1 38 



Til K A i : KK'ULT URAL NEWS. 



April 24, 1915. 



INSECT NOTES. 



THE SWEET POTATO WEEVIL. 



(CYLAS FOBMICARIPS, FAB.) 



In accounts of the searabee or Jacobs of the sweet 

 potato (CryptorAynchus batatae) which have appeared 

 in tin- publications of the Imperial Department oi Igri 

 culture, mention has been made of the sweet potato 

 weevil (Cylas formicarius), and figtareshave beengiven show- 

 ing the difference in appearance between these two i 

 Thej are both weevils, in that they are beetles with the 

 front of the head prolonged to form a beak or proboscis, at 

 the extremity of which the biting 1 mouth parts an 

 Since the West Indian insect, Cryptorhynchus batatae, is 

 already well known and designated by its common names, 

 searabee and Jacobs, it will be sufficient to retain the name 

 ■ sweet potato weevil' as applying to the other species, Cylas 

 Jormkarius, which does not as yet occur in the Lesser 

 Antilles, so tar as the records of this Department show. 



distribution. Tin- sweet potato weevil is distributed 

 throughout the tropical and subtropical parts of the world, 

 and it is probably capable of living wherever sweet potatoes 

 are grown on a large scale. This insect was originally 

 described from the East Indies iii the 18th century, and as 

 a pest "i sweet potatoes it was recorded from Ceylon in 

 1856. It is likely that the species is a native of Africa 



since the genus Cylas is represented by a large number of 



specie, in that Continent, while very few occur elsewhere. 



I'll., o. sw I IT POT V.TO »il VII.. 



\,lnli. Pupa and Larva. (From U.S. Dept. Agric.) 



At the on sent time Cylas formicariu* occurs as a sweet 

 potato pest in [ndia and the Far Bast, in Africa, the United 

 States, Jamaic i, < luba, British ' luiana, and the Bahamas. It 

 is stated to have been recorded from Barbados, but it does 

 not appear to be known in that island at the present 

 time, nor indeed has it been known there for many years 

 past. This insect has been known and recorded as existing 

 in Cuba, Jamaica, British Guiana, and the United States, 

 but the present record of its occurrence in the Bahamas is 

 quite new. This record is based on the identification of 

 specimens received from the Secretary of the Hoard oi 

 Agriculture, Nassau, Bahamas, by the Imperial Commissionei 



of Agriculture for the West Indies. 



The sweet potato weevil would seem to be fully as 

 destructive as the searabee, and the injuries caused by it are 



f 

 iner 



very much like those caused by the searabee. Instances are 

 recorded in which entire crops ol sweet potatoes have been 

 destroyed by the sweet potato weevil. 



method ot in ok. The sweet potato weevil depo 

 eggs in the thickest vines near their base, and in the roots oi 

 the potato where these |re exposed at the surface oi the soil. 

 Once an attack has begun, that is, when the first infestation 

 has taken place in a'potato field, the development of the 

 weevil and its increase in numbers is merely a ma tier of time. 



The life cycl supies about thirty day-: the adults developing 



from the first infestation continue and spread the attack 

 throughout the field arid carrj it to the roots: each succeedi _ 

 generation greatly in< Peases the amount of injury, and it will 

 be seen that prevention ,,| the beginning oi the attack for as 

 long as possible after planting, and harvesting as soon as the 

 potatoes are ready, will do a great dial in reducing the amount 

 of injury. 



Minion in- iomiiiu.. The sweel potato weevil attacks 

 potatoes in the same manner, and the damage caused by it is 

 of the same kind and extent as in the case of the searabee, 



so that the remedial ineas'l IV- t . i be adopted Would be the 

 same in bot h c ISes. 



In the first place potatoes ought not to be planted on 



the same land for two successive crops, and next, all planting 



material should be ijuite free from infestation. This can bi 



assured by planting with slips grown in a nursery, from 



iininfested small routs or tubers 



The nursery should be established where there is the 

 least likelihood of the weevil being present, and should 

 be maintained long enough for it to become infested. Slips 

 for planting should never be taken from a field in which 

 either the sweet potato weevil or tin- searabee is known to be 

 present. It material for planting is scarce audit becomes 

 necessary to use slips {com a field which is suspected oi being 

 infested, none but the smallest tips ,,f the vines should be 

 taken forthe purpose, for the first attacks always occur in 

 the older more woody portions of the stem. 



the insect. The sweet potato weevil is a slender insect 



about J-inch in length. The head and wing covers are 



a bright, steely blue in colour, the thorax and legs being 

 reddish. The dead i- prolonged into a slender, forwardlj 



directed snout: the eyes are situated at the base of the SnOUt, 

 and the antenna c attached about midway its I. . 



This is well shown in the accompanying illustration, fig. 5, 

 which shows the adult, pupa and larva all enlarged to about 

 seven times their natural size. The larvae and pupae ue 

 whitish, the head of the former being yellowish brown, and 

 the eyes of the pupa reddish. 



The searabee is shorter ami stouter, being about 



! or ,' inch in length. Its snOUt is slender and turned undei 



the head in such a ivayas to render it quite inconspicuous. 



The attacks of these two insects produce the same 

 appearance in tin- potato. Planters and others who experi 

 ence anj trouble from insects attacking sweet potatoes would 

 do well to put an infested potato into a tight wooden box 



covered securelj with muslin or tine wire gauze, and real 

 a few insects in order to determine which species is causing 



the trouble. 



The sweet potato weevil is a serious pest, and every 



precaution should be taken to prevent its introduction into 

 any colon} where it does not exist at present. 



H.A.B. 



