June, '13] TOWNSEND: COTTON SCALE 325 



must be made for a dry-season enemy in Mexico or Australia, or both. 

 If the native eoecinellids can not be handled as above outlined, it is 

 certain that the Japanese species can not be so handled. But eoeci- 

 nellids must certainly exist in Lower California and western Australia 

 that can be so handled. 



Cultural Control Measures 



The investigations so far made in Piura indicate three important 

 cultural measures that may be employed to advantage by the indi- 

 vidual ])lanter for the control of the .piojo ])lanco on cotton. They 

 may be outlined as follows: 



(1) Cut out all infested plants other than cotton, such as castor 

 bean, willow, melon, pigeon pea, l^eans, weeds, etc., since the cotton 

 is continually reinfested from such plants. The scale appears to 

 flourish at times on these plants when it has died out on the cotton 

 in the vicinity, and thus such i)lants constitute a reservoir of infesta- 

 tion. Such reinfestation is especially liable to take place at the be- 

 ginning of the dry season. Therefore such plants should ))e cut out 

 during November and December and burned. 



(2) Apply all the water that the cotton plants can stand without 

 interfering with the proper rij)ening of the IjoUs and the gathering of 

 the crop. The more water that can be applied to the fields the better, 

 especially during the dry season. This has two results: (a) It stim- 

 ulates the growth of the cotton plant so that it can better resist the 

 attack of the scale; and (b) it supplies the necessary degree of atmos- 

 pheric humidity in the fields requisite to maintain the parasites and 

 enemies in active and effective condition. In carr3-ing out this meas- 

 ure, it must be borne in mind that the cotton plant yields best if water 

 is withheld during the maturing of the bolls, even to the point of 

 practically drying out the soil; that ai}plication of water must be 

 regulated to the physical constitution of the soil treated; and that a 

 large pari of the crop comes during the first half or more of the dry 

 season, at just the time of 3'ear when it is particularly desirable to 

 increase the humidity in the fields for the purpose of fostering the 

 activity of the enemies of the scale. Again water is often not avail- 

 able when wanted, especially in the Piura valley during the first part 

 of the dry season. All these i)oints must be taken into consideration 

 for operations in each district where practicable to employ this meas- 

 ure, and its advantages and disadvantages weighed against each other 

 in accord with the conditions which govern that district until the 

 l)roper balance of operation is struck. Careful laborator}' and field 

 station experiments are especially needed to determine these oj^er- 



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