THE PESTS AND DISEASES OF THE CANE 145 



and emerges at night to attack the crop above ground. It only becomes 

 dangerous when for some reason the natural balance has been disturbed. 



Another widely distributed cricket, Gryllotal-pa africana, in addition to 

 feeding on the cane, does damage to irrigation ditches in the Hawaiian 

 Islands by means of its tunnels. 



White ants, Termes taprobanes, have been recorded in India by Hadi 37 

 as attacking seed cane and the young shoots after germination, and are 

 to be regarded as a major pest of that country. In Java the " thrips " or 

 " bladder feet," sometimes included in the orthoptera, have been observed 

 as a minor pest. 



Acarid Pests. Mites are a form of life frequently found on cane, but the 

 damage done is usually trifling. A serious amount of harm was done in 

 Queensland in 1876 by a mite, Tarsonymus bancroftii. 38 The disease was 

 then known as " cane rust." These mites are also present in Java and in 

 Barbados. To a certain extent they are to be considered beneficial, since 

 Ormerod has observed the parasitization of the eggs of the West Indian borer 

 by this form of life. 



Worms. Certain nematode worms have been recorded as attacking cane. 

 Of these there are Heterodera radicicola^ and Tylenchus sacchari in Java. 41 

 At one time these worms were thought to be connected with the Sereh 

 disease. More lately Cobb 42 has described a nematode, Tylenchus similis, 

 which he has observed as parasitic on the roots of sugar cane and banana 

 in both Hawaii and Jamaica. 



Insect Epidemics. In the history of the sugar cane are to be found 

 numerous instances of insect epidemics. In most of these there has been a 

 short period in which the presence of the insect was casually observed. 

 This has been followed by a period over which the damage occasioned has 

 been intense. Eventually the pest reaches a permanent endemic stage, 

 with irregular outbreaks of the. epidemic phase. This course of events 

 follows on certain " natural laws," discussed in another section. 



Of insect epidemics of greater interest, there may be recorded : 



1. In 1760 an extraordinary plague of ants, which has been described 

 by Castle 43 , appeared in the West Indies. Both Castle and Hughes 4 seem 

 to think that the ants were attracted as predators to the " blast " due to 

 aphides at that time prevalent on the cane. This " blast " is frequently 

 referred to by the early writers on the West Indies ; a yellow blast, probably 

 due to the aphis, Sipha flava, and a black blast, probably due to a second 

 aphis, Aphis setarice, were distinguished. 



2. In the early part of the nineteenth century much damage was done 

 by an asciracid, Delphax saccharivora. This insect had been present for 

 many years, and reached the epidemic stage about 1830, the destruction 

 of cane being particularly great in Grenada. 28 It still remains as a major 

 pest in Jamaica. 



3. The " pou-a-poche blanche " became exceedingly destructive in 

 Mauritius about i86o. 31 This epidemic was caused by a coccid, Icerya 

 seychellarum, a second coccid, Pulvinaria iceryi, being also present. Although 

 a definite statement is impossible, it is highly probable that this insect 

 arrived in Mauritius with canes imported from Australasia. 



4. About 1850 a very serious outbreak of " moth borer " occurred in 

 Mauritius. 14 It is almost certain that the pest in this case was introduced 



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