ECSONG: A Nut Growers' Manual - General

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ECSONG: A Nut Growers' Manual - General

Many arboricultural, horticultural and silvicultural practices are common to all the nut bearing trees and shrubs. These are covered together here in order to avoid repetition in every species section.

Globally, nut trees have a tremendous potential to arrest soil erosion, provide a nutritious source of carbohydrates, fats and protein and offer a dual-cropping opportunity on poor as well as good agricultural land.

Nut bearing trees and shrubs are deciduous hardwoods except a few coniferous species in the genus Pinus and the family Gingkoaceae. The common "hardwoods" nuts include the genera Juglans, Carya, Castanea, Fagus, Quercus and Corylus. These are called dicotyledonous plants and possess massive, meaty cotyledons which we prize as "nut meats" or "kernels." The pericarp (see illustration) is usually woody and hard as in Juglans, Carya and Fagus. Castanea and Quercus have thinner pericarps. Hardwood nuts are termed hypogeal except beech, as they remain in the soil after germination. The cotyledon feeds the juvenile plant until it produces primary leaves.

Coniferous species are slightly different (see illustration). They possess a meaty megagametophyte or food storage area. The seed is raised above the ground after germination epigeous. Fagus (beech) is epigeous.

It is important that nuts are planted horizontally so that the radicle and plumule grow in the most advantageous position (see illustration).

Nut trees prefer a temperate climate and fertile soil. Generally, the climate should provide one hundred and fifty frost free days, with lowest temperatures above minus thirty degrees Celsius. Note that late spring frosts (June) and early fall frosts (September) can cause severe damage. North facing, gentle slopes are ideal. Lower slopes with frost pocket potential should be avoided. As for the soils, they should be deep, well-drained sandy or clay loams. A minimum depth of one meter is essential. Heavy weed and grass competition should be eliminated for proper soil exploitation by the tree roots.

Trees should be spread apart sufficiently to allow full crown development. Spacings of ten to twenty meters between trees is usual. If timber is the objective, grow in mixture with other species at closer spacing.

Climatic Zones

Nut trees are temperate zone species. In Ontario, they grow naturally in Zone 6, or warmer from Kingston to Goderich. The Great Lakes influence is a controlling factor. One hundred and fifty frost-free days are essential. In general, where peaches grow, so will nuts, but other fruit tree areas may also suffice. Acceptable microclimates may be created by coniferous windbreaks on the north/west sides. These moderate the climate at distances up to ten times their height.

Site Selection (9)

Agricultural site Classes 1 to 4 are preferred. A deep, well-drained loamy soil is best. A deep hardwood forest soil will also support nut trees for timber purposes. Consult local soil maps, Ontario Ministry of Natural Resource (OMNR), Ontario Ministry of Agriculture and Food (OMAF) and Canada Agriculture.

A gentle north-facing slope free of frost pockets is desirable. A south facing slope will encourage early bud break, winter damage, frost heaving, and early and late frost damage.

Each species has its own spacing and mixture prescription. It is unlikely that nut plantations of the magnitude of large fruit orchards will be established in the near future in this region because of the climate. Unlike soft fruits, you cannot be so certain of your crop. Nut culture is still in its infancy and much is to be learned. Besides, governments have not invested in intensive research projects. The avid amateur is carrying the ball. With this in mind, and a number of "proven" cultivars in hand, get on with it.

Most nut trees require spacing of up to forty feet, tying up a lot of land. Why not consider dual cropping (15) the site? For example, you could try soybeans, forage crops, wheat or cash crops. The land must be kept free of weeds anyway, so the Class 1 to 4 agricultural land could be made to yield something else as well as the long-term tree crop.

Site Preparation (9)(1)

The site must be free of other vegetative competition. The most intensively prepared sites require less post-plant tending.

Mechanical methods of site preparation, including ploughing and discing with conventional farm equipment, should be done the year prior to planting. Frequent discing and harrowing will minimize weed establishment.

Chemical methods of site preparation require a complete spray of the site with a non-selective herbicides. Roundup, often considered environmentally safe, can be used. It need only be applied once to fully prepare a tree site. In using herbicides, note that each species has its own herbicide tolerance.

