282 



THE AGRICULTURAL NEWS. 



Septkmber 9, 1905. 



INSECT NOTES. 



Insect Pests in Porto Rico. 



The Annual Iteport ot the I'orto Itiuu Agricultunil 

 Experiment Station for 1903-4, recently issued, contains 

 a chapter on insect pests in which the iirinciiial insects of the 

 year are briefly reviewed. 



It is interesting to note that no complaint was received 

 lit damage done by the changa or mole cricket during the 

 year. The bait of grass and Paris green, the use of which 

 was described in the Ayiriridtural News (Vol. II, p. 200), is 

 l)eing used with good results, and the freedom from injury 

 from the mole cricket is attrilmted to the general use of this 

 bait. 



The Ijud maggot {Lonchani chah/bea) of the cassava has 

 continued a serious pest. This is a small tly, the larvae of 

 which live in the terminal buds of the cassa-\-a stems. Hand- 

 picking of the infested portions has been found the best 

 remedy, though the application of tobacco dust has at times 

 given good results. 



The cotJ'ee leaf-miner has long been known as a serious 

 piest of coffee. It is estimated to cause a loss of 8150,000 to 

 ■'?300,000 in one year in Porto Itico. liecently, howevei-, 

 this pest has been on the decrease in several districts of the 

 island, due largely to the attack of a small Hymenopterous 

 jmrasite {Chri/socharh Uvidus) which destroys the larvae of 

 the leaf-miner. This parasite was first named from 

 a specimen collected in St. Vincent, but its habits were not 

 known until recently. It is hoped that this parasite will 

 continue to increase in nundiers and further reduce the 

 damage by the leaf-miner. 



Application of Paris Green. 



The rapid development of the cotton industry in the 

 West Indies during the past few years has been followed by 

 an equally rapid development of the cotton worm. 



In order to grow cotton successfully, it is now generally 

 admitted that it is necessary to use some insecticide for 

 controlling this pest. Of all the insecticides on the market 

 Paris green is the best known and most extensively used 

 in the West Indies. Other insecticides arc London purple 

 and lead arsenate. Paris green and London purple are sold 

 as dry powders and may be applied to plants as a dust or 

 in water as a spray, while lead arsenate is sold in the form 

 uf a wet paste and can be a[iplied oidy as a spray. 



In the cotton-growing districts of the United States, 

 extensive exjieriments have been carried on in the use of 

 insecticides and with a great variety of machines for their 

 application. 



Spraying machines from the simplest form of bucket 

 sprayer, which is carried about and operated by one man, 

 to the elaborate sprayer, drawn b}' a pair of horses and fitted 

 to spray sixteen rows of cotton at one time, have been tried, 

 as well as a great variety of dusters, sifters, powder guns, 

 bellows, etc. 



Many of these have been ingenious devices invented 

 expressly for use in the cotton fields, and yet with all these 

 available the common practice is that of sifting the poison 



through cloth in such a way that it falls as a fine dust on the 

 plants. This method, which has already been described in the 

 U'tfl Indian Ihdhtin (Vol. IV, jip. 271 and 310), is briefly 

 this : A bar of wood about 5 feet long has at each end a small 

 bag of osnaburg which carries the poison. A boy mounted on 

 a mule carries this in front of him in such a way that the bags 

 hang above the cotton rows. A gentle tai)ping of the bar with 

 a small stick causes the poison to sift out over the plants. 

 In the Sea Islands a shorter bar is used with a bag at 

 one end. In this case the labourer is not mounted, and 

 the bar is used merely to enable him to get the bag of 

 poison above the topmost leaves of the [ilant. In the 

 West Indies the most common practice is to use a bag of 

 ' ticklingburg ' for sifting the mixture of Paris green and lime 

 over the plants. On some estates the bag is used attached 

 to a short stick, but on others the bag is held in the hand and 

 the poison is sifted from the bag by shaking it over the plant. 



Powder guns and spraying machines are also in use to 

 some extent and are said to give satisfactory results. 



The powder gun is a machine for applying pciisons in 

 a diy condition. It consists of a receptacle for holding the 

 poison, a revolving fan for blowing it out, and a long tube 

 to give direction to the blast of air carrying the poison. The 

 machine is carried and operated by one man, and it is 

 claimed that its initial cost is justified by the greater amount 

 of work done by one man and by the great saving in the 

 amount of Paris green used. While there is no doubt that 

 a great saving could be effected on certain estates in the 

 amount of Paris green used in dusting with the bag, it will 

 generally be found that such estates are using far more than 

 is needed, that is, the labourers are wasting it. In such cases 

 it might be found that the use of the powcler gun would stop 

 this waste. 



In the first place, instead of having bags made of proper 

 material and of a convenient size, some estates use an 

 ordinary sacking, such as oat sacks, bran sacks, etc., which 

 are of too coarse a texture, and, in addition, are too bulky 

 and cumbersome. 



One estate in Uarbados found by careful calculation 

 that last season the cost of each treatment was about 2s. 

 per acre of cotton. This included Paris green, lime, and the 

 labour of applying. The poison was used at the rate of 1 tt). 

 to 6 Jj. of lime and this gave e.xcelleut results. The 

 amount of Paris green used per acre was a little over I lb. 

 The same treatment this season is giving as good results 

 up to the present time. In other cases, however, as much 

 as 5 or 6 Bb. of Paris green have been used per acre for 

 a single application; the use of such a large amount would 

 indicate that the poi.son is being wasted. In other cases, 

 again, it is said that, although plenty of Paris green has been 

 used, the worms have not been killed. This has probably 

 been the result of delaying the application too long. There 

 are still in Barbados estates where great numbers of worms 

 are allowed to become nearly full-grown before they are 

 noticed and it is then too late to stoi> their ravages. 



For the successful treatment of this pest it is necessary 

 that a sharp lookout be kept and that steps be taken at once 

 to check it by prompt application of poison. An excessive 

 amount of poison can do no good, only a certain amount falls 

 on the leaves and the rest is wasted. 



If rains wash off the poison another application must be 

 nuide. Cotton growers, who keep a careful lookout for the 

 first and all subsequent appearances of the worm and who 

 see to it that the poison su[i[ilied to the labourers is properly 

 used and not wasted, will find that the worm can be 

 controlled, and that without great expense. 



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