20 mainstay in summer diets. Cottontails usually prefer to feed at night = although=20 they are also active during daylight hours.
Rabbits tend to concentrate in favorable habitats = around a=20 brushy fencerow, brush or junk piles, upland thickets, or field edges. = Their=20 travels usually do not exceed 10 acres. Population levels are directly = linked to=20 the quantity and quality of habitat present.
The lifespan of a cottontail is short (12 to 15 = months);=20 however, cottontails have an extremely high reproductive potential. = Kentucky=20 cottontails may have 3 to 8 young per litter and up to 4 litters per = year. The=20 first litter usually appears in March.
Fortunately, this high reproductive potential is not = reached=20 because cottontails also have a high death rate. Cottontails, like = voles, are a=20 mainstay in the diets of most meat-eating animals.
Predation, disease, weather, and encounters with = humans=20 contribute to the annual death rate. Up to 35% of the young die within = the first=20 month, and 65% of the remaining animals will die over winter.=20

Damage Identification
Most damage to=20 orchard trees occurs during the winter when other preferred food = supplies have=20 dwindled and the animals resort to gnawing on tree bark. Because of the=20 cottontail's high reproductive rate, control is sometimes necessary to = reduce=20 damage. However, complete eradication or extermination is not possible,=20 necessary, or even desirable because of the cottontail's status as a = preferred=20 game species. Before attempting to prevent or control damage occurring = to=20 orchard trees, be sure to correctly identify the culprits responsible = because=20 control techniques vary by species. Correct identification is relatively = easy=20 based upon evidence at the site of damage.
Girdling and gnaw marks do not necessarily indicate = vole=20 damage because cottontail damage can look similar. However, the presence = of=20 tracks, droppings, and burrow systems should verify initial = observations.=20 Typical vole damage can be differentiated from rabbit damage by the lack = of=20 uniformity of gnawing marks and the area of tree damage. Gnawing marks = from=20 voles usually occur at or below the surface at various angles and in = irregular=20 patches. The gnawed patches are approximately 1/8 inch wide, 3/8 inch = long, and=20 1/16 inch deep.
Rabbits, on = the other=20 hand, clip tender young shoots and terminal buds as well as gnawing on = the=20 trunk. The gnawing marks are larger and appear as clean, knife-like cuts = at a=20 45-degree angle. Rabbit tracks and round droppings are also quite = distinctive.=20

Prevention and Control
An = orchard=20 owner should pursue four general steps when developing a successful = integrated=20 pest management system. These include:
1.Correctly identifying the animal species causing the = problem.=20
2.Modifying the habitat to = make it less=20 attractive to the problem animals.
3.Using environmentally sound prevention and control = techniques=20 appropriate for each individual situation.
4.Monitoring and evaluating the area for signs of = reinfestation=20 to determine if the control worked or if additional control is = necessary.=20

The best approach to managing = vole and=20 rabbit damage in orchards is to use an integrated system with a variety = of=20 techniques. Not all techniques work in every situation, and orchard = owners must=20 be willing to use different approaches for their individual problem. = Often a=20 combination of techniques produces the best results. Control works best = during=20 the winter, reducing next year's breeding population. Habitat = modification and=20 exclusion provide the best long-term control for both voles and = cottontails.=20
The various prevention and = control=20 techniques may be grouped as (1) biological, (2)mechanical, or (3) = chemical.=20 Each technique has advantages and disadvantages depending on management=20 objectives, expense, location, and situation. The options for preventing = and=20 controlling voles and cottontails in orchards are discussed below.=20