Strip preparation will minimize soil erosion and is less costly. Strips at least two meters wide at five meter to fifteen meter spacing, depending on species prescription should be done the summer prior to planting. After the vegetative kill, plough and disc. Some prefer to plant directly into the dead vegetation which acts as a mulch and is less costly. In any case, a postplant application of Simazine 80W is required to minimize new weed seed germination (6)(8)(1)(5)(9). Simazine may leach in sandy soils and damage the roots of some species. Lower rates should be used on sandy soils.

For example, in all the Juglans species, normal rates would be:

  • After planting...................5.6 kilograms active ingredient per hectare.
  • First fall or spring..........6.7 kilograms active ingredient per hectare.
  • Second fall or spring......6.7 kilograms active ingredient per hectare.

Band spraying, a technique in which the chemical is sprayed along a strip of ground, is recommended as the minimum site preparation treatment. Individual spots reduce the growing area and may result in over or under application. Mow vegetation between rows short twice a year to discourage mice and voles.

Obtaining Stock (1) (2) (7) (8)

Obtaining suitable seed and stock for planting is the single most important step toward ensuring success in nut growing. This material, including seed, seedlings and clones, may be gotten from a variety of sources, and must be handled carefully pending planting.

(i) Source Stand Selection

Nut trees rarely grow in pure stands in Eastern Ontario. Native butternuts, beech, oak and hickory are frequently found in mixtures of upland hardwoods. Sources include seed collection areas recognized by the Ontario Ministry of Natural Resource (OMNR), the SONG Ottawa Chapter's "Inventree" file, recommendations from interested naturalists (Ottawa Field Naturalists) or personal knowledge.

The Chapter's "Inventree" file is a collection of cards each recording a site in eastern Ontario or western Quebec where the wild or feral nut trees found growing could provide planting stock. The file now records some seventy or so sites.

In any event, the chosen trees must possess the desired qualities: for timber production look for tall, straight, dominants and co-dominants, fine branching, strong crowns, clear trunks; for nut production look for full crown, generally healthy, large, well-formed nuts, disease-free, easily cracked, large cotyledons (nut meats), etc.

Plantations have been established over the years on a variety of sites around eastern Ontario. The seed sources were usually "southern", either from Ontario, the U.S. or Europe. Ontario Ministry of Natural Resource (OMNR) produced walnut seedlings from southern Ontario seed sources and these eventually found their way over large areas of the province. They are in woodlots, in small plantations or as individual shade trees. These are of interest, as the survivors demonstrate local hardiness and adaptability to local site conditions.

A few specialist nursery trees (imported from the U.S. or Europe) were planted as semi-ornamental groves and laneway strips in rural area. These also may prove valuable, especially those established away from the "urban climatic dome". The Dominion Arboretum at the Central Experimental Farm in Ottawa has a variety of nut species.

(ii) Individual Source Tree Selection.

Nut trees appear as individuals all over Eastern Ontario. Most of these have been planted as ornamental in urban areas. Again, Ontario Ministry of Natural Resource (OMNR) and specialist nurseries supplied some of the stock, but a few avid "nutters" have imported their own from all over the U.S.A. and sometimes from Europe and Asia.

These individual trees have demonstrated various degrees of success, depending on site, microclimate and cultural practices. Nearly every town and village has its exceptional nut trees.

Ottawa has excellent examples of individual trees in its Dominion Arboretum. Unfortunately, these do not always demonstrate adaptability to Eastern Ontario conditions as a whole. The "urban climatic dome" is an artificial microclimate created by buildings, masonry, other trees, etc. Heat radiation and a certain amount of local "smog" from the total urban environment increases the growing zone from a Zone 4 to a Zone 6 - ideal for nut and fruit trees. Besides this, urban areas possess pockets of good soil conditions and drainage, and above all, the local people usually tend these trees carefully.

Nevertheless these trees constitute our working gene pools. The origin of these trees is not known in most cases so all we have to go on is their present performance.

They may produce exceptional nut crops, but, again what do we want? Timber or nuts for consumption? Each tree must be assessed for desired qualities. The nuts must be carefully examined, not just one or two from a tree, but a large number to get a pattern. If they are large, crack well and have good nut meat - full, good colour and flavour, you have a good tree. Mark it well and discuss with the owner the possibility of using it as a "Crop Tree" for collecting seed and scions. This applies to any good tree whether in a stand, in a woodlot or individuals in a town.

