56 Journal of the Department op Agriculture. 



In all probability the balance of nature will be restored sooner or 

 later. Tlie natural enemies of the rats will be attracted by the 

 abundance of their prey, and in the presence of an ample food supply 

 they in turn will breed up and eventually restore the rodents to their 

 original numbers. But in the meantime something has to be done to 

 check the damage. 



The chief object of the writer's visit to Umfolozi early in Novem- 

 ber last was to try out a virus kindly supplied by the Union Com- 

 merciale, Smith Street, Durban. This virus is manufactured by the 

 Pasteur Institute, Paris; it is sent out in tubes and known as " Pate 

 Verte." It is said to have been highly effective against rats in the 

 trenches during the late war. The application of the virus is very 

 simple ; it has to be spread on bait and placed where the rats can get 

 at it and devour it. 



Two dozen field rats were captured and placed in a large 

 roomy cage. Every day for a week these rats were fed 

 on short lengths of sugar-cane smeared liberally with the 

 virus. They ate the cane quite freely, yet at the end 

 of the week all were as healthy and happy as some others 

 which were not fed on the virus. Either these particular species 

 are immune from tlie organisms which are pathogenic to ordinary rats, 

 or else the virus had lost its virility owing to its age. One of the first 

 essentials in using a virus is to obtain it as fresh as possible, otherwise 

 the disease-producing organisms may die out or lose their virulence. 

 The virus used at Umfolozi was at least two months old, and this may 

 have been the cause of its failure to act. 



Several Poisox Baits 



were tried on other caged rats to see if a bait could be 

 found which was more attractive than sugar-cane. The poison 

 used in every case was a sweetened 2 per cent, solution of 

 strychnia hydrochloride. Extensive experiments in America have 

 proved that strychnine is about the best poison to use in the destruction 

 of rodents. The soluble hydrochloride was used as it is more easily 

 applied to the baits in the form of a solution than the insoluble strych- 

 nine crystals. Raisins, slices of potato, sweet potato, carrot, and short 

 lengths of fresh cane were soaked in the 2 per cent, solution for an 

 hour or so and then placed in the cages with the rats. Next morning- 

 twelve out of the twenty rats were dead and during the day seven more 

 died leaving only one alive. The raisins, potato, sweet potato, and 

 carrot had been left severely alone, but the cane had been freely eaten. 

 Thus it was found easy enough to destroy cage specimens but the 

 application of the bait under field conditions was a different matter. 

 The poisoned cane could not be scattered broadcast owing to the danger 

 of oxen finding it and eating it. It was also found impracticable to 

 search for the holes and place the bait down each hole owing to the 

 dense growth of the older plantations and the thick covering of dead 

 foliage. 



A third method that was tried seemed more hopeful. It is the 

 practice of the planters to burn the trash and dead vegetation before 

 cutting their cane. By surrounding a field as it was being burnt it was 

 found that very few rats were driven out by the fire and still less were 

 found dead after the fire. Thus it was concluded that they were all 



