Dec. 2, 1920.] Agricultural Gazette of N,S.W. 865 



Banana Root Borer 



{Cosmopolites scrdidus Germar). 



T. McCarthy, Assistant Entomologist. 



As in many other places where the banana is now extensively grown, the 

 banana root borer Cosmopolites sordidus has been introduced into the Tweed 

 Eiver district. It was first brought under notice fou* years ago, but was 

 probably introduced earlier in banana suckers obtained from Queensland, 

 where it has been known for at least twenty-five years. It has not thus far 

 been responsible on the Tweed for such considerable damage as it is said to 

 have done in Fiji. At present there is no general infestation in the Tweed 

 Eiver district, the beetles being confined to isolated areas, practically all of 

 which have been infested by the planting of beetle-infested suckers. 



The original home of the beetle is unknown, but it is not a native of 

 Australia. It was first described by Germar from Java in 1824 as Calandra 

 sordida, but Chevrolat in 1886 established the genus Cosmopolites for this 

 species. It is widely distributed in the tropics, having been recorded from 

 Lower Congo, Madagascar, Mauritius, Seychelles, Ceylon, India, Malay 

 States, Saigon, China, Java, Sumatra, Borneo, New Guinea, Fiji, Brazil, 

 Trinidad, West Indies and Florida. 



According to literature published, the banana beetle appears to confine 

 itself almost wholly to bananas, though Newell states that it also attacks 

 sugar-cane. All varieties of bananas are attacked. Jepson states that the 

 borer does not display more partiality for one variety than another, but in 

 St. Lucia, Dr. Hutson states it seems to prefer the plantain, the cultivation 

 of which is being abandoned there for another variety in the hope that it 

 may be less susceptible to the attacks of the beetle. No choice is, however, 

 available on the Tweed River, as the Cavendish banana is practically the 

 only variety grown. 



Character of the Injury. 



The injury is caused by the larva or grub of the beetle feeding and tunnel- 

 ling in the root-stock or bulb of the banana. (Plate II, Fig. 10.) The 

 greater part of the damage occurs in the outer part of the bulb, where are 

 located the fibro-vascular bundles which convey the nourishment to the 

 growing parts of the plants. The normal supply of food to the plant is 

 thus obstructed, and the growth of the suckers arrested, causing the leaves 

 to die prematurely, and finally the roll of unopened leaves or the growing 

 point of the plant to wither, as is shown in the illustration on page 866. 

 The tunnels, which are roughly circular, are at first small, but as the grub 

 feeds it increases in size, and the tunnels are enlarged accordingly until 

 they attain a diameter of about one-quarter of an inch. Eventually the 

 bulbs become riddled with these circular tunnels, permitting the invasion of 

 fungus and bacteria, which soon reduce the whole bulb to a blackened mass 