Biological Control.
The = three types=20 of biological control are habitat modification, population reduction = through=20 hunting or trapping, and installation of raptor perches.
Habitat modification is particularly effective in = deterring=20 voles and rabbits. Dense, heavy vegetative cover, mulch, and weeds = provide=20 optimum habitat for voles and rabbits by providing food and protection = from=20 predators. If you remove this food and cover source, the area will = provide less=20 suitable habitat. If mulch is used in the orchard, it should be placed = no closer=20 than 3 feet to the trees. Vegetation remaining between rows should be = mowed=20 regularly.
Soil tillage is = particularly=20 effective because it eliminates any cover, destroys existing burrow = systems, and=20 kills a percentage of the vole population. Brush piles, weed patches, = junk=20 dumps, and stone piles in or adjacent to the orchard should be removed, = thereby=20 eliminating places where rabbits live and hide. This method of control = is one of=20 the most effective, long-term solutions in reducing vole and rabbit = damage to=20 orchard trees. It has several advantages over other techniques because = it is=20 economical, does not place harmful chemicals into the environment, and = is a=20 long-term solution to the problem, not a quick fix.
Hunting rabbits in rural areas is a quick, easy, and = effective=20 method of control. Cottontails, avidly pursued by hunters, are legal = game=20 animals in the Commonwealth of Kentucky. A permit must be obtained from = your=20 county conservation officer to destroy cottontails anytime except during = the=20 legal hunting season. During hunting season you must have a valid = Kentucky=20 hunting license to shoot cottontails.
You must be persistent if hunting is your sole = method of=20 control. Removing rabbits in one year does not guarantee rabbit = populations will=20 remain low because of the rabbit's high reproductive potential. The best = results=20 can be achieved by hunting in the early morning or evening when the = rabbits are=20 most active. By permitting hunting, orchard owners provide public access = to a=20 public resource while reducing damage problems.
Trapping is not effective in reducing large vole or = rabbit=20 populations because time and labor costs are prohibitive. However, small = populations can be controlled by trapping. Live trapping is the most = effective=20 way to remove cottontail rabbits. There are a variety of commercial live = traps=20 available at hardware, agricultural supply and feed stores, or sporting = goods=20 stores. Live traps are more effective if you cover them with canvas or = some=20 other dark material.
Rabbit = traps can be=20 baited with cob corn, oats, or dried apples during the fall and winter. = Placing=20 rabbit droppings inside the trap may make it more effective. Place the = traps in=20 areas where cottontails have been feeding or resting close to suitable = cover.=20 Bait the trap and wire the door open for several days. Once the bait is = being=20 taken regularly, remove the wire and set the trap. You must check the = traps=20 daily and remove captured animals. If the trap fails to catch any = cottontails=20 within a week, move the trap to a different location.
When vole populations are low or concentrated, = trapping may be=20 an effective control technique. The simple, wooden snap trap or Sherman = live=20 trap is commonly used. Bait the traps with a mixture of peanut butter = and=20 oatmeal or dried apples. Trap placement is crucial as voles rarely stray = from=20 their usual travel routes. Examine the area for nests, burrows, and = runways in=20 the grass or mulch. Place the traps perpendicular to the runway with the = trigger=20 end in the runway. Be sure to set enough traps (remember a vole's = territory is=20 about 1/4 acre). Fifty to 100 traps should be sufficient in many small = orchards.=20 Traps must be checked daily and dead animals removed.
One final biological method of reducing vole and = rabbit=20 populations is to install raptor perches. These structures provide = hawks, owls,=20 and other birds of prey an elevated "overlook" where they stand waiting = to catch=20 small animals. One perch per acre or two, located on higher ground, = should be=20 sufficient. While predators alone do not control vole or rabbit numbers, = installation of raptor perches may help keep populations low once they = have been=20 reduced through alternative techniques.=20

Mechanical Control.
The = most=20 effective mechanical control methods are those which prevent animals = from=20 entering the general area (fencing) or preventing individual trees from = being=20 clipped. While fencing is the best way to eliminate animal damage, the = cost of=20 constructing effective fences is often prohibitive. Examine costs and = benefits=20 carefully before investing in this option. Even though fences may seem = costly,=20 with proper care they provide relief and protection from damage for many = years.=20
Rabbit- and vole-proof = fences are easily=20 constructed of 1-inch mesh netting woven or poultry wire. The fence = should stand=20 30 to 36 inches high. The bottom 6 inches should be turned outward and = buried at=20 least 6 inches under the surface. The lower 2 feet of the fence should = be=20 covered with a small (1/4 inch) mesh wire or hardware cloth to prohibit = voles=20 from entering. Be sure to keep 6 inches of this below ground to prevent = voles=20 from burrowing under it. Inexpensive chicken wire fences can also be = constructed=20 to exclude rabbits; however, this fencing will require periodic = replacement.=20
In most situations, = protecting=20 individual trees is more practical than excluding animals from the = entire=20 orchard. Plastic or 1/4 inch hardware cloth cylinders, 18-24 inches high = and 4=20 inches under the surface, can be placed around individual trees. For = adequate=20 protection, these cylinders should be braced away from the trunk to = prevent=20 cottontails from pressing them against the tree and gnawing through = them. There=20 are a variety of commercial plastic, metal, or nylon tree guard tubes = and=20 wrappings available. Contact your local garden center or agricultural = supply=20 store for materials available in your area.=20

