*2 



THE AOTTCm-TU'RAL NF.^^P. 



VEHnuARV 9. 191S. 



INSECT NOTES. 



THE SWEET POTATO ROOT WEEVIL. 



Akhougii ibe above insect, which is known by the 



«cisntific name of Ct.'"- .'"""iVa) '»•«, bas not to far been 



recorded frcm the Lesser Antilles, it is well known as a pest 



■cf the sweet potato in -Tanviica. Cuba. Porto IWc-. British 



Gui&ca, acd ±e Bahamas. This insect also occurs in 



^eTeral other pans of the world, and is considered to be of 



c-ienal otieiE. It was first noticed in the United States 



about fortv^years ago near New Orleans, whence it has spread 



tr. tte other Gull S'.^acs atd to the We.^t Indies. This weevil 



i-quitedistinct fioin thesc«frabee cr Jacobs which is found 



attacking sneet | otatoes in some of the Lesser Antilles, 



but the datuage dote by the two weevils is similar, ard any 



measures taken to control the root weevil would also be 



applicable to the scarabee-' A somewhat detailed account 



ci' C'/las fotmir-trivs appeared in the .hn iruUtnol Ni"'S for 



April' 24." 1915 {\o\. XIV. No. 339), but in view of some 



recent investigations on this pest in Florida, ii nay be of 



iGterest to give a few additional notes on the subject. 



Some "cf the latest infnruiat'.on on thi« weevil, as it 

 occurs in the Gulf States, is given in tbe (,tuarterl;i Ihdhtin 

 of the State Plant Boar.: of Fh.udu, Vol. II, No. 1, by 

 Wilmon Newel), the Plant Commissioner, and it is from 

 this article that the following notes are mostly taken. 



jammrtt::!^^;:^ 



1 'i-m 



■si- ■-• 



»^ ■•> 



Kll.. 1. SWKE'I 



Am 11, I'l F'A. 



Potato Wkkmi 



ANJ> Lai:\ A. 



{Front U.S. Dept. Aijrii:.) 



utsi.KirnoN OK THE in^i-xt. The adult weevil is 



a .,i(:all ant-like insect about a {-inch long, with a smooth, 



tL:vi> body. The head is black, and i.s prolonged to 



form a teak, at llie en 1 of which are the biting mouth 



|)arti>. The tliora.x (or middle portion of the body) and the 



legs are a bright brick red, an<l the abdomen (or hinder pari 



of the b'xly) is a dark steel-blue. Although the adults 



posftss welidevelopecl wings they havt rarely been observed 



fljiog. 



i.iiK iiiMoiiv. The life history of this species has been 

 v/orked out under Te.\iis conditions by \. V. Conradi, 

 vitb iLe following results. The very small yellowish 

 ■wLiite eggs are laid in cavities made by the female 

 •ritter in the tubeis or in the vines, and a minute, foot 

 l^.c-.» gruii hatches in frcm five to six days. If the egg is 

 h.'.c en tl:e stem (he emerging grub may sometimes 

 I :,'v u;ivl in the stem and complete its developnicnt 



there, but more often it works its way down the inside- 

 of the stem t^ the tuber. Grubs hatching from eggs laid 

 in or on the tuber itself bore into the tuber, and complete 

 their development in about fifteen days, very (juickly riddling 

 the tuber with numerous tunnels which become tilled with 

 excrement and decaying matter. When full grown the grub 

 changes into a pupa, and the adult weevil emerges in about 

 eight days. The whole development of the insect occupies 

 froiii twenty eight to twenty nine days, and allowing a few 

 days between tlie maturing of the adult and the laying of the 

 first ejigs, it will be seen ihat a complete generation can be 

 prc'duced in about thirty-five days. Since tLe weevil breeds 

 continuously in the tropics, there is a possibility of ten or 

 even eleven broods a year. It was found that the egg- 

 laying period may continue for twenty-one days, so that 

 there are no distinct generations, but weevils in all 

 stages of development may be found almost any time. It 

 will thus be seenthat in the tropics this insect, with its 

 powers of continuous reproduction and development, may 

 be extremely destructive. 



K00ii-i'l>ANTs. The sweet potato {I/^oiin-a bal.ifus) and 

 the morning glory {/poii<ra sp. ) arc the favourite host 

 plants, and the weevil eggs and liirvae have been found on 

 closely related vines. The adults, however, can feed upon 

 a great variety of vegetation. 



now lilt: wKEViL sPRKADs, The adult insect has only 

 once or twice been observed in (iivht, and its slow rate of 

 spread in a newly infested area shows that spreading by Hight 

 need hardly be fciken into account. This pest is dissem- 

 inated mainly by the movement of infested sweet potatoes 

 and. sweet potato plants from one locality to another. 



x..\Ti.i:Ar. coNTRoi.. The sweet potato root weevil i.s 

 remarkably free from natural enemies. No pamsites have 

 been recorded, and there is no mention in any records of 

 birds destroying the wi evils. Therefore reliance must be 

 placed on arlificlal methods to control this pest. 



AETiKK lAi. ((iNTr.oi.. TIlis includcs i (iiarantinc intasures 

 to prevent the spread of the weevil to new areas, and direct 

 methods to reduce damage in areas already infested. 



A short outline of the i[uar;intine measures adopted by 

 the Plant Hoard of Florida to exclude the sweet potato 

 root weevil was given in the Aciricultural Nins for November 

 .S, 1917 (Vol. .WI, No. 40.")). These measures prohibit the 

 importation of any part of the sweet potato and morning 

 glory plants into Florida from outside, and also prevent the 

 shipping of auy portion of these host plants from the infested 

 areas in Florida, and the movement tif any sweet potato 

 tubers from 1 lie infested areas, unless first fumigated by an 

 agent of the Plant Board, and certified by him. 



M'.MicA'i lox. Experiments made by Conradi have 

 shown that all stages of thin weevil can be killed by fumi- 

 gating the tubers. Carbon bisuljjhide is used at the rate 

 of 3 lb. to each I 000 cubic feet of space, and it is essential 

 that the compartment used for fumigation be air-tight. 



i;iii)U('Tio,Ndi' DAMvoK. It is lecognized that once the 

 weevil has become well established in a district there is no 

 .satisfactory way of eliminating it, but nuirli can be done to 

 reduce the damage. 



The following are some of the control measures which 

 have proved to be of practical value in the Gulf States, and 

 arc also apitlieable to West Indian er.nditions. No one 

 measure alone will have much efl'cct in reducing the weevils, 

 but a combinati'ii of allot thcin, if used thoroughly -.ind 

 .systematically, will bring about a marked reduction in the 

 numbers of the weevils and the extent of their damage. 

 These methods can also In- nsed with good n'sults against the 

 scarabee or Jacobs; — 



