The cost of rat proofing the entire premises of many American farms would amount to less than the loss occasioned by rats on the same farms during a single year. In no other place is rat proofing more badly needed or less often accomplished than on the farm. There are, however, numerous examples of rat-proof farms in nearly every county in the United States, and almost invariably they are the more prosperous farms, for the rat proofing of a farm is an indication that the farmer has learned the necessity of stopping all small leaks, which mean reduced profits.

A rat-proof farm is not necessarily one in which the entire farmstead is absolutely proofed, but rather one where conditions are so unfavorable for any invading rats that they either will desert the premises of their own accord or may be easily routed by man or dogs. The source of the trouble on almost any heavily rat-infested farm can be traced directly to conditions that furnish rats safe refuges near abundant food. The commoner of these rat-breeding places are beneath wooden floors set a few inches off the ground in poultry houses, barns, stables, granaries, corncribs, and even residences; in piles of fuel wood, lumber, and refuse; in straw, hay , and manure piles that remain undisturbed for long periods beneath concrete floors without curtain walls; and inside double walls of buildings. In rat proofing the farmstead as a whole, attention should first be paid to the premises outside the buildings and later to each building separately.

Neatness is of prime importance in keeping a place free from, rats, and providing facilities for keeping it neat should be considered part of the rat-proofing program. An incinerator, which can be made from a discarded metal drum or rolled-up poultry netting, is convenient for burning all trash and combustible waste; and a deep, covered pit with a trapdoor will take care of tin cans and other noncombustibles, if it is not practicable to haul them away at regular intervals. A covered garbage can is also indispensable on farms where table scraps are not fed directly to poultry or hogs. (Fig. 1.) Raised platforms, 18 or more inches high, should be provided upon which to pile lumber or other materials that if placed on the ground would afford shelter for rats. (Fig. 2.)

Large piles of cut stove wood on many northern farms become rat infested. The same is true of manure piles adjoining barns and, to a lesser extent, of hay and straw stacks near farm buildings. These do not provide food and are attractive to rats for harbors only if near a source of food supply; moving them to a place at some distance from where foodstuffs are handled will usually solve the problem.

Stone walls at times furnish excellent harborage for rats but, like the woodpile, only if there is ample food near by. Stone walls supporting embankments and driveways on sloping farmsteads are most frequently infested, and when this occurs the inviting openings can usually be readily closed with small stones and cement.

Ditch banks often are a source of rat infestation, but in most climates during the warmer months only. The rodents concentrate in such places because they are less likely to be disturbed there. Rat proofing the ditch bank consists merely of burning or otherwise destroying the protective vegetation. This, of course, affords only temporary relief and should not be considered strictly rat proofing.

The use of concrete in the construction of most farm buildings is usually the best means of permanently excluding the rat. Fortunately, many of the fundamentals of rat proofing are also principles of good construction. As am example, in order to support a building properly, the foundation should extend well into the ground below the frost line; rat proofing likewise requires that the foundation wall extend at least 2 feet below the surface. Rats seldom burrow deeper than 2 feet unless natural passageways assist. Foundation walls should project a foot or more above the ground in order to protect the wooden parts of the building, and this also lessens the opportunity for rats to gnaw through the wall. A rat is not likely to cling to the exposed exterior of a building a foot above the ground while it gnaws a hole through wooden sheathing or siding. It would do so very quickly, however, if such siding extended to the ground, where its work could be under cover of vegetation or behind some object, particularly when the siding becomes somewhat rotted, as would soon happen were it close to the ground.

It is important that concrete be hard, as weak concrete is but a slight obstacle to the sharp rodent incisors. The mixture approved for ordinary building construction, however, is sufficiently hard to be entirely rat proof, and it is essential that approved practices of mixing and placing concrete be followed. Directions for using concrete and for building concrete floors are given in Farmers' Bulletin 1279, Plain Concrete for Farm Use, and in Farmers' Bulletin 1480, Small Concrete Construction on the Farm. Other approved building practices, such as fire stopping double walls, eliminating waste dead spaces, making doors, windows, and ventilators fit tightly, and screening or permanently stopping all openings, are also necessary in rat proofing. For simple farm buildings the foundation illustrated in Figure 3 meets all the requirements of good construction and will keep the rats out if the walls are tight.