Chemical Control.
The two = main groups=20 of chemicals used to prevent or control rabbit and voles are repellents = and=20 toxicants. Repellents work well in reducing cottontail damage, however, = their=20 effectiveness in reducing vole damage has not been demonstrated. There = are no=20 toxicants (poisons) registered for use against rabbits, however, = toxicants have=20 been a mainstay in controlling vole damage.
Chemical repellents are classified as either contact = or area.=20 Contact repellents are applied directly to plants and repel by = unpleasant taste,=20 whereas area repellents are applied next to plants and repel by smell = alone.=20 Area repellents may be slightly less effective than contact repellents. = It is=20 important to recognize that repellents will not eliminate damage. They = only=20 reduce the severity of browsing.
Repellents should be applied before damage occurs = and must be=20 reapplied frequently after a rain, heavy dew, or new plant growth. = Always follow=20 label directions for the repellent you are using. Never apply repellents = to any=20 portion of a plant likely to be eaten by humans unless the label permits = it.=20
There are a variety of = commercially=20 available chemical repellents on the market today. During the dormant = season=20 apply contact repellents when temperatures are above freezing.If you = have rabbit=20 problems during the growing season apply a contact repellent at about = half the=20 recommended concentration. Commercially available repellents can be = found under=20 a variety of trade names, and the active ingredient is usually bone tar = oil,=20 thiram, fermented egg solids, or ammonium soaps of fatty acids. =
Be imaginative in your approach to using = repellents.=20 For example, placing several handfuls of human hair in a mesh bag and = allowing=20 it to blow in the breeze may be effective. Some people have successfully = used=20 hot pepper sauce to make trees distasteful to animals. You can make your = own hot=20 sauce repellent by mixing 1 tablespoon hot sauce in 1 gallon water. Add = 2=20 tablespoons antidesiccant per gallon to allow the repellent to stick to = the=20 bark. Spray the foliage and bark when temperatures are above 40 degrees = F.=20
A variety of toxicants is = registered for=20 use in controlling vole populations. When using toxicants, take extra=20 precautions to ensure the safety of children, pets, and nontarget = animals.=20 Follow product label instructions carefully. Never use a pesticide in a = manner=20 inconsistent with its labeling. Failure to comply with directions = provided may=20 subject you to severe sanctions and penalties provided by state and/or = federal=20 laws.
Toxicants designed to = kill voles=20 and mice are called rodenticides. Rodenticides are classified as = single-dose or=20 multiple-dose depending on how long it takes the poison to act. =
Single-dose (acute) rodenticides require = only one=20 feeding to be lethal. Multiple-dose (anticoagulant) rodenticides are = slow acting=20 because voles poisoned with anticoagulants die from internal bleeding. = Thus,=20 they must be consumed for several consecutive days to be effective. They = are=20 probably the safest and most preferred type of rodenticide.
Many types and brands of anticoagulant = rodenticides=20 are available on the market today. The most effective and potent contain = cholecalciferol, brodifacoum, bromadiolone, chlorophacinone, and = coumafuryl.=20
Because voles must feed on = the bait for=20 3 to 5 days, the bait must be available for an extended period of time. = Be sure=20 to place the bait in runways or next to burrows so voles will find it = during=20 their normal travels.
One = method of=20 keeping bait available in good condition is to establish bait stations. = You can=20 purchase commercial bait stations or make your own from 2- to 3-inch = diameter=20 plastic pipe.
Many growers = place=20 shingles or boards in their orchards during September. They visit these = stations=20 during October and inspect them for vole runways beneath the covers. If = runways=20 are found, a rodenticide is placed under the boards. Some growers use = machines=20 which build artificial trails and dispense rodenticide in these trails.=20
Zinc phosphide is the most = commonly used=20 acute poison. It is a restricted use pesticide. Any person using this = pesticide=20 must be certified by EPA or work directly under the supervision of a = certified=20 person. Place the bait in runways or next to burrows where voles will = find it.=20 To increase the effectiveness of poison grain baits, prebait with good = quality=20 grain for 3 to 5 days. The best time to use grain baits is during the = winter.=20
One problem with using zinc = phosphide is=20 "bait avoidance or shyness" which occurs when voles eat only enough to = make them=20 sick. If this happens, voles will not eat any bait for 6 months or more. = To=20 avoid this situation, do not use zinc phosphide more often than every 6 = months=20 and always follow label instructions. This rodenticide also comes as a = tracking=20 powder or in paraffin blocks.
Trade=20 names are used for simplicity. No endorsement is intended, nor is = criticism=20 implied of similar products not named.