218 



THE AGRICULTURAL NEWS 



July 13, 191S. 



INSECT NOTES. 



STARCH, INSTEAD OF LIME, WITH 



ARSENICALS. 



In tlie Agricultural yewi tor November 6, 191J 

 (Vol. \IV, No. 353) the attention of readers was drawn to a 

 cheap and efficient method for poisoning certain caterpillars 

 which are pests of staple crops in St. Vincent. This nieilmd 

 was devised by Mr. S. C. Harland, Assistant Agricultural 

 Superintendent of St. ^"incent, in the course of liis experiments 

 to control the corn ear worm {l.apliygma fnig^iperda). Sum- 

 maries of the information contained in the above article 

 appeared in the St. Vincent Annual Report for 1915-16, and 

 in the Review of Applied E>it(»no!o:^\ Vol. IV, p. 42. 



It has been thought desirable ',o remind planters of the 

 value of this poison mixture, es]iecially in view of some 

 recent experiments in the control cif the corn worm carried 

 out by the Superintendent of Agriculture in St. Lucia, which 

 •will be referred to below. 



Harland found that by diluting Paris green or arsenate 

 of lead with a low grade arrowroot starch which had been 

 passed through a sieve of eighty meshes to the inch, a mix- 

 ture was obtained which seemed to have a peculiarly deadly 

 effect upon all kinds of caterpillars. He continues; 'The 

 greater effectiveness of the.se mixtures, as compared with 

 similar lime mixtures, is thought to be due to the fa'jt that 

 insects usually avoid vegetation where lime is present, and 

 refrain from eating it until actually forced by hunger. A 

 longer period of time thus elapses before the poison is taken 

 in than in the case of starch mixtures, where feeding goes on 

 at the same rate as before Greater dilution is thus possible 

 with starch mixtures, and the cost of applying poison becomes 

 proportionately less.' Harland states that the additional 

 advantages of .starch over lime are that (a) starch adheres 

 better to leaves than lime, (b) it is insoluble in water, (c) it 

 is more pleasant to sitt. 



In the course of his ob.servations on the habits of 

 Laphygma in St. Vincent, Harland found that the larvae 

 after hatching from egg clusters on tlie leaves, remain 

 ijuiescent for a time and then migrate to the heart of the 

 young plant where they begin feeding immediately, it was 

 observed that the young larvae showed such a marked 

 tendency to devour each other that it was rarely possible to 

 find more than two full-grown larvae in a single plant. 

 tSimilar cannibalistic tendencies in this species have been 

 observed by JJodkin in British Guiana (/oitnial of the Board 

 of Agrieiiltiire of British Guiana, Vo'. VI, No. 4, p. 172). 



Since the larvae of the corn car worm, or corn worm as 

 it is often called in these islands, remain in the heart 

 of the plant, they are not ea.sy to reach by the ordinary 

 method.s of dusting or spraying, and both these methods 

 are wasteful of materials. It has been found that the 

 .simplest and most economical method is to drop a small 

 (juantity of poison into the heart of each plant, using an 

 ordinary pen nib. (Harland /'?<. cit.) 



Experiments with various mixtures showed that both 

 Paris green and lime separately and together burn the leaves 

 of corn, .so that they cannot be used against the corn worm. 

 Har]ait.d found that the best poison for the control of 

 Liiphys^ma fnif^iperda on young cnrn is a mixture of lead 

 arsenate and starch in the proportion of 1 : :!0 by volume. 

 Paris green and starch may be used against rater[)illars on 

 most other cro]js at the rate of 1 : 60 by volume. 



In this connexion a communication has lately been 

 received at this Office from .Mr. .\. J. I'rooks, Superintendent 



of Agri'ulture, St. Lucia, in which he gives an account of 

 some experiments which he has been making to control the 

 corn worm. 



The 1 : 30 lead arsenate and starch mixture was used in 

 the manner recommended by Harland. except that the starch 

 was passed through a sieve of sitty meshes to the inch 

 instead of eighty. 



I'rooks has given the following description of his experi- 

 ments; The mixture (mentioned above) was applied by 

 means of an ordinary pen nib. •.he point being pushed into 

 the S'lft stem of a piece of bamboo grass, oi similar materia], 

 to form a handle. The curved base ol the pen holds a suffi- 

 cient amount of the poisonous mixture required to be dropped 

 into the lieart of each corn seedling. 



'From extensive trials made by this Department 

 (St. J^ucia) this mixture has given by far the best results of 

 any ever suggested for dealing with this troublesome pest, 

 which is almost entirt-;y responsible for the lack of interest 

 taken in corn growing locally. 



'The processes of dusting by the use of muslin bags or 

 machines formerly employed have always been a failure, 

 the machines getting out of order and the bags tearing or 

 becoming choki d through the mixture getting damp. 

 Too much or too little was applied and the results were ar 

 the best doubtful. 



'I'aris green, lime, and such mixtures have never proved 

 satisfactory on corn owing to their burning properties, ani 

 in some instances greater injury has been caused by the 

 application of these remedies than by the worms themselves.' 



P.rooks then goes on to say that the adulterants usually 

 sugge.sted, such as corn meal, etc., are often unobtainable, 

 but that corn is a crop suited to all soils where cassava or 

 arrowroot is regularly grown, so that there should be no dirti- 

 culty in obtaining a good stock of starch as an adulterant. 

 He suggests that the outer layer of the starch blocks, which 

 is often dirty and unsaleable, could be u.sed instead of the 

 higher grade. 



Prooks continues; 'The only apparatus needed is a cit;a- 

 rette tin to hold the mixture and a pen nib to apply it. The 

 planter is not left in doubt as to the results, as the worms 

 leave the heart of the seedling when the poison they have 

 consumed begins to worry them, and they are found stretched 

 out flat and dead on the upper surface of the broad sheaths 

 of the leaves. Our experience has shown that when- the 

 mixture is applied just before sunset the worms are ijuite 

 dead by the following morning. 



'A careful test was made by the individual inspection of 

 each seedling in a half acre plot, and although the infesta- 

 tion had been great, due to the late arrival of the lead arsen- 

 ate, not a single live worm was found after a period of four- 

 teen hours from the time of applying the poison. During 

 this period lieavy storms were experienced and a rainfall of 

 ■82 inch was registered. Py following the simple instruc- 

 tions given in the memorandum from St. Vincent absolute 

 succe.ss is a.ssured even in spite of unfavourable weather 

 conditions.' 



Brooks considers it exceedingly lielj)fiil to find such an 

 effective, practical, cheap and easy method of dealing with 

 a pest, and is of the opinion that much more corn could be 

 and would be grown, if peasants and others knew ot such 

 a simple remedy for the greatest trouble they meet in the 

 cultivation fif corn. 



It would appear then from the above experiments in 

 St. Vincent and St. Lucia that a mixture of lead arsenate' or 

 I'aris green with starch jirovides a remedy that is both chcau 

 and efficient, in that only one a])i)lication is necessary, if 



