24 



BULLETIN 1320, U. S. DEPARTMENT OF AGRICULTURE 



LATER WEEVIL INJURY 



The first indication of weevil infestation in the late-planted cotton 

 was noted on July 8, after the plants had begun to produce flowers. 

 It is probable that this infestation resulted from migratory or stray 

 weevils from the nearest field of early-planted cotton. A field of 

 cotton planted on April 12 was located about 200 feet southwest of 

 the late-planting test. This early-planted cotton was heavily 

 infested with weevils, and migration may have occurred from this 

 field during the first part of July. 



In order to show the progress of infestation in the late-planted 

 cotton, a record was obtained of the number of weevil-punctured 

 squares which were shed from the plants in two 50-foot sections of 

 rows. The number of squares shed each day are graphically pre- 

 sented yi Figure 8. The first squares shed as a result of weevil injury 

 were found on July 11. The shedding was very slight until July 25, 

 when a rapid increase occurred. The sudden increase at this time 



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Fig. 8.— Number of weevil-punctured squares shed from a 100-foot section of row in cotton planted on 

 April 22 and on May 12 at San Antonio, Tex. The upper line represents cotton planted on April 22; 

 first squares on May 27. The lower line represents cotton planted on May 12; first squares on June 10. 

 No treatment for the control of weevils was given in either field 



was probably due to an increased infestation by weevils migrating 

 from near-by fields of early-planted cotton. 



A similar record of weevil-punctured squares was obtained from 

 a field of cotton planted on April 2, located about 600 feet north of 

 the late-planted cotton. These data are included in Figure 8 for 

 purposes of comparison with data regarding the late-planted cotton. 



The first squares on the cotton planted April 22 appeared during 

 the last week in May. Weevils were found on plants in this field by 

 June 1, and a 12 per cent infestation was recorded on June 6. As 

 squares were available early in June, it was possible for the weevils 

 to deposit eggs and insure the appearance of a new generation of 

 weevils by the latter part of the month. Thus, the May 12 planting 

 did not get weevils for more than a month later than the April 22 

 planting, and the breeding of an early generation of weevils during 

 June was entirely avoided in the late-planted cotton. 



Even if favorable conditions for natural control of weevils did not 

 occur, effective control might be obtained in late-planted cotton by 

 applying poison just before squares are produced. This method of 

 control probably would be limited to late-planted cotton which did 



