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Organisation: United States Department of Agriculture (USDA)
Author: Joe E. Brooks and Lynwood A. Fiedler
Edited by AGSI/FAO: Danilo Mejia (Technical), Beverly Lewis (Language&Style), Carolin Bothe (HTML transfer)

CHAPTER III Vertebrate Pests: Damage on stored foods

4.1 Sanitation and good housekeeping

4.2 Denying rodents access to foods

4.3 Eliminating or reducing rodent numbers

4 Management of rodent populations

The prevention of losses of stored foods due to rodents by subsistence and small-holding farmers comes down to relatively inexpensive methods that the farm family can afford. These consist mainly of three things: 1) sanitation and good housekeeping, 2) denying rodents access to stored foods, and 3) elimination or reduction of rodents in the farm structures.

4.1 Sanitation and good housekeeping

Sanitation and good housekeeping in small-holding farmers housing structures means keeping all spilled grains swept up daily, not allowing food scraps to accumulate, and keeping the cooking area and cooking utensils and pots clean every day. It means sweeping the floors of the living quarters and the cooking area daily; keeping grains, vegetables, fruits, spices, and herbs used in daily food preparation in tins, jars, or earthenware containers when not in use, to prevent rodents from eating them.

All vegetation near the farm structures should be keep cut away from the buildings, especially any fruit trees or vines. Vegetable gardens should be planted away from the living quarters. Nearby grassy and weedy areas should be kept cleared.

Whenever grains are put outside for drying or winnowing to remove seeds, stems, stones and dirt, the area should be thoroughly swept after these tasks are finished. f grains are threshed in the farm compound, the area should be swept to recover all grains.

If livestock are kept in the farm structures, such as goats, sheep, or cattle, the family members should keep the animals' area clean and especially to keep any uneaten food swept up and disposed of by burying or burning.

4.2 Denying rodents access to foods

Keeping rodents out of stored grains may be difficult, especially if the amounts to be stored for even a month or two approximates 1,000 kg, the harvest from a half to one hectare of land. Much of the grain is stored in jute bags, woven baskets, or open cribs. None of these will keep rodents from the foods. Wire mesh, metal and ceramic containers, or brick and concrete bins are needed to keep rodents out. These items, unfortunately, are expensive and usually beyond the reach and pockets of subsistence and small-holding farmers. A collective or co-operative venture, whereby several farmers pool their resources and store their grains collectively in a structure especially made for that purpose, may be tried. This venture would require an unusual degree of Cupertino among neighbours, however, and could easily be subject to dispute as to amounts placed and withdrawn from storage. Some co-operatively agreed authority would have to record carefully the amounts of grain stored and to control and account for withdrawals.

Metal-covered wooden bins may be made to hold grains, using the metal from old kerosene tins to cover the exterior. Or discarded metal food tins may be flattened and used to rodent-proof a wooden bin. If wire mesh is available, this may be used instead of metal tins.

Care must be taken to cover all surfaces and not leave any gaps between overlapping pieces of mesh or metal. Rust is an ever-present possibility and so galvanised or tinned metal should be used if available. Otherwise, several coats of paint may retard rusting in the tropics.

The average farm family needs to protect the seed grain for the next planting very carefully. This can be done by storing it in small ceramic or metal containers with tight- fitting lids.

If the farm family keeps chickens, ducks, or pigeons, these should be maintained where rodents would not have access to their foods or food scraps, nor to their chicks or eggs. The birds should be penned at night in cages made with wire mesh too small for rodents to climb through. All excess uneaten foods or food scraps should be cleaned daily after the birds have been fed and buried or burned.

4.3 Eliminating or reducing rodent numbers

Rodents living in farm structures may be killed or their numbers reduced by destroying their nesting places in the roof or upper beams of the buildings. These areas, where accessible, should be sought out and the nests actually physically removed. This will not drive the animals out of the structure, however; the rodents may be killed with sticks when disturbed or dislodged from their harbouring places. If burrowing rodents are present in or around the farm structures, their burrows should be dug up and destroyed and the rodents killed when disturbed. If the farm family can afford even one trap, this can be set nightly for a number of weeks and should eliminate most rodents from the structures. Another form of trapping is the use of glue boards. These are squares of heavy cardboard that is covered on the upper surface with a vert sticky adhesive that entangles the feet and fur of any rodent venturing onto its surface. The rodent then is killed with a stick and disposed of and the glue board set again. Rain, dust, and dirt on the glue board will make it ineffective.

Medium-income farm families may be able to afford the use of poison baits around the farm structures, in addition to all of the steps given above. The use of poisons around the

household will have to done very carefully, however, to prevent the poisoning of children and household pets and domestic livestock. Baits should only be used in covered containers into which a child, chicken, pigeon, cat, or dog cannot gain access to the poison. All baits should be placed out of sight, and on the ground or floor level. All poison baits should be used only in a manner consistent with the label directions.

The few rodenticides that can be used by farm householders are the anticoagulants and zinc phosphide. The several anticoagulants that may be available in developed countries consist of baits incorporating warfarin, coumatetralyl, diphacinone, chlorophacinone, brodifacoum, difenacoum, bromadiolone, flocoumafen, or difethialone at several concentrations.

Anticoagulants: Anticoagulants are mixed with baits in very small amounts, varying from 0.0375 percentage to 0.005 percentage concentrations. These baits do not kill quickly; instead they must be eaten by the rodents for several days and then the clotting ability of the blood is reduced, causing death by haemorrhage. In general, the spiny mice are very little affected by anticoagulants, so these are not recommended for their control. Also, the earlier anticoagulants (warfarin, coumatetralyl, diphacinone, and chlorophacinone) are relatively slow to kill roof rats and house mice; up to 21 days may be required to kill off most mice. To eliminate these species, the "second-generation" anticoagulants (brodifacoum, difenacoum, bromadiolone, flocoumafen, difethialone) should be used. Baits for household rodents should preferably be placed in bait containers or under cover where children and domestic animals will not have access to them. A surplus of bait should be maintained at the baiting sites for up to 10 days. Then all uneaten baits should collected and disposed of by deep burial. Zinc phosphide: Zinc phosphide is mixed with bait materials at usually a 2 percentage concentration. This material is hazardous to humans and all domestic animals, including chickens, so should be used with extreme care by the householder. Baits should preferably be used in bait containers or at least placed under cover where children and domestic animals do not have access to them. Zinc phosphide kills rodents quickly; most animals that eat enough of the bait will die within 8 to 24 hours; some may die on or after the second day of baiting. After placing baits out for a few days, all uneaten baits should be retrieved and buried several feet in the ground. Generally after two or three days, all baits that weren't eaten in the first few days will be rejected by any surviving rodents. Zinc phosphide should be effective against all pest rodent species previously mentioned in this chapter.


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