346 



THE AGRICTJLTUEAL NEWS. 



NONEMBEE 3, 1917. 



INSECT NOTES. 



THE PINK BOLL WORM. 



(Pectinophora [Gelechia] gossypie/la, Saunders.) 



This insect has more than once been the subject of 

 articles acd brief notes in the pages of the Agricultural 

 Neivs, the more recent references being those of April 21 

 and May 19, 1917, where mention was made of the discovery 

 of this pest in Mexico and Brazil, respectively. Since the 

 appearance of the later of these two notices a bulletin of 

 considerable importance has been published by the United 

 States Department of Agriculture giving the latest infor- 

 mation on the life-history and habits of this pest. It has 

 seemed advisable, therefore, in the first place to bring the 

 more important points contained in this article to the atten- 

 tion of readers of the Ai/ricultural Neivs, and secondly, 

 to refer briefly to the measures which have recently been 

 taken in the British West Indies to guard against the intro- 

 duction of the pink boll worm into these islands. 



Since 191.5 this insect has formed the subject of a 

 detailed study in the Hawaiian Islands where the cultivation 

 of cotton has practically been abandoned owing to its 

 ravages. These investigations have been carried on in 

 Hawaii mainly by Mr. August Busck, of the United States 

 Bureau of Entomology, and the results have recently been 

 published in the Journal of Aaricultural Researv/i, Vol. IX, 

 Ko. 10. 



The pink boll worm was first desciibed from India, but 

 later evidence points to Africa as being the original home of 

 this insect. It has spread to most, if not all, of the cotion- 

 prowing districts of Africa, A.sia, Japan, Ceylon, Straits 

 Settlements, Philippines, and Hawaiian Islands, and has 

 within the last few years become established in Brazil and 

 Mexico. It is now considered to rank among the half-dozen 

 most important insect pestb of the world. Some examples 

 showing the extent of its damage within recent years may 

 be of interest. It was stated in 1916 that in Egypt the 

 pink boll worm often reduces the yield of lint 50 per cent, 

 or more, and materially lessens the amount of oil 

 obtained from the seeds. A recent report by Gough of the 

 damage caused by this pest states that it now occurs where- 

 ever cotton is grown in Egypt; in the last week of October 

 1916, 87 per cent, of the green bolls in Lower, 78 per cent, 

 in Middle, and 60 per cent, in I'pper Egypt were attacked by 

 It. Maxwell-Lefroy estimated in 1911 that the minimum 

 loss in India from the insect is more than £2,000,000 

 annually. 



In the Hawaiian Islands during 1915 the boll worm 

 infested from 50 to 99 per cent, of the bolls in the few fields 

 of cotton still being grown, and destroyed from one-half to 

 nine-tenths of the lint. The introduction of the pink boll 

 worm into Brazil was referred to in a brief note in the 

 Agricultural A''«("s of May 19, 1917, in which it was stated 

 that up to 1914 this insect was not found to be present in 

 Brazil, but that towards the end of 1916 another survey of 

 the cotton districts showed that the pest had become 

 thoroughly established. Recent reports show that last year 

 the pink boll worm caused a loss of 50 per cent, of the cotton 

 crop in some localities. It is now recognized that this insect 

 will continue to take its toll of the cotton industry in Brazil, 

 as it is doing in other infested countries, in spite of any 

 measures which may be *aken to control it. 



LIFE-HISTORY. 



The small eggs are laid singly or in small groups on 

 any part of the green cotton boll or its calyx, or even in the 



flower, but are by far most commonly found near the apex of 

 the green boll in the slight longitudinal depressions which 

 indicate its divisions. Dissections showed that a single 

 moth is capable of laying more than 100 eggs. These hatch 

 in from four to twelve days after they are laid. 



The young larva is nearly pure white, and it is only in 

 the fourth and last instar that it assumes the pink colour 

 that has given it the popular name of pink boll worm. 

 A detailed account of the feeding habits of the larva is given 

 by Mr Busck, and some of the main points are of interest. 

 The newly hatched larva bores into the boll under or near 

 the egg-shell, and its subsequent-progress seems to depend 

 partly upon the position of the egg and the condition of the 

 boll, and partly upon the direction the larva may happen to 

 choose. It usually bores in near the apex of the boll, and 

 tunnels down through the soft inner walls to the base 

 of the boll before it attacks one of the lowest seeds. 

 Then it gradually works its way upward again, feeding 

 on the seeds as it goes, and finally ends as a mature larva 

 in one of the seeds nearest the tip of the boll. The larva 

 feeds exclusively within the cotton boll, and does not 

 attack the leaves or shoots. It usually confines its attacks 

 to a single section of the boll, but may wander into adjoin- 

 ing sections. When, as is often the case, two, three, or 

 more larvae infest a single boll, the value of the seeds and 

 lint is entirely destroyed. 



The larval stage occupies from twenty to thirty days 

 during the summer in Hawaii, but this period may be much 

 prolonged in colder weather, or under abnormally dry 

 conditions. In temperate climates the insect passes the 

 winter as a larva within the seeds. 



The pupa is usually formed within the boll, partly 

 inside the last seed attacked by the larva. Before com- 

 pleting the cocoon, which consists of a single, thin, but 

 rather tough, layer of dirty-brown silk, the larva eats a round 

 hole through the outer wall of the boll to insure the escape 

 of the issuing moth. The pupal period lasts from ten to 

 twenty days. 



The moth is small, dark-brown, inconspicuous, and 

 sluggish. It is rarely seen in nature, .since it hides during 

 the day on or near the ground, and sometimes even burrows 

 into the surface of the soil. Egg-laying usually begins soon 

 after emergence, and the moths die shortly after oviposition. 

 The entire life-cycle may under favourable conditions be 

 completed in thirty five days, but about fifty days seems to 

 be the more usual period. 



HABITS OF THE MOTH. 



The secretive habits of the moth were well shown by a 

 number of experiments made both in the field and under 

 artificial conditions indoors. In the outdoor experiments 

 several dozen moths of this species were repeatedly liberated 

 in the middle of a cotton field, by shaking them out of a jar 

 on to the ground. Within a minute none were in sight; 

 all had effectively hidden away on the uneven surface of the 

 ground. Under indoor conditions hundreds of moths were 

 liberated weekly, but rarely were any to be found during the 

 day-time. 



This moth .shows an aversion to light of any kind 

 whether it be sunlight, difi'used daylight, or artificial light. 

 I>uring the day it hides in obscure places, and only becomes 

 active at dusk. Experiments have been made to try 

 and attract this moth to traplight.s, but without success. 

 'Strong kerosene and acetylene lamps, placed in a raoat eflfect- 

 ive manner with white sheets as backgrounds, on a porch 

 and in the windows of a cottage surrounded within 20 feet 

 by heavily infested cotton fields, failed to atti\ct a single 

 individual of Pectinophxyra gossypiella during many evenings 



