318 



[October, 1909. 



PLANT SANITATION. 



INSECTS ASSOCIATED WITH THE 

 COTTON PLANT IN CEYLON- 



By E. Ernest Green, 

 Government Entomologist. 



The insect enemies of the cotton plant 

 in Ceylon have hitherto x'eceived little 

 notice, owing to the merely spasmodic 

 attempts that have been undertaken to 

 cultivate this plant until the last few 

 years. The recent demand for British- 

 grown cotton has, however, drawn fresh 

 attention to the possibilities of cotton as 

 a profitable industry in the drier parts 

 of the Island. Even now the area under 

 cultivation with this product is limited 

 to a few hundred acres. But our very 

 short and limited expeiience has been 

 sufficient to show us that the cotton 

 plant is remarkably subject to insect 

 enemies of many kinds, and that — if the 

 industry is to be a success — we must be 

 prepared to fight these enemies from the 

 very commencement. 



The rapidity with which this plant be- 

 comes infested by its particular enemies 

 is most remarkable. A small plot was 

 opened on the Peradeniya Experiment 

 Station in the present year for the first 

 time. As far as I can learn, no cotton had 

 previously been grown in the neighbour- 

 hood. But the very first crop raised 

 was so badly infested by boll-worms and 

 cotton-stainers as to be practically value- 

 less. One of these boll- worms (Gelechia 

 gossypiella) is not known to breed in 

 any other plant, and is consequently de- 

 pendent upon the cotton for its exis- 

 tence ; the other pests frequent allied 

 plants, but are seldom found in such 

 abundance as on the cotton. 



We have, fortunately, no such alarm- 

 ing pests as are prevalent in the 

 American States, where the notorious 

 'Boll-weevil' alone has been engaging 

 the attention and taxing the energies 

 of the economic entomologists of the 

 United States for more than ten 

 years. To give some small idea of the 

 importance of this pest, I will quote 

 from a recent circular of the U. S. 

 Department of Agriculture, which states 

 that " a conservative estimate shows 

 that since the weevil invaded this coun- 

 try it has caused a loss of 2,550,000 bales of 

 cotton, at a value of about $ 125,000,000," 

 —a sum equivalent to twenty-five million 

 pounds sterling. 



But our comparative immunity from 

 such overwhelming enemies is rather 

 apparent than real. It we had the same 



acreage under cultivation as there is in 

 America, and if the greater part of that 

 acreage was as badly attacked by our 

 local boll- worm as was the half-acre plot 

 on our Experiment Station, the total loss 

 might rival, or even exceed, the figures 

 just quoted. Then, with the gradual 

 extension of the area under any pro- 

 duct, it is the usual experience that fresh 

 pests will come into prominence, attract- 

 ed by a constant and unfailing supply 

 of food. 



However, the consideration of such 

 figures must not be taken too seriously. 

 An immense incalculable loss is always 

 taking place, with every product, 

 through the depredations of various 

 pests ; and yet enough remains to re- 

 pay the cultivator. It has been esti- 

 mated that, if every sparrow in England 

 consumed one farthing's worth of corn 

 during the year, the annual loss through- 

 out the British Islands would amountr to 

 over a million pounds. We might thus 

 pile up a stupendous total of loss to the 

 British farmers during the last century. 

 But corn is still grown and will continue 

 to be grown with profit. In the same 

 way, if the annual loss of leaf through 

 our various tea pests — shot-hole borer, 

 helopeltis, tea-mites, and sundry cater- 

 pillars—could be put into figures, -it 

 wouldjprobably scare a considerable num- 

 ber of worthy people at home, whose 

 capital is invested in this product. 



It will be sufficient to realize that the 

 cultivation of cotton will not be merely 

 a matter of putting in the seed and har- 

 vesting the crop in due course; that 

 there will be numerous enemies to be 

 contended against ; and that careful at- 

 tention will be necessary at all stages of 

 the plant. , 



In the time at my disposal, it will be 

 impossible to offer a treatise upon the 

 particular treatment of all these enemies, 

 out, to assist in the recognition of them, 

 I have enumerated and briefly described 

 some of the principal insects associated 

 with the cotton plant that have come 

 under my observation. 



The most important of these are the 

 boll-worms, of which we have two 

 species in Ceylon. 



1. The ' Pink Boll-worm ' (Gelechia 

 gossypiella) is a small coral-pink maggot- 

 like caterpillar that feeds among the 

 ripening seeds of the pod. The eggs are 

 laid singly on the leaf -like bracts at the 

 base of the boll, and the young cater- 

 pillar bores its way into the pod. This 

 tunnel is apparently enlarged and kept 



