234 



THE AGRICULTURAL NEWS. 



July 26, 1919. 



INSECT NOTES. 



SPREAD OF THE MEXICAN BOLL 

 WEEVIL IN THE UNITED STATES- 



The progress of the Mexican boll weevil eastward, across 

 the cotton belt of the United States, has been noted from 

 time to time in the Agricultural Neivs. 



The spread of this insect in 1917 was noted in this 

 Journal for September 21, 1918 (Vol. XVII, p. 298), when a 

 net gain of 7,300 square mile.s of territory was recorded. 

 The story of the boll weevil spread in 1!)18 is a diliVrent one 

 from that of 1917. Instead of a gain in territory, the insect 

 gufTered a setback, and the weevil-infested territory at the 

 end of 1918 was .■S0,.")00 square miles less than in 1917. 

 Only once before during the history of the invasion of this 

 insect into the United States Las it happened that the 

 infested area has been less at the end of a year than at its 

 beginning. That happened in 1896, the fifth year of the 

 invasion. 



The total loss of territory by the weevil ia 1918 

 amounted to 46,600 square miles, and the gains to 16,100. 

 a net loss of 30,500 square miles. 



The extremely cold winter of 1917-18 was responsible 

 for the death of the weevils over a very large area in a 

 belt along the northern and western limits of infestation. 

 Much of this territory was reinfested during the year 1918, 

 but on account of early frosts in the autumn, and extreme 

 drought, the weevils had failed to reinfest some 46,600 

 square miles. The gains were made in those eastern States 

 wLere Sea Island cotton is growu, except for a small 

 infestation of 100 square miles, which marks the first 

 appearance of this insect in New Mexico. 



The southernmost limit of cotton cultivation in Florida 

 has been reached. Of the State of Georgia, only a small 

 portion of the north remains uninfested ; and in South 

 Carolina, practically all the Sea Island cotton district is 

 infested. This means that almost the entire area in the 

 United States of America where Sea Island cotton has been 

 grown, is now infested with the boll weevil. 



The control of the boll weevil in the United States 

 has occupied the best attention of a large number of 

 entomologists and plantcs, who have been interested in 

 the matter for the jmst twenty-five years, and nothing has 

 been discovered to prevent the steady progress of this 

 insect throughout the entire cotton belt. Along the northern 

 borders the weevil has difficulty in maintaining itself on 

 account of the cold winters sometimes experienced, and on 

 the west margin, it is adversely affected by drought. No 

 natural enemies capable of exerting an appreciable check 

 on this pest have made their appearance. 



For the past six years extensive trials of control by 

 poLioning have been made, with proiiii.se of success. The 

 poison used is calcium arsenate, and it is applied by means of a 

 power duster or hand-gun. 



Id 1918, some 3.'j,000 acres of cotton were treated (see 

 Agricullural News, Vol. XVIII, p. 122, April 19, 1919) with 

 much success. The experts in charge of these trials, how- 

 ever, state that this work is in its experimental stage, and 

 planters are advised either to take every precaution to 

 make trial of it according to the best information 

 available, and with due regard to tke recommendations made, 

 "t lo leave it alone altogether. 



BRITISH GUIANA : REPORT ON THE 

 DEPARTMENT OF SCIENCE AND AGRICUL- 

 TURE FOR THE YEAR igi-. 



This report, although not published until a few months 

 ago, contains a large amount of useful information which 

 is of permanent value to West Indian agriculture. At the 

 beginning of the report Professor Harrison, (".M.G., the 

 Director of Agriculture points out that the work of the 

 Chemical Division has been seriously interfered with 

 through depletion of staff. Nevertheless it was • found 

 possible to carry out a great deal of routine work in other 

 directions, and also many agricultural iovestigations, the 

 most important of which will be referred to in the course of 

 this review. 



Valuable experiments with sugarcane were continued 

 during the year. As regards routine work, 299,360 cuttings 

 of forty-nine varieties were distributed to plantations, 

 while in addition to the cuttings, 1,910 plants of new 

 seedling varieties raised in 1916 were supplied in plant- 

 baskets to plantations having nurseries. The most popular 

 variety appears to be D.ILS. This variety in the 

 experiments gave a high yield of cane per acre ^33-1 tons), 

 while its saccharose content was 1'95- The cane with the 

 highest sugar content was D. 108, which tested 204 B). per 

 gallon. 



In the manurial experiments increased manuring with 

 sulphate of ammonia did not result favourably, although 

 lower applications resulted in comparatively large increases. 

 This was doubtless due to weather conditions. During 

 1917 sulphate of ammonia was very difficult to obtain, so the 

 Department set out to find .some form of manurial substitute. 

 Great (juantities of rice straw are produced in the Colony, 

 almost all being wasted by rice farmers. For some years 

 this straw has been used in the Botanic Gardens as 

 a mulching material, and the results have been so good that 

 the material has been recommended for use on estates in 

 place of sulphate of ammonia. The beneficial effects of the 

 rice straw arc due to three causes : (1) its direct manurial 

 action by the addition of nitrogen, [ihosphoric acid, lime, and 

 potash to the soil ; (2) its action in preventing the develop- 

 ment of weeds, especially those of the order Graminea- ; and 

 (3) by the large amount of difficultly decomposiblo woody fibr« 

 it adds to the soil, resulting in gradually rendering the sur- 

 face soil lighter and less tenacious, and hence of bettor tilth. 

 An application of 12 tons of rice straw to an acre, adds to 

 the soil the following iiuantities of the more important con- 

 stituents of [ilant fond : nitrogen (Creole rice), 70Ib. per acre; 

 (No. 175) 948). per acre; phosphoric anhydride (Creole), 

 321b., (No. 75) 320). ; potash (Creole), 2141b. ; (No. 75) 

 2311b.; lime (Creole), 38lb.; (No 75)328). The dressings 

 of rice straw produced the following excess yields : D. 625, 

 2 6 tons per acre, saccharose '40 ton per acre ; D. 118, 2"3 

 tons of cane per acre, saccharose -46 ton; D.145, 34 tons of 

 cane and '43 ton of saccharose. From the results of 

 these trials it is evident that it is worth the while of 



