10 BULLETIN" 233, U. S. DEPARTMENT OF AGRICULTURE. 



all very rapid in descent near the mountains, and very rocky, so that 

 comparatively little of the water seeps into the ground in this part 

 of the journey and the force of the current scours the channel clean. 

 Just above the ranch the character of the stream bed changes and 

 it becomes wide and sandy. Here the water seeps rapidly and prac- 

 tically every flood of the present season was able to reach but little 

 below the ranch in this sand. Hence the Thurberia bolls containing 

 weevils may be expected to pass through the rapid part of the stream 

 and be deposited on the sand where the flow stops near the ranch. 

 It was probably some such procedure as this which caused the infes- 

 tation of the experimental cotton during the season of 1914, and the 

 possibility of future infestation will always be present. 



PROSPECTS. 



From the various observations reported herein it seems quite evi- 

 dent' that it is only a matter of time until the weevil will appear on 

 the cotton cultivated near Tucson. The territory best adapted for 

 the cultivation of cotton and that upon which it seems most likely to 

 be raised is nearly all within easy reach of the floods from weevil- 

 infested territory. While it is obviously impossible to state that the 

 infestation will appear at a certain point, there are many places more 

 liable to infestation than others. Such a location has been described 

 at the ranch where the cotton was infested and a number of similar 

 ones occur along the mountain slopes. The fact that the experimen- 

 tal cotton was. infested during 1914 demonstrated the importance of 

 such a situation, but, on the other hand, it is by no means certain 

 that the infestation would be repeated each season. However, the 

 movement of the weevils out into the plains which takes place every 

 year must sooner or later result in the infestation of cultivated cotton 

 in the valley. These weevils which are washed into the field can do 

 comparatively little damage themselves, but the result to be feared 

 is that their progeny will become established in the valley, will winter 

 there, and will become more and more adapted to injuring cultivated 

 cotton. 



Another point which is likely to be of prime importance in the trans- 

 fer of the weevil is the practice among many ranchers of using these 

 floods for irrigating their land. A ditch is opened from the arroyo 

 and in time of flood the water is diverted into this ditch and conveyed 

 to the cultivated land. Agua Caliente arroyo is tapped in this manner 

 near one corner of the Agua Caliente ranch and the water is led off to 

 a ranch on the west side of the stream bed. Soldier's Canyon arroyo 

 is tapped in the same way about one-half mile from the mouth of the 

 canyon and the water is carried off to the southwest through several 

 homesteads. The water from Sabino and Bear Canyons is used in 

 the same way near the junction of the two arroyos. Since these 