BARNS

It is seldom possible to shut out rats completely from barns or entirely to cut off their food supply where livestock is fed. Little trouble will be experienced with them, however, if their harbors are eliminated. In barns rat harbors are most frequently found around stalls, under wooden mangers, and stall partitions, and beneath wooden or dirt floors. In modern barns with concrete floors, concrete or metal mangers, and metal stanchions, such places of retreat are entirely eliminated. In older barns it is desirable at least to replace wooden and dirt floors with concrete and reconstruct the mangers so that they are a foot or more off the ground.

Another common source of rat trouble, particularly in the northern half of the United States, is the hollow wall, within which rats find safe retreat and convenient runways leading to the haymow. In recent years fibrous insulating materials have been used to line the interiors of many farm buildings, and in most cases these have resulted in greatly increased rat infestation. Rats cut through these composition boards very easily and seem to be attracted by the facilities for breeding thus provided. Hollow walls of any kind accessible to rats should either be eliminated or adequately rat proofed. Such rat proofing may be accomplished by filling the hollow spaces to a height of 8 or 10 inches above the sill with cement, bricks, or other material resistant to the gnawing of rats, or a strip of galvanized metal 2 or more feet wide may be carried around the inside wall just above the sill.

Old barns with wooden floors supported a few inches above the ground on girders and posts are particularly objectionable from the standpoint of rat infestation and should be rat proofed with concrete. (Fig. 4.) A concrete foundation wall extending at least 2 feet below grade is placed under the girder between the posts. The wooden posts may be removed after the wall has hardened, and the spaces left should then be filled in with concrete. A concrete floor is laid, and cement stucco on metal lath is extended up the walls for at least 2 feet, preferably to the level of window sills.

Rock foundations in many old barns offer excellent harborage for rats unless pointed carefully with cement mortar. If possible, the floor should be raised to the level of the sill and the walls plastered to the window-sill level (fig. 5) in such manner as to prevent access by rats to spaces between the studs.

The grain bin and other similar fixtures must always be considered in rat proofing a barn. It is most important that they be so situated or constructed that there shall be no hiding places for rats behind or under them. The grain bin should be completely lined or covered with metal and should have metal-clad lids. Any open spaces behind or under the bins should be tightly closed with metal. (Fig. 6.)

Other accessories of various kinds of barns should be examined carefully and remodeled or moved if necessary to exclude rats or eliminate harbors. The haymow frequently presents a difficult problem in a heavily infested barn, but the haymow alone is seldom responsible for the rats, for if all other rat harbors in the barn are effectively eliminated or shut off, the rats will not long remain with the hay as their only shelter. If the lower walls are of rough surface or composed of open studs covered on the outside, rats can climb at the corners. They may be prevented from doing so by the application of a strip of metal 8 inches wide placed just below the joists of the upper floor. Recommended construction of walls and floors in new frame barns is shown in Figure 7.

CORNCRIBS

Of all the buildings on the average farm the corncrib is usually in greatest need of rat proofing. Losses sometimes amounting to a fourth or a third of the total quantity of corn held over winter have been known. A survey in a southern State showed an average loss of 5 per cent of corn in storage; in one case 500 bushels were destroyed in one crib during one winter. The amount of this loss would have been sufficient to pay for rat proofing the crib several times over. In building or remodeling a corncrib; therefore, it is most important that it be made permanently rat proof. Probably the most satisfactory method of accomplishing this with the common slat-sided corncrib is entirely to cover the walls and ceiling on the inside and the wooden floors on the under side with woven-wire mesh or hardware cloth, two or three meshes to the inch. A heavy grade of woven wire should be used, 12 or 15 gage, and galvanized after weaving. Painting with a tar or asphaltic paint increases its durability.

Another method, and one that is less expensive and quite effective as long as kept in good repair, is shown in Figure 8. Wire netting should be carried around the entire crib to a height of 2 feet or more from the top of the foundation. A strip of galvanized iron 8 inches wide should be fastened above the wire netting. The joints between the foundation and netting and between the netting and metal strip must be tight. As rats are unable to gain a footing on the smooth metal and can not climb over it, it is unnecessary to use wire netting above the strip. Care should be taken to join the lengths of metal tightly and to carry the wire netting and strips of metal across and around both sides of doors and door jambs. It is also advisable to provide doors with springs or weights to insure their remaining closed.

