THE PLUM. 115 



common at the West, but has not appeared in 

 New England. 



The Plum Sphinx and several other caterpil- 

 lars feed upon the leaves of the plum to some 

 extent, but have not proved numerous enough to 

 cause serious injury. Hand picking is, thus far, 

 a simple remedy. 



The peach borer, the flat-headed apple borer, 

 the pear blight beetle, the apple tent caterpillar, 

 the forest tent caterpillar, the canker-worm, the 

 fall-web worm, and the pear slug do more or less 

 injury to the plum, and are to be treated as sug- 

 gested for the apple and pear. The codling 

 moth sometimes injures the fruit. 



The Black Knot or Plum Wart is a disease 

 far more troublesome to the plum, and, to some 

 extent, the cherry, than all other evils excepting 

 the curculio. The cause of the disease is yet 

 unknown, although it is conjectured to be fun- 

 gous growth. Though the excrescences often be- 

 come a harbor for insects, yet it is certain that 

 these are not the cause. That it does not spring 

 from an enfeebled condition of the tree would 

 seem to be indicated by the fact that if the warts 

 are quickly cut out and destroyed, wherever they 

 appear, the tree retains its health. Usually this 

 is an effectual remedy, but a thoroughly affected 

 tree should be rooted up at once. 



