362 



THE AGRICULTURAL NEWS. 



Novembeb 6, 1915. 



INSECT NOTES. 



STARCH, INSTEAD OF LIME, WITH 



PARIS GREEN. 



The attention of planters in St. Vincenl hasbeen 

 directed bj Mr. W. X. Sands, the Agricultural 

 Superintendent, bo the following description of new 

 methods devised, and the resiilts of investigations and 

 experiments made, by the Agricultural Department 

 at the Experimeni Station and on estates, which have 

 led to the discover) of cheap and efficient means of 

 destroying certain 'worms' attacking staple crops in 

 St. Vino 



Mr. S. < '. Harland, B.Sc, the Assistant Agricul- 

 tural' Superintendent, who has had charge of the 

 work during the past four months, has written the 

 following important memorandum, containing results 

 which may have a wide application in tropical 

 culture: — 



In .May ot this year it became important, in view of the 

 proposed extension of Indian corn cultivation in the Colony, 



to devise methods of controlling tin. rn worm (Laphygma 



trugiperda). While working on this subject it was discovered 

 that, if the arsenical poisons, Paris green and lead arsenate, 

 ■were diluted with low grade arrowroot starch which had been 

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

 ture was formed which seemed to have a peculiarly 

 deadly effect upon all kinds of caterpillars. The greater 

 effectiveness of these mixtures, as compared with similar 

 mixtures, is thought to be due to the fact 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 bi I'm 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 possi- 

 ble with starch mixtures, and the cost of applying poison 

 becomes proportionately less. Additional advantages are — ■ 

 (a) starch adheres better to leaves than lime, (b) .it is 

 insoluble in water, -(c) it is more pleasant to sift. 

 i ONTROL OF THE CORN w ORM. 



The corn worm (^Laphygma frugiperda), known in 

 British Guiana as the 'rice worm' and in the Southern 

 States of America as the 'fall army worm,' as the most, 

 important pest of com in St. Vincent. The life-history has 



been worked out at the Experiment Station, and this lias 



ted greatly in the work of devising means of control. 

 The following points in the life-history are important: — 



(1) Thi - . fifty to 350 in number, are laid usuallj on 

 the back of the leaf, in a cluster. They are easily seen, and 

 thus our ot the best ways of combating the pest is to collect 



ggs In fore they hatch. At present, however, 300 

 cluster I per day are being, collected at the Experiment 

 acre of corn, so that the cosl of hand 

 collecting over a large area would b< me a serious item. 



(2) The young larvae remain quiescent for a time after 

 hatching and then migrate to the heart of the young plant, 

 where they immediately begin to eat. fortunately they 

 liave cannibalistic tendencies, and prey upon each other to 

 ju.cn an extent thai it is rare to find more than two full- 

 grown larvae in asingle [plant. 



(:!) This habil of remaining in the heart of the plant is 



made use of, iii that it is necessary to put poison in this 



particular place only. Applying the poison with ordinary 



; apparatus is not economical. The practi lowed 



at the Experiment Station is to drop a small quantitj 

 poison into the heart of each plant, using an ordinary' pen 

 nib. 



ttl VLS « I I'll v IRIOUS POISONS. 



The following combinations have been used in the 

 experiments, and short notes on each arc appended. Tin- 

 proportions are by volume: — 



Lime. Burns the leaves severely, but seems to destroy 

 the worms if it comes in contact with them. 



Linn and Paris green (1:6) Worms destroyed but 

 leaves severely damaged. 



Linn and Pat is green (1:20) ditto. 



Lime and Paris green (1:60) 



Starch and Pans green (1:6). As above but icted 

 more rapidly. 



Stmck and Pans green (1:20). Worms dead within 

 twenty-four h»urs and the damage to the leaves is consid- 

 erably less than with the 1:6 mixt 



Start* and Paris' green (1:100). Worms .lead within 

 forty-eight hours. Damage to leases is still apparent, but 

 the plants quickly recover. 



Starch and lead arsenate (1:20). Worms dead in 

 twenty four hours. Damage to leaves -light. 



Starch and /<ad arsenate (1:30). Worms dead in 

 twenty four hours. Damage to Leaves negligible. 



As both Paris green and lime separately and together 

 burn the leases of corn severely, they cannot be used against 

 the corn worm. 



A mixture of lead arsenate and starch in the proportion 

 of 1 part of the former to 30 parts of the Utter is recommend 

 for the control of the corn worm on young corn. 



The 1:100 mixture of Paris green and si trch can be 

 used on half-grown plant-. 



It will be seen that a cheap and efficient method of 

 combating the u worm has been discovered.. 



THE T VI.I. \l:.M\. W o|;\|' |\ jJJ or i \. 



In the months of June and July grea was done 



to crops in Bequia by the 'fall armj worm' or i variety of 

 it. The pest did not confine itself to com Inn ittacked most 



growing crops. A 1:6 ixture ol Paris green rad starch 



was used with great success. 



THE IRROWROOT WORM (< 'alpodes ethl 



At certain times of the year in St. Vincent, arrowroot 

 fields are attacked by the arrowroot worm i completely 



defoliated. Opinions among planters diffei aether any 



great difference is shown between the produce of attac] 

 and unattacked cultivations. One would imagine that as 

 the starch is elaborated in the lea to the latter 



would result in a corresponding reduction of the quantity of 

 starch stored in the root. This question w settled by 



experiment as s i as practicable. 



.Meanwhile it is useful to know that tie Troo1 worm 



can be destroyed by the 1:60 Pa A mixture. 



Three hours after the poison was applied to a plo [ arrowroot 

 it was evident that some of the larvae were d\ g. [n less 



than twelve homs. 90 per cent, of them were dead. One 

 applical en only was necessarj . 



THE OROt \l> NUT WORM I uiiideul ili. d 



At Ratho Mill estate ground nuts wen ly attacked 



bj 'he larvae ..; an unidentified g< let i id moth, and consider- 

 able areas were completely defoliated \ll ' Mi,,. 



1 :60 Paris green mil starch e a1 tack in 



two d 