Keep in mind that seed will not necessarily produce a tree with the exact qualities observed. However, the taking of scions and grafting same onto hardy root stocks will.

Propagation of Stock

Stock may be propagated a number of ways, namely as seed, seedlings, by vegetative methods such as grafting or layering.

(i) Seed Crop Assessment (7)

As previously mentioned, suitable trees must be found, tagged, classified, measured, mapped and recorded - then you wait for a good "seed year." Some trees and species produce a few seeds every year then a good "seed year" every two to five years. Seed collected during seed years is usually superior to scattered, annual seed. Under intensive orcharding practices, trees produce acceptable crops annually. Assess the potential in the early summer for fall collecting.

(ii) Judging Seed Quality

Check for aborted nuts, insect damage, seed fullness (nut meat) and crack a good sample of the nuts to determine if they are satisfactory. Float them in water. Those that sink are generally okay, whereas the floaters are invariably empty.

(iii) Seed Ripeness

The seed is ripe about September and October. It falls from the tree or can be shaken off. Watch the squirrels. They are active just before the seed is entirely ripe (at which time it drops). You can collect from their cache, if you can find it, but the seed will represent the stand of trees, not the individual. An individual tree growing alone is probably self-pollinating, consequently the fruit may not be fully developed. Most nut trees have both pistillate and staminate flowers on the same tree (monoecious). (10)

(iv) Seed Collecting Methods (7)(11)

Equipment required includes: ladders, tarpaulins, burlap bags, linen tags (or other durable material, to record tree data, picking date, etc.), long bamboo poles, and record sheets.

If scions are to be collected: long ladders, pole pruners, hand pruners, plastic storage bags. The scions should be about one foot long and taken from the upper crown from last year's growth. Collect during the dormant season in February or March. Avoid scions with large pith to wood ratio.

(v) Seed Storage (8) (1) (11)

Nuts should be stored using different methods for each species. In general, walnuts are de-husked immediately and dried. Others require cleaning and drying and storage in a cool, dry and well-ventilated place. When the nut kernels snap cleanly when broken with the fingers, they are ready for storage below seventy degrees Fahrenheit (twenty degrees Celsius). They become rancid if stored at warmer temperatures for a long period of time. Loss of moisture below sixty percent reduces the survival chances of the embryo. Seed for planting should be stored in sealed containers in a cool place.

(vi) Seed Dormancy (1) (11)

Most embryos remain dormant after the seed ripens until this physiological state is broken. The physiological reason for dormancy is to protect the embryo over the harsh winter period until more favourable conditions in the spring. White oak is an exception as it germinates immediately after ripening. In any event, seeds may be planted out immediately in the fall to fulfill their after-ripening requirement naturally in the ground. Some seeds with hard shells (seed coats) may require fracturing, or weakening of the coat (by mechanical or chemical abrasion for example) to allow the entry of water to activate the embryo and allow it to burst out.

(vii) Stratification of Seed

Exposure to moist, cool temperature naturally in the ground or artificially in a refrigerator is called stratification. About fifteen hundred hours at three degrees Celsius is the stratification requirement for native species. (12). If the seed cannot be planted out in a nursery bed in the fall, it should be stratified, either in the ground or in the refrigerator.

In the ground, place hulled nuts one layer deep between layers of sand, peat or sawdust in a box protected by wire to keep out vermin. Bore holes in the top or bottom of the box to let out water. Sink the box into well-drained ground to the top and cover with a mulch of straw or sawdust. There the temperature will be about thirty five to thirty eight degrees Fahrenheit (three to four degrees Celsius) and humidity seventy percent or more. Alternatively, small quantities of nuts may be stored in the refrigerator in moist peat in a sealed container for the required time, in artificial stratification.

In the spring remove the nuts and plant in rows in the nursery bed. There, some percentage will germinate in the first year, some in the second, some even in the third, fourth or fifth years.

(viii) Special Treatment of Seed

White oak must be planted in the seedbed in the fall. Red oak must be stratified as with other nut species. All nuts in the stratification box or in the seed bed must be covered with wire mesh to exclude vermin. Rodents and birds eat the tender emerging growing points. A wire enclosure at least two feet high and buried six inches into the soil is the best. Poison baits (be very careful!) and repellants may be also useful.

