326 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 6 



ation balances for the various districts, which differ largely in soil 

 conditions and water facilities; as well as for different varieties of 

 cotton, which differ as to the cropping-season possibilities. 



(3) Cut back the cotton plants immediately after the gathering of 

 the Christmas crop of the second or third year, or as soon as it is found 

 that the preceding measures are not holding the scale in check suffi- 

 ciently under the prevailing conditions to insure an average crop; 

 when cutting back is no longer practicable, on account of age of 

 plants, then replant from seed. The earlier the cutting back can 

 be done at the beginning of the dry season, the more complete will 

 be the control of the scale. The cut stalks should be burned if the 

 cutting is done in the dry season, but if it is done at any time between 

 June and October they should be simply piled up and left undisturbed 

 for a month at least. November cuttings should be burned. These 

 recommendations are made for the purpose of saving the valuable 

 parasites and other enemies that abound on and in the scale from 

 June to October, and which should not be destroyed. In carrying 

 out this measure, it has to be borne in mind that some varieties of 

 cotton can be cut back to advantage once a year, others every two 

 years, and the native tree-cotton or pais variety not oftener than 

 once in three years; and that certain districts are adapted to certain 

 varieties and not to others, on account of peculiarities of soil and 

 water-supply. Among the varieties adapted to the conditions of a 

 particular district, other conditions being equal, that variety should 

 be selected which can be oftenest cut back with advantage. Here 

 again field station experiments are necessary to determine the most 

 advantageous operative details. 



Estimated Capacity for Damage in Piura 



The area infested by the piojo bianco comprises the whole cotton- 

 region of Piura Department in the Chira and Piura valleys. A 

 conservative estimate of the acreage in cotton in these two valleys 

 would exceed 12,000 hectares or 30,000 acres. The product of this 

 region equals ordinarily about 20 per cent of the whole cotton crop 

 of Peru. As the native tree-cotton is the variety most largely cul- 

 tivated and brings the highest price, the value of the Piura crop is 

 equal to about £350,000 or nearly 25 per cent of the value of Peru's 

 total cotton crop. The Piura crop should equal, on the above acre- 

 age, an annual value of at least half a million pounds sterling. The 

 piojo bianco, if left to itself, will diminish the value of the Piura crop 

 by at least 40 per cent. Its normal possibilities for annual damage 

 in Piura are therefore in the neighborhood of £200,000. 



