362 



THE AGRICULTURAL NEWS. 



November 17, 1917. 



INSECT NOTES. 



THE PINK BOLL WORM. 



In the last number of the Agricultural Nen's the present 

 known distribution of the pink boll worm was briefly 

 touched upon, and reference was made to the enormous 

 losses to the cotton industry which this pest is causing in 

 some countries. An account was also given of the life-history 

 of this pest, and of the habits of the moths, as observed by 

 Mr. Busck, of the United States Bureau of Entomology, while 

 studying this insect in the Hawaiian Is'ands In the present 

 number it i.s proiiosed first of all to refer to some of the 

 habits of the pink boll worm itself as observed in Hawaii 

 under artificial conditions, and then to touch upon the way 

 this pest is spread, giving examples to demonstrate the 

 necessity of strict quarantine meisures in countries as yet 

 uninfested by Pectivoph(jra gossypielta. 



LONGEVITY OF THE t^ARVA AND BEHAVIOUR UNDER 

 ARTIFICIAL CONDITIONS. 



As Stated in the former article, the larval stage lasts 

 from twenty to thirty days under normal summer con- 

 ditions, but experiments and observations in Hawaii 

 have shown that if the young larva is confined to dry 

 and hard cotton seeds, either artificially, or, as may 

 happen, in prematurely ripening bolls in the field, it will live 

 much longer. In one experiment, heavily infested, unpin- 

 ned seeds were baled under strong pressure into small 

 trial bales (24 by 12byl^! inches) in September 191.5, 

 and placed in dry rearing boxe.'^ in Honolulu. One of these 

 bales was examined every month afterwards, and numbers 

 of healthy larvae were found on each examination up to 

 March 1917. This experiment showed that the larval life 

 of the pink boll worm may be suspended over a period of 

 eighteen months. This ability of the larva to live within the 

 seeds over such a long period has an important bearing on 

 the spread of the species, since the larvae may be carried any 

 distance in cotton seed, and may then complete their 

 development, and produce moths capable of starting an out- 

 break in a new country 



In the account of the life-history given in the last 

 issue it was mentioned that the larva of the pink boll 

 worm, before pupating, bores a hole through the husk 

 of the boll, thus allowing the issuing moth to escape. 

 Experiment.s have .shown that this instinct governs the larva 

 under artificial conditions also. For instance, it has been 

 observed that if an infested boll is wrapped in paper or cloth, 

 the larva will still make a hole to the outside, and then spin 

 its cocoon within the hole. Again, if a mature larva is confined 

 in a pillbox or in a capsule, it will bore its way through, and 

 then probably form its cocoon inside. Further, when green 

 infested bolls are inclosed within a sack, the mature larvae will 

 leave the bolls, and e\t their way through the .sack to pupate 

 in more favourable places outside. It has also been found 

 that if a larva matures within a bale of dry cotton, and 

 happens to be sufficiently near the surface to get through the 

 packed cotton, it will eventoally cut its way through the 

 coverini; of the bale, but will not normally pupate within 

 the hole in the covering. Such a larva will seek a suitable 



place outside, because of its instinct to procure a firm 

 support for the issuing moth. 



The above instances show that the pink boll worm is an 

 exceedingly dangerous pest, for not only can the larva live 

 for considerably more than a year in stored cotton seed, or 

 even baled cotton carrying chance seeds, but it can also, 

 when favourable opportunity offers, cut its way out, complete 

 its development, and fly away as a moth to start an infes- 

 tation in Its new home. Like so many other insect pests the 

 pink boll worm can never be eradicated when once it has 

 become established, and it is therefore all the more important 

 to impose such quarantine measures as will effectually 

 prevent its introduction 



MANNER OF DISPERSION. 



It has been observed by Mr. Busck that while the 

 moth of the pink boll worm {Fectinophora gossypiella) is 

 capable of a strong, darting flight, yet it is rather too 

 sluggish for sustained flight, so that it does not spread to 

 any great distance by this means, but only to adjacent fields. 

 It is true that under favourable conditions such larvae or 

 moths which may chance to be in loose cotton lint might be 

 carried for a considerable distance by a strong wind, but 

 ordinarily the wind does not play an important part in the 

 spread of this pest. From what has been previously written 

 about the habits of the larva, it may be guessed that man is 

 the most imprrtant agent in the dispersion of this insect, 

 when he imports cotton seed or bakd cotton from one con- 

 tinent to another, and then proceeds to distribute the impor- 

 tations over large areas without previous inspection, 



In this connexion an article in the Scientific American 

 for August 4, calls attention to the fact that the area in the 

 Laguna District of Mexico infested by the pink boll worm is 

 much larger than was at first supposed, and that seed has 

 been distributed from this district to other districts, thua 

 spreading the area of infestation in Mexico. In the course 

 of this article Mr. Houston, Secretary of Agriculture in the 

 United States, al.so mentions the establishment of a cotton 

 seed oil mill in a town on the Mexican- Tnited States border, 

 to which large (|uantities of seed infested by the worms are 

 being moved, and states that moths have been emerginij 

 from the .seed stored at this border town within a few miles 

 of Texas cotton fields. The infestation of the Texas coiton 

 fields by the pink boll worm would seem to be only a matter 

 of time 



The recent establishment of this cotton pest in Brazil 

 is referred to in a short article in Science for March 23, 

 1917. It seems that the Brazilian Government, in order 

 to encourage the cultivation of Egyptian cotton in that 

 country, sent an agent to Egypt who shipped large quan- 

 tities of seed to Brazil. On its arrival it was distributed 

 by a branch of the Ministry of Agriculture to inspec- 

 tors in every State, who in turn distributed it free to 

 all applicants. Dr. W. 1). Hunter, the writer of this article, 

 goes on to remark that a more thorough method of dissemi- 

 nation of an insect in a new country could hardly be devised. 

 In fact, so well v,as the pest distributed, that in a period of 

 less than three years it has become generally and thoroughly 

 established in the cotton belt of Brazil. In some localities 

 the yield of cotton was reduced by half. The eradication of 

 the pink boll worm from Brazil has now become impossible, 

 and it is only through the most strenuous measures in the 

 future that the cotton industry in that country will be able 

 to survive. 



These instances show how easily a pest like the pink 

 boll worm can become established in a new country, and only 

 serve to emphasize still more strongly the importance of 

 quarantine measures. 



