F? 1 ,,//"«"««--... If? »fr. l oited States Dep^wiSS^'lgriculture, BUREAU OF ENTOMOLOGY. I . i i. HOWARD. I ntomologUi tnd Chid <•( D Circular No 146. THE MOVKMKNT Of THE HEXICAN COTTON BOLI nt.iyil in 1911. By \V. l». in n In Charge of Southern Field Crop Insect Invent iff dlionT. Daring the Reason <>f 1911 the boL weevil was greatly reduced in lumbers throughout its entire range. This resulted from a com- bination of climatic influences extending over a period of about tlnvc year-. So unfavorable were the conditions that the insect was exterminated in an urea covering about 23,000 square miles in the northwestern portion <>f Texas and the western portion of Okla- homa. Undoubtedly these conditions had an important bearing on the production of the large crop of 1911. The unfavorable condition- for the weevil which culminated in 1911 began in L909. In that year drought occurred in Texas and Louisiana at such a time a> to check the development of the imma- ture stages. In 1910 equally adverse conditions prevailed, and the pe-t was further reduced in numbers. At the end of the season of 1910 condition- arose which gave the insect another very important ■etback. This was a killing frost which occurred October 29. The Weevils were deprived of their food in all parts of the infested terri- tory except along the Gulf Coast and in a few isolated localities else- where. The freeze destroyed outright enormous numbers of the ils which wire found in the bolls and squares, but the conditions immediately following the freeze were even more Important in re- ducing the infestation to a very low point. After the freeze of O I tier 29 the weather became warm, and this induced activity on the part of the weevil- that survived. In fact, temperature- occurred for several week.- which caused the in-eci- i ire food. An active search for food began, but as the cotton had all been killed the ma- jority of the weevil- which had survived the f"iveze could find no food and perished. •— ^ / (Mr. 140 — 12 / ■ -• 2 THE MOV KM EST OF THE ROLL WEEVIL IN 1911. The general effect hi Hie cold of Oct ok -r 29 is shown by a study of the conditions in certain localities which were exempt from freezing temperatures. In several counties in the vicinity of Cisco, Tex., for some unexplained reason, the first killing frost in 1910 did not occur until November 29. At this time m6s1 of the weevils were in hiber- nating quarters. As a result, in 1911. it was found that in the vicinity of Brownwood there was an area in which the weevils were numerous and in Avhich considerable damage was done. This area corresponded exactly with the area in which the freeze of October 29 was not experienced. The great reduction in the number of weevils which succeeded in passing the winter of 1910-11 is shown by hibernation experiments which were conducted at Tallulah, La. At this place it is determined that one-half of 1 per cent of the weevils which entered hibernation emerged in the spring of 1911. In favorable seasons as high as 12 per cent hav e survived in that locality and, in fact, the average sur- vival during seven different seasons in seven widely separated locali- ties in Texas and Louisiana has been 7 per cent. The region in which the boll weevil became exterminated in 1911 is the one in which the conditions of drought were most intense in 1909 and 1910 and in which at the same time the conditions for hibernation are less favorable than in other parts of the cotton belt. The territory where the loss occurred consists generally of open country in which but little timber is to be found. Notwithstanding the great reduction in the numbers of the boll weevils in the United States in 1911 considerable advance was made to the east and north when the dispersion movement began in August. The explanation of this lies in the outbreak of the cotton caterpillar, which defoliated practically all of the fields throughout the infested area at about the time the dispersion movement was beginning. The weevils started on their dispersion flight, encountered fields which had been stripped by the leaf worm, and continued their flight indefi- nitely. If the fields just beyond the border of the previously infested territory had not been defoliated the weevils would have stopped and the total area covered would have been much less. This extensive dispersion of the insect caused it to regain much of the territory it had lost in Texas and Oklahoma, and Florida became invaded for the first time. (See map, fig. 1.) The reasons for the great scarcity of weevils in 1911 are plain. The reduction was due to a combination of climatic influences which can only be expected to recur at very infrequent intervals. With the return of seasons favorable to it the boll weevil will un- doubtedly regain all of the lost territory and multiply to the same extent as it has in the past. It must not be supposed from the situa- Ill i MOV1 \i I \ n I BOI I. WEEVIL IN 1911. UNIVERSITY OF FLORIDA 4 3 1262 09216 5827 THE MOVEMENT OF THE BOLL .. ~.~.*^ **, ^^. tion in 1911 that there is any hope whatever for a permanent reduc- tion in the importance of the boll weevil. On the contrary, it is nec- essary for planters to continue their fight against the pest according to the plans that have been detailed in the publications of the Depart- ment of Agriculture. Approved: James AVilson, Secretary of Agriculture. Washington, D. C. January 3, 1912. o