162 



THE AGRICULTUEAL NEWS. 



May 30, 1908. 



■various shield scales (/ycrrt/iiii??! spp.), the glassy star 

 scale (Vinsonia stelUfrrd), the orange mussel scale 

 ■{Myiilaspiscitricola), the mealy shield scale {Priifapul' 

 vinaria pyrifurmlH), and the black line scale 

 (Isehnaspisfi.liforinis). In addition there are n grear, 

 number of scale insects occurring on various trees and 

 plants in the West Indies, some of which have probably 

 not yet been identified. 



It is evident that any measures designed to 

 prevent or control the spread of black blight musD l)c 

 directed against the scale insects. These pesr.s are 

 well known in most parts of the world, and the total 

 loss caused by their depredations on fruit and vegetable 

 crops reaches an pnoiinous figure annually. Broadly 

 speaking, there are three recognized methods of keep- 

 ing scale insects in check, and these have been adopted 

 with more or less success in different countries. 



The first method consists in encouraging, and if 

 ■necessar}', introducing new species of the natural insect 

 enemies of tjie scales, of which there are many, both 

 predaceous and parasitic. Chief among the former are 

 ^various species of lady-bi ids, while the larvae of the lace- 

 Avinged flies (Chri/sopa spp.) also do good service in 

 this direction. The parasitic eneinies of the scales are 

 chiefly minute hymenopterous insects. The presence 

 of these latter is not always easy to recognize, but if on 

 ■examination, the common black scale is found to be 

 pierced with a minute round hole, it is a safe indica- 

 tion that parasitization has taken ))lace. At least three 

 species of scale insects occur in Grenada, which are also 

 prevalent in California, and which, in the latter I'oiintrv, 

 are parasitized by the hymenopterous insect ,Si-ut<-llisl(i 

 ■cyanc.a. Reports from California state that the intro- 

 •duction of <S'. r;yr(;/r(( from South Africa for parasitiza- 

 tion purposes has been attended with a very giatifying 

 .measure of success. Attempts are being made to 

 introduce this valuable insect into Barbados, and if 

 these efforts are successful there should be a sufficient 

 number available in a short time for introduction into 

 the other islands. Where the natural insect enemies 

 ■<Io not exist locally, however, their introduction and 

 acclimatization is necessarily a protracted and expensive 

 business. If the ni'cessary funds were available, in 

 course of years reasonable hopes might be entertained 

 as to the ultimate development of this in<'ans of 

 ■controlling the scales. 



A second method for keeping the scale insects in 

 check consists in spraying them with some insecticide. 

 This forms the best method of direct attack in the 

 "West Indies, and one which should be employed when- 



ever practicable, and where the cost of the operation is 

 not prohibitory. . Details as regards the composition 

 and use of mixtures that have been found usefid for 

 sprnying purposes by officers of the Imperial Depart- 

 ment tif Agriculture, will bo found in ramphlet No. 7 

 of the Series issued by the Imperial Depaitment, 

 entitled 'Scale Insects of the Lesser Antilles" 

 (Part I), where also the chief scale insects preva- 

 lent in the West Indies are described and figured. 

 A knap-sack sprayer will usually be found most 

 convenient for ordinary estate purposes, more especially 

 in cases where the ground is rough and uneven. Fur 

 ti-ees of 20 to 30 I'eet high, however, a sprayer such as 

 the •■ Fruitall ' tyjje will be necessary. Trees should be 

 pruned befoi'C spraying and all useless branches lopped 

 <jff. By this means there will be a better chance of 

 the liquid reaching all paits of th(.' trees. In dealing 

 with large trees badly affected it has been recoui- 

 mended that they should be lopped as closely as 

 possible, and the cuts tarred ovei-, the whole being 

 afterwards thoroughly coated with a good lime wash. 

 In conne.xion with spraying, it is important to remem- 

 ber that clean cultivation is necessary, and all useless 

 trees and plants near by that are infested with black 

 blight sho\dd bi> cut down and liurned, since the pe&t 

 is likely to spiead from such vegetation to cultivated 

 trees. 



In an island so badly infested with black blight as 

 is the cnse at Grenada, it is practically impossible 

 completely to exterminate the scale insects without the 

 expenditure of a sum of money which is not at present 

 warranted by the actual amount of damage caused by 

 these jiests. lender the circumstances, it is all the more 

 ineund)ent upon ij-idividual planters to keep the blight 

 in check on their own estates by care in the exercise 

 iif clean cultivation, and by the use of insecticides 

 w herever spraying is practicable. 



In cases where trees growing along road sides or 

 on waste lands which are not under j)roper control are 

 affected with black blight, the (jovernmeiit should 

 under take thediity of looking after and controlling the 

 pest, and thecost of doing so should be met from public 

 funds. The first operations should always be started 

 to windwardof the infested areas, in order to prevent 

 the spread of scale insects to trees already treated. 



In California, the method of fumigating affected 

 trees, over which a moveable tent has first been erected, 

 has been adopteij with considerable success by many 

 orange growers. This lievice, however, is probably not 

 suitable for general adoption in the West Indies. 



