182 



MANUAL OF GARDENING 



217. Canker-worm. 



cation of poison to the parts 

 that they eat. It is apparent, 

 however, that insects which 

 suck the juice of the plant 

 are not poisoned by any 

 liquid that may be applied 

 to the surface. They may 

 be killed by various mate- 

 rials that act upon them ex- 

 ternally, as the soap washes, miscible oils, kerosene 

 emulsions, lime-and-sulfur sprays, and the like. 



There has been much activity in recent years in the 

 identification and studj'^ of insects, fungi, and micro- 

 organisms that injure plants; and great numbers of 

 bulletins and monographs have been published; and 

 yet the gardener who has tried assiduously to follow 

 these investigations is likely to go to his garden any 

 morning and find troubles that he cannot identify and 

 which perhaps even an investigator himself might 

 not understand. It is important, therefore, that the 

 gardener inform himself not only on particular kinds 

 of insects and diseases, but that he develop a re- 

 sourcefulness of his own. He should be able to do 

 something, even if he does not know a complete 

 remedy or specific. Some of the procedure, prevent- 

 ive and remedial, that needs always to be considered, 

 is as follows: — 



Keep the place clean, and free from infection. 

 Next to keeping the plants vigorous and strong, 

 this is the first and best means of averting 

 trouble from insects and fungi. Rubbish and 

 all places in which the insects can hibernate 

 and the fungi can propagate should be done 

 away with. All fallen leaves from plants that 



