58 PLANT-BUGS INJURIOUS TO COTTON BOLLS. 



19,000 acres — would average between 0.063 and 0.079 bale per 

 acre. It is certain that this estimate was not too high, as it was 

 based solely on the damaged and ruined bolls in evidence in the 

 cotton fields at the close of the picking season and no consideration 

 whatever w^as given to the bolls shed as a result of the injury by the 

 insects. In the season of 1904 fewer of the bugs were present than 

 in the preceding season and the average yield per acre of planted 

 cotton amounted to 0.472 bale per acre, being an increase of 0.161 

 bale per acre. This increase is believed to be partly due to the differ- 

 ence in the number of bugs present in the cotton fields in the two 

 seasons referred to. 



In July and December, 1905, field observations throughout the 

 plantation of over 22,000 acres at Tlahualilo gave data from which 

 it is believed an estimate of damage has been made which is more 

 accurate than any estimate of insect damage based on actual field 

 examination ever attempted for as large an acreage. It was found 

 that bug damage ranged from none at all in restricted areas to 31.6 

 per cent and for the entire plantation averaged very close to 8 per 

 cent. This does not include the bolls which were shed from the 

 plants. These numbered probably less than 2 per cent and their 

 loss was not necessarily detrimental to the crop as they did not, 

 like those damaged bolls that persisted, continue to receive nutri- 

 ment from the plant. The entire yield at Tlahualilo in 1905 amounted 

 to about 15,000 bales. The loss of about 8 per cent represents, 

 therefore, about 1,200 bales of cotton. The methods used in the 

 examinations upon which this estimate is based will be explained 

 hereafter. 



A striking contrast to the conditions at Tlahualilo was observed 

 about 40 miles distant in the southwestern portion of the Laguna 

 district near the cities of Gomez Palacio and Lerdo. Here, for some 

 obscure reason, persistent search failed to show the presence of the 

 conchuela while other plant-bugs were of remarkably rare occurrence 

 in cotton fields. As a consequence plant-bug injury was difficult 

 to find and, at the most, amounted to only a small fraction of 1 per 

 cent. 



The most detailed study of the losses due to plant-bugs was made 

 at the Tlahualilo plantation in 4 blocks heretofore referred to, namely, 

 Ceceda A 14, Zaragoza Bl, Zaragoza B2, and Zaragoza B3. In the 

 first the work extended throughout the block while in the last 3 

 blocks the studies were local and represented in each case conditions 

 which may have been characteristic of only a small part of the entire 

 block of 120 acres. In July, 1905, many examinations of green bolls 

 were made for the purpose of determining the percentage of damage, 



