80 



the ground, concerted irrigation continued for a proper lengtli of time 

 might have a marked effect on this as well as other insects and yet not 

 be found of special disadvantage to crops or fruit. 



No doubt irrigation would have little effect on the San Jose or other 

 scale insects. They can be controlled by other and more effectual 

 means, to which, as an accompaniment, irrigation would prove of no 

 value. 



lloot-borers of Apple, Quince, or Yine (grubs of Prionus californicus 

 and other species) would not be affected particularly in their tunnels 

 in the live wood of the roots, as they are at some distance below 

 ground. Besides it has recently been found that many fruit trees 

 have been killed here by over or improper irrigation, or irrigation at 

 the wrong time of day. Such soaking of the ground as would be neces- 

 sary to reach these borers would greatly injure the trees. The adult 

 beetles could not be reached by this means. 



The flea-beetle {Raltica foUacea), which is often very injurious to 

 young aijple grafts, might, from its very habit of attacking only the 

 smallest trees whose leaves are near the ground, be controlled largely 

 by proper irrigation. 



The Fall Web-worm, which is very abundant on our cottonwoods, 

 could also be controlled on such trees as are situated on irrigable 

 ground -, since the turning on of the water would kill great numbers of 

 the larv* which, so far as my observation goes here, largely seek the 

 ground for transforming. 



Such irrigation would also kill the Cottonwood Leaf-miner, referred to 

 in Insect Life (vol. iv, pp. 26-27), which I have been unable to breed 

 as yet, but which I find goes into the earth to pupate. For cottonwoods 

 situated along the roads and sides of streets, such treatment would be 

 wholly impracticable, and the only remedy for either insect would, in 

 this case, be the arsenites. 



A native harvest-fly (Cicada ochreoptera) does much damage here to 

 twigs and young branches of deciduous fruit trees, especially Pear and 

 Plum. It might prove susceptible to irrigation if the latter were ap- 

 plied at the time when the pupae issue from the ground. 



There is a considerable number of alfalfa insects, more or less injur- 

 ious, such as lepidopterous larvae, Oapsidse, leaf -hoppers, and dipterous 

 larvae, some of which would be and doubtless are extensively checked in 

 their depredations on this valuable forage i)lant by the process of irri- 

 gation. The water is not turned on high enough, however, nor contin- 

 ued for a sufficient length of time, to accomplish any effectual destruc- 

 tion of the insects. The Capsidae are apparently the least affected. 



As mentioned in Insect Life (vol. iv, p. 25), irrigation will doubt- 

 less have considerable effect on the Southern sugar-cane borer (Bia- 

 trcea saccJiaralis), many dead pupae of which were found in the roots 

 of corn on the college farm last year. 



As the Boll Worm. {Seliothis armigera) pupates in the ground, it can 

 also be largely destroyed by the same means. 