If possible the corncrib should have a concrete foundation and floor, as illustrated. Otherwise it should be elevated on posts or piers so that it will have a clearance underneath of feet or more. If the supporting posts or piers are covered with sheet metal, or are protected at the top with metal collars or disks extending at least 9 inches out from the posts, rats will be kept out of the crib. Old cribs can often be rat proofed in this manner at little expense. Dish pans and washtubs make convenient rat guards. (Fig. 9.) It is important that the area beneath the corncrib be kept clear and that nothing that the rats can climb be leaned against it.[1]

GRANARIES

The rat proofing of granaries is of great importance, because of the abundance of food stored there and the corresponding opportunity for serious loss. The granary with concrete foundation and floors, tight-fitting doors, and screened ventilators presents no unusual problem, except possibly in connection with the elevator pit, which should be carefully checked against possible means of ingress for rats. Small wooden and portable granaries should be protected with wire netting. (Fig. 10.)

Concrete feeding floors, troughs (fig. 11), water tanks, hog wallows, and similar structures should be constructed with a curtain wall, or apron, around the outer edge extending 2 feet or more into the ground (fig. 12) to keep the rats from burrowing underneath the slab. This also tends to prevent the heaving caused by frost and the uneven settling of the structure in soft ground.

POULTRY HOUSES

It is not practicable to attempt to exclude rats from poultry houses, but such buildings can easily be made proof against serious trouble by the elimination of all places where the rodents can obtain safe harborage. Most rat infestation around poultry plants is due to the presence of numerous shelters and suitable breeding places. Three things are particularly to be avoided: Wooden floors on or within a few inches of the ground; double walls; and nest boxes, feed hoppers, and other fixtures placed so as to provide shelter for rats under or behind them. From a rat-proofing standpoint the floors as well as the foundation should be made of concrete. (Fig. 13.) If this is not considered practicable, wooden floors should be elevated so as to insure a clear space of 2 or more feet between the floor and the ground. Warmth can be provided, if necessary, by two thicknesses of flooring with tar paper between. Hollow walls almost invariably furnish harborage for rats. The inner stud covering therefore, should be torn out, but if warmth is a factor to be considered, siding should be put over sheathing on the outside of the studs with building paper between.[2]

Portable laying and brooder houses frequently become heavily infested because they are usually built with wooden floors removed from the ground only by the height of the runners on which they are constructed and are seldom moved as frequently as originally intended. Feed, sifting through the floors, attracts rats, which after finding desirable shelter soon establish themselves in burrows beneath the houses and multiply rapidly. Portable houses, therefore, should be raised off the ground 2 or more feet.

Nests should be raised 2 or more feet above the floor, and feed and grit hoppers at least 1 foot. Drinking vessels for water and skim milk should supported on a platform 1 to 1½ feet above the floor, so as to eliminate the possibility of rat shelters and keep the liquids in a more sanitary condition. Other equipment should be given the same consideration.

The premises around the poultry house should be cleared of all rat harbors by elevating all objects under which a rat can find shelter. (Fig. 14.) Near-by buildings particularly should be considered, for it is frequently found that rats living exclusively on poultry feed occupy harbors 50 or more feet away from the food source. For this, reason it is desirable to build poultry plants at least 100 feet from any possible rat harborage. The vast number of young chicks killed annually by rats would be greatly reduced if these simple precautions were taken.

OTHER FARM STRUCTURES

There are many farm buildings of various kinds that should be made proof against rats. In most cases, however, the application of the general principles of rat proofing, as previously explained, will suffice. Not only should all buildings in which food is kept be made inaccessible to rats, but adjoining and near-by buildings and premises as well. The procedure to be followed in the case of farm dwellings is omitted here, as sufficient is included under the next heading, Rat Proofing City Buildings, the conditions with respect to dwellings on farms and in towns being quite similar.

Outside cellars frequently become infested with rats, and great havoc to stored produce almost invariably results. Considerable expense, if necessary, is justified in making the storage cellar rat proof. A cellarway with wooden steps and sills and earth floor is usually the source of the trouble. The sill soon rots or the rats burrow under it to gain entrance. The remedy is to construct a concrete floor and cellarway. This not only will exclude rats but will prove more economical in the long run. (Fig. 15.)