SUCKING INSECTS 



271 



its way towards the center of the fruit, eventually causing 

 it to drop. Sometimes it also stings the fruