Rats in Sugar-Cane. 55 



RATS IN SUGAR-CANE. 



By S. H. Skaife, M.A., Entomologist, Scliool of Aorioiilture, Cedara. 



?\[atal. 



On tlie whole the siig'ar ])J a liters in South Africa are singularly 

 fortunate in having very few pests of importance to contend with. 

 Compared with the conditions found in other sugar-growing countries, 

 the plantations liere are remaikahly free from su('h trouhles as fungous 

 diseases, borers, mealy-hug, froghoppers, etc. Recently, however, the 

 sugar farms on the Unifolozi Flats have suffered severe losses from the 

 depredations of rats. 



The rats in question are not the cane rats proper, Thryonomys 

 swinderenianus , but four or five different species of ordinary field rats. 

 They are present in enormous numbers in fields of cane ten months old 

 and older. Cane younger than ten months is not troubled much by 

 these rats as it does not seem to afford them enough slieltei; against 

 owls and hawks. The rats are found on all the farms along tlie banks 

 of the Umfolozi River, but in most cases the damage is moderate com- 

 pared with what is found on two or three farms along the north bank. 

 On these farms the rats teem and cause great damage by gnawing 

 through tlie base of the cane, causing it to fall and dry out. Mr. Jack 

 Martens, of River View, whose farm is perhaps the worst infested of 

 all, was cutting during November last (on the occasion of the writer's 

 visit tliere) only seven tons of cane to the acre instead of an average of 

 thirty-five tons. 



The rats causing the trouble are nearly allied to the common house 

 rats and resemble tliem closely in general appearance. They are 

 apparently widely spread in South Africa, yet it is seldom we hear of 

 them causing such serious damage as related above. They are reported 

 to be giving trouble at Enifjangeni, not as a pest of sugar-cane, but as a 

 nuisance in a cotton field where they robbed the bolls as soon as they 

 were open, removed the seed, and lined their nests with the fibre. 

 An experimental plot of cotton on Mr. Duncan's farm, at Umfolozi, 

 was treated in exactly the same manner, and although the plants did 

 well, there was no cotton to be gathered as the rats took it all. 



The trouble at Umfolozi seems to be entirely due to an upset in 

 the balance of nature. The farms in this district suffered severely 

 from floods in February, 1918, and the jilanters state that hundreds of 

 snakes were killed by these floods. Formerly snakes were very common 

 in the plantations but now they are seldom seen. Thus the rats were 

 rid of one of their chief enemies and consequently have been able to 

 breed enormously under the ideal conditions of an abundant 

 food supply, ample shelter, and freedom from persecution. Hawks 

 and owls abound, but as the rats make their homes amid the dense 

 growth and thick trash of the older fields they are practically immune 

 from attacks by these enemies. The theory that the present outbreak 

 is indirectly due to the floods is borne out by the fact that the worst 

 infested farms are those which suffered most from the floods. 



