ARIZONA WILD COTTON WEEVIL. 11 



ditches all leave the washes at points very close to Thurberia plants 

 and in some cases among weevil-infested plants, it is quite easy to see 

 the probable importance of this method of irrigation in introducing 

 weevils and weevil-infested bolls directly into the fields. 



It is also the custom of a number of ranchers down in the river 

 valleys to allow their land to be flooded whenever possible in order to 

 secure the soil deposit as well as moisture. While these places are 

 farther from weevil sources it is quite possible for weevils to be intro- 

 duced in this manner. 



At present the cotton cultivated near Tucson is practically all north- 

 west of the city near the Santa Cruz and Rillito Rivers. The near- 

 est mountains in which we have found the weevils are the Santa 

 Catalinas, and at the western end these drain more or less directly 

 into the valley now cultivated. Pima Canyon and the small washes 

 adjoining it drain slightly west of south into the Rillito and thence 

 directly into cotton land. The northwestern slope at this end of the 

 range, including Montrose and Romero Canyons, drains into the 

 Canada del Oro, and this water flows southwest into very nearly the 

 same territory. The drainage of the entire southern slope of the 

 Catalina Range is thickly infested with the weevils, which frequently 

 extend along the "washes" very nearly to the Rillito. There is no 

 doubt that every season a number of weevils are washed down into 

 this country, and any cotton cultivated in this part of the Rillito 

 Valley will be in constant danger of infestation. On the east the 

 Tanque Verde Mountains supply a stock of weevils carried down 

 toward the village of Tanque Verde, while southeast of Tucson, near 

 Vail and Irene, the headwaters of the Pantano are furnished with 

 weevils from the ends of the Rincon and Santa Rita Ranges. South 

 of Tucson in the valley of the Santa Cruz the drainage from the north- 

 western slopes of the Santa Ritas contains weevils and Thurberia 

 plants well down toward the river itself. West of Tucson there seems 

 to be very little danger other than that from the end of the Catalinas, 

 as the Tucson and other ranges here seem unable to support the plant. 



Under the existing circumstances there seems to be no. measure 

 which can be taken to prevent the introduction of the weevil into 

 cotton fields, but a close watch should be continued at all times in 

 order that an attempt may be made to control them as soon as they 

 appear. Planters should maintain a careful watch for either flared 

 or fallen squares and bolls in the field and examine them for either 

 the feeding punctures or larvse of the weevils. This observation 

 should be especially close in fields or parts of fields adjacent to water 

 courses carrying drainage from situations such as those described as 

 normal for Thurberia. 



At the present stage of the investigations it is impossible to pre- 

 dict just what the extent of the damage by the weevils will be when 



