Method for Combatting Rodents and Rodenticidal Compositions

Heretofore, various rodenticides, in particular raticides have been developed. They are, however, linked with toxicity to men and cattle and their repelling property and any one of them are not satisfactory yet. For example, N-(1-naphthyl)thiourea, which is now widely used under the trade name "ANTU" have the disadvantage that, although of relatively low toxicity to human being, it will repel, once it is used, the rats in the applied area and prevent their access for bait over a considerable length of time.

We have made extensive research for those rodenticidal compounds eliminating these drawbacks and now found that compounds of the above-described general formula (1) have strong toxicity to rodents and relatively weak repelling property to maintain good rodents' access for bait, while having low toxicity to useful animals such as dogs, on which finding the present invention has been achieved.

Compounds used in the present invention may be prepared for example, by adding the corresponding aniline to a solution of benzoyl chloride and ammonium rhodanide in acetone, and boiling the mixture to condense the reactants. They may also be prepared by condensing phenyl isothiocyanate with the corresponding amine in the presence or absence of an appropriate solvent. Alternatively, compounds of general formula (1) wherein R.sub.3 and R.sub.4 are both hydrogen may be prepared by hydrolyzing a corresponding phenyl-3-benzoylthiourea with an aqueous sodium hydroxide solution. Acid addition salts include salts with hydrochloric acid, sulfuric acid and the like.

Compounds of general formula (1) used in the present invention may be applied by itself for combatting rodents by applying them to passages of rodents, but normally they are used together with adjuvants and a composition of the compound with adjuvants (for example carrier etc.) may be applied for combatting rodents by any suitable means, as by applying the composition to passages of rodents or by placing the composition as bait or poisonous drinking water where rodents are accessible to the bait or water.

As carrier, one may employ, for example, solid materials such as starch, kaolin clay, montmorillonite clay, diatomaceous earth and sugar, liquid materials such as xylenes, chlorobenzenes and the like aromatic hydrocarbons, methanol, ethanol and the like alcohols, ethanolamine and the like amines, aliphatic esters and water and favourite diets of rodents such as meats, meat extracts, rice, wheat flour, buckwheat flour, corn flour and the like cereals, sugar-cane, potato, seeds of sun flower, fish meal, fruits, vegetables and the like.

Compositions of the present invention may be used as rodenticidal compositions in form of powder, granules, pellets, solution, suspension, emulsion, paste and the like convenient form, optionally with the aid of an adjuvant such as carrier an emulsifying agent or a dispersing agent.

As emulsifying agents, one may employ, for example, nonionic and anionic emulsifying agents such as fatty acid ester or phosphoric acid ester of polyethylene glycol. As dispersing agents, one may employ, for example, calcium sulfonate.

The rodenticidal composition of the invention normally contains a compound of general formula (1) in concentrations of from 0.05% to 95%, preferably from 0.5 to 90% by weight.

Rodents which can be combatted according to the present invention include rats (Genus Rattus) and squirrels.

Representative examples of active compounds used in the present invention are given in Table 1.

The following experiments illustrate that the active ingredient according to the present invention has excellent rodenticidal effects.

A 3% starch solution was prepared, boiled and cooled and a given amount of a compound of general formula (1) was suspended therein. Test Norway rats were each orally given 2 ml of the suspension and then fed. After 5 days, inspection was made whether the animals survived or died. The results are shown in Table 2.

A single Norway rat was housed in each test cage (25 cm width .times. 35 cm length .times. 20 cm height) and was fed overnight by placing in the cage 10 g of a bait containing the active ingredient as prepared by the method described in Example 3 in a concentration of 1.0%, with said bait contained in a tall-skirted Petri dish. Inspection was made for the amount of the bait eaten (bait intake) and for the fatal effect of the active ingredient during 3 days. The results are shown in Table 3.

A wire netting cage of 30 cm in width, 90 cm in length and 60 cm in height having a nest box placed in it and another wire netting cage of 90 cm in width, 90 cm in length and 60 cm in height where water and diet were placed were brought into tight contact with each other, and connected through a 10 cm .times. 10 cm gateway through which a tunnel of 20 cm in width, 30 cm in length and 20 cm in height was provided. On the bottom surface of the tunnel was placed a vat of 20 cm in width and 25 cm in length scattered with a tale-based powder preparation containing the particular compound (Compound No. 2) in a concentration of 10% as prepared by the method described in Example 1 Test animals (1 male, 3 females, 4 animals in all, total body weight 790 g, mean body weight 198 g) were released in the cage. It is understood that the animals will walk on the powder-sprayed surface at every egress and ingress. Inspection was made for daily diet intake, the amount of the powder preparation consumed and the number of death. The results are shown in Table 4.

A single brown rat was housed in each wire netting test cage of 25 cm in width, 25 cm in length and 35 cm in height, fed overnight with 10 g non-poisonous feed as prepared by the similar method described in Example 3 contained in a tall-skirted Petri dish and further fed overnight with 10 g bait containing the active ingredient [Compound No. 2 or "ANTSU" (Trade name)] contained in a tall-skirted Petri dish. Feed or bait intake was examined in the respective cases. 20 Norway rats were used for each of the active compound containing baits.

The repelling property of the respective baits were evaluated by the relative repellency which is defined by the following equation: ##EQU1##

The results are shown in Table 5 in which the numerical values for relative repellency are averaged ones.

Cream bun was cut into pieces as large as hen's eggs and the pieces were provided in the central portion thereof with a hollow. To this hollow was added milk together with Compound No. 2 to embed the latter in the hollow. The cream bun pieces thus treated were given to dogs by hand. The results are shown in Table 6.

A single Norway rat was housed in each of test cages of 25 cm in width, 35 cm in length and 20 cm in height each, and fed overnight with 10 bait as prepared by the method described in Example 3, containing the stated compound in a concentration of 1.0%, while keeping the bait in a tall-skirted Petri dish. The bait intake and the fatal effect within 5 days were examined. The results are shown in Table 7.

The present invention will be further explained with some of the compounds according to the present invention. It is understood, however, that the contents of the active ingredients and additives may vary over a wide range. In these examples, all percentages (%) are by weight.

are admixed to give a powder preparation.

are admixed and 10 parts of the admixture is sprinkled on 100 parts of sweat-cane, potato, bread or fried beancurd to give a bait.

are admixed and 100 parts of the admixture is kneaded with 20 parts of water added and formed into cylindrical granules, which are then dried to give a bait.

are admixed and 10 parts of the admixture sprinkled on 100 parts of sweat-cane, potato, bread, fried beancurd or the like to give a bait.

are admixed to give an aqueous bait.

are kneaded and formed into doughboys each weighing 0.5 g to give a bait.

Powdered Compound No. 8 is applied as such to a passage of rats.

Powder of Compound No. 8 is applied to sweet potato cut into cubes 3 mm cube in a manner such that the content of said compound may become 1 %, to give a bait.

Grains of wheat are dipped in a 10 % aqueous sugar solution and powder of Compound No. 2 sprinkled on the solution to give a bait.

20 parts of water is added to 100 parts of corn flour and kneaded therewith and 10 parts of powder of Compound No. 3 is admixed with the dough to give a bait.

1 part of powder of Compound No. 6 is suspended in 100 parts of an edible oil to give a bait or a sprinkling composition.

Powder of Compound No. 8 is sprinkled on bread impregnated with a 10 % aqueous sugar solutions give a diet.