(ix) Propagation by Layering Stock

Another method of propagating certain nut species is layering. (1) (8) This method produces a cloning situation whereby all progeny are similar. Filbert, as called hazel, is the one nut tree lending itself to this system because of its multiple stem, shrub-like habit. Branches may be bent down, pegged into the soil in the spring and may root in one to two years. Both American and European varieties and their hybrids may be propagated this way. The severed, rooted branch can be transplanted into a nursery to develop into a stronger plant. Suckers originating at the root collar area can be isolated with their own root system, dug up and planted.

Root layering has been successful with Black Walnut (19) and it may have possibilities with other similar species.

(ix) Propagation by Grafting Stock

Superior trees can also be developed by grafting (1) (8) (12). Grafting and budding are the most reliable methods of propagating a nut tree true to its genetic qualities. Both of these are done in the spring when the cambium is receptive (i.e., the bark is easily removed from the wood).

Ring or patch budding techniques may be employed using a single bud. A scion is taken in February or March and placed in water in a cool place (seventy degrees Fahrenheit, twenty degrees Celsius). The bud is carefully removed when the bark begins to loosen. Do this when the stock plant is in a similar condition. Tie securely and seal with grafting wax to prevent drying. When the bud is set cut the binding on the opposite side to the bud. Remove all other buds on the stock. Support the new shoot by tying it to a support stick or the upper part of the stock.

Grafting of a complete scion to a suitable stock involves standard grafting practices. Cleft, side, splice, or inlay grafts may be employed. As with bud grafts, the scions are collected in February or March and stored in a cool damp medium until needed.

Problems such as sap build-up in the graft necessitate drainage methods such as leaving the binding off the base of the graft. Walnut and hickory both bleed sap.

Consider the care of grafts. After the scions are set and waxed, cover the grafted stubs with white ventilated paper bags: five pound size bags with the corners cut out will do. All buds on the stock itself should be rubbed off to give all the energy to the scion. Inspect every week and remove any competing stock growth. Support the new scion growth with splint stick tied securely to the stock and scion.

Late May through June in Eastern Ontario, after the root stock has started to grow, is the best time to graft. Take scions from the most vigorous shoots with a small pith to wood ratio. Reduce the storage time of scions by taking them when the root stock is ready. This applies to local collections areas. If you collect at a distant site, do so at the latest possible date and keep scions cool and moist in peat or sawdust in a root cellar or cooler. Seal the cut end with grafting wax.

Black walnut root stock is used for most Juglans species grafting. Bench grafting indoors on two to three year old potted stocks requires greenhouse facilities. Outdoor grafting on established seedlings is commonly practiced in their permanent location.

Planting Tree Stock (1) (8)

Plant only trees with a good root system, and a well-formed top. Roots should be trimmed for even length and to remove damaged ends, especially in the case of tap roots.

(i) Digging and Holding the Seedlings.

If removing trees from your own beds, lift with a fork if possible. Dig as deeply as possible to capture the tap root. Do not hope to transplant trees older than one or two years, without difficulty, because the tap roots will be excessively long.

Place the dug trees on damp burlap and make a roll as you add trees to it. Make the roll as large as you can carry to the field. Unroll only as you plant the trees.

If you cannot plant immediately, place the rolls in a cool root cellar or shed for up to two days. If trees have been received from a commercial nursery and cannot be planted immediately, keep them in their original container in a cool place, but only for a few days.

If trees are to be kept over two days, heel into a protected holding bed. The Ontario Ministry of Natural Resource (OMNR) publication, "Care and Planting of Nursery Stock", explains the procedure.

(ii) Planting Method for Seedlings

Plant as determined by your plantation plan, which should note that each species has its own requirements and spacing. Hand planting is the most reliable method. This is an orchard type planting and rules applying to orchards work here, namely:

  • Select only sound seedlings.
  • Prevent the roots from drying out.
  • Dig a hole deeper than the root and work about one half kilogram of bone meal into the top soil.
  • Replace the soil carefully and work it around the well spread out roots with a tamping stick. Avoid heavy foot packing. Keep the tree vertical and plant it with the root collar at ground level or one inch below.
  • Water the tree to settle the soil and maintain root zone moisture.
  • Mulch with sawdust, wood chips or straw.
  • If the trees are large enough, apply a rodent collar to each and bury it down to the root zone.
  • Control weeds by manual or chemical methods.(1) (8) (3) (9)

Planting by Direct Seeding

Direct planting of seeds has the advantage of eliminating transplant shock common to seedlings. Seeds are easy to plant, so the method is cost effective. The main problem will be protecting them from rodents.

(i) General Handling of Seed.

Seed must be viable in order to grow. Good seed years produce better seed than intermediate lean years. De-husk all seed and select large, sound, well-formed nuts. Test by placing in a tub of water, remembering that floaters are sterile, whereas sinkers may be okay. This is only a guide. Try a cutting test to be sure, opening seed to assess kernel quality. Insect damage indicates defective seed.

(ii) Seeding in a Nursery Bed.

If you wish to grow seedlings, set up a small nursery bed. The area should be protected from drying winds, well-drained and of light soil.

The better time to plant the nursery is in the fall. Space seeds about six inches apart in rows about twelve inches apart. Plant to a depth of one half to three inches. Lay seeds on their sides in the ground, not vertically. Firm the soil and mulch the bed with sawdust, straw, wood chips, etc.

In the nursery bed, planting in the fall is the better than planting in the spring. However, if spring nursery planting is desired, use stratified seed only. Then proceed as with fall seeding, including mulching.

On germination, remove mulch from the new growing points only, leaving the ungerminated seeds covered. Keep the mulch on the bed for protection from high summer heat. Irrigate beds as required. Apply a fertilizer, such as 20-20-20, once during the growing season to maintain growth and colour. Do not apply after July 15th. Weeds must be controlled by hand cultivation or chemically. (1) (5)

(iii) Direct Seeding into the Final Site

There is a very good reason to plant seed directly into the final site. Deep tap-rooted species such as the hickories suffer from transplant shock. In fact, most nut species produce a long tap root the first year with little top growth. It is tempting to wait to transplant seedlings until you can see good top growth. However, by this time the tap root is deep into the soil and very difficult to extract intact. The risk of transplant shock and the resulting loss of the plant is high.

Direct seeding into a previously prepared permanent site is desirable. Plant two or three selected seeds about two to three inches deep, on their sides. Then mulch and cover with wire mesh and hope the rodents stay away. After germination, select the best seedling and cull the others.

(iv) Protection for Nursery Beds and in the Field

In the nursery bed, enclose the entire area with wire mesh about two feet high and dug into the perimeter at least six inches deep to discourage birds and digging rodents. Alternately, a fine wire mesh simply placed five centimeters (about two inches) high above the bed seems to block the vermin.(vi)

In the open field, if the ground is completely cultivated around the seed spots and the whole site is free of grass and weeds, rodents rarely venture into such an exposed area. Birds will consume new growing points. Leave a natural tree or two around the field to act as a hawk or owl perch. You may even set up a few high poles with cross arms to attract these predatory birds.

Tending the Plantation (1) (9)

As with any crop, weeds and other competition must be removed to maintain growth and vigour in the plantation. Methods include manual, mechanical and chemical tending.

(i) Manual Tending

A small area, such as a nursery or a mini-orchard, may be tended by hoeing by hand around every tree, a very labour intensive job. Keep each tree clear for at least one square meter (nine square feet or three feet by three feet). Extend to four square meters (eighteen square feet) as the tree matures.

A vinyl or wood-chip mulch placed between the rows in a nursery, or covering a nine square foot area around each tree also helps. Non-biodegradable plastics which allow water to filter through are useful.

(ii) Mechanical Tending

Machinery designed to cultivate soil is effective but may damage tree roots near the soil surface (feeder roots).

Discs, harrows and shallow rototillers, either tractor-powered or as separate small units, can be used. Cultivate as required but be sure no annual or perennial weeds are allowed to go to seed. Rhizomous grasses, such as quack grass, love cultivation and are difficult to eradicate. If wide spacing is used, dual-crop or maintain a mowed interspace.

(iii) Chemical Tending (5) (6) (9)

Chemicals, if properly applied, do an excellent job of weed control. If the area is properly site prepared (all weeds removed), tending is usually not difficult with chemicals. The cost may be a deterrent on a large area, so dual cropping may be the answer. Chemicals such as Roundup and Simazine are standard, approved products for tree culture. Roundup is degradable on contact with the soil, kills most weeds and rhizomous grasses, and is applied only once or twice as a directed spray. Simazine is applied to stop germination of weed seeds already in the ground. Annual application is usually required, but soil buildup is a possibility. Use this product for a few years after plantation establishment and carefully monitor results. Other products like Goal, Poast, Fusilade, Dacthal have possibilities.

The Use of Fertilizers and Mulches (1) (8)

Test your plantation soil for soil deficiencies once a year. The Ontario Ministry of Agriculture and Food (OMAF) provides a free soil testing service. Simply request their soil sampling kit from your local OMAF office, follow the instructions on taking samples, send in the samples, and the results will sent back to you. This service can be used once a year.

Also, monitor tree performance for off-colour foliage, poor shoot growth, insect and disease. These symptoms indicate declining tree performance that may be due to soil deficiencies. Nitrogen and potassium, as well as trace the elements boron, zinc, and copper, are all essential in the right proportions to good health.

Apply fertilizer in the form of commercial products or well-rotted manure. A 10-10-10 fertilizer is broadcast under and somewhat beyond the spread of the tree branches in the spring. About one half kilogram per three centimeter (ten pounds per inch) of tree diameter is the appropriate amount. Do not apply later than July 15th as the stimulated late growth may be frost killed in the fall. Dormancy is expected at least five weeks before the first killing frost.

Proper weed control will ensure that all soil nutrients are available to the tree. A green manure such as rye or buckwheat could be established and tilled in prior to planting the tree. A wood chip mulch, not exceeding five centimeters thick, retards weed invasion and beneficially keeps the root cool in summer. Other organic growing methods can apply to nut trees.

Nut Tree Pruning (1) (8)

As with any orchard crop, pruning is essential for promoting tree vigour and form. A strong framework must be encouraged to develop in order to support the weight of the nut crops and to resist breakage from wind, ice, etc.

In general:

  • Avoid narrow branch angles;
  • Avoid narrow angles where main trunk divides;
  • Space scaffold branches on the trunk so that no two are at the same level.

Start corrective pruning at an early age so that rodent guards may be applied to the trunk and the desired tree form initiated. All pruning cuts are to be made close to the trunk, but not so close as to damage the branch collar. Pruning should be done early in the summer, after the spring sap run is well over, in order to avoid sap bleeding.

If timber is an objective, prune the branches before they reach two inches in diameter. Attain a height of nine feet or more for veneer logs. Seventeen feet is usually the preferred height for quality timber.

Plantation Protection (1)

Once the young trees are in place, routine protection will be required to minimize damage by rodents, insects and disease.

(i) Protection from Rodents.

Rabbits, mice, and meadow voles are the chief threat to young trees. After the bark heavily fissures, these are usually not a threat. Apply repellants to young trees if tree guards cannot be used. Do this immediately after planting.

Tree guards should be applied as soon as possible to a height of about one meter (at least thirty inches) up the trunk. Apply repellants to any low branches which can be reached by rabbits on the snow. Baits properly applied may be useful. Construct owl and hawk perches to attract these predators. Mow vegetation short so no cover is available to the rodents.

(ii) Protection from Harmful Insects. (1) (4) (11)

Insect populations should be monitored frequently. Defoliators such as caterpillars can be seen and sprayed as required. Scales, aphids and mites are more invisible so any decline in shoot vigour or leaf colour should be checked immediately. Integrated pest management (IPM) techniques can be used.

Defoliators - can be controlled chemically with Malathion, Diazinon, Bacillus thuringensis (B.T.), etc.

Sucking insects - control with dormant oil, miticide, Malathion applied according to the directions on the label.

Insects to watch for: Fall webworm, Eriophyid mites, Walnut caterpillar, Walnut aphid, Gypsy moth, Lecanium scale, Twig pruner, Husk maggot, Walnut weevil, Spider mites.

(iii) Protection from Diseases.(1) (4) (11)

Diseases are not common on nut trees, except possibly the walnut blight, anthracnose, and bunch disease. This causes early leaf drying and shedding. Both walnut and butternut are susceptible. Spraying with a good fungicide may be desired, such as Captan, Benomyl, lime sulphur or bordeaux mixture 4-4-100 may be desirable.

(iv) Protection from Larger Animals

Trees are sometimes attacked by deer, beaver, rustlers and porcupine. These animals may be stopped by direct means such as fences, trapping or elimination. However, there is no known universal solution to these problems.

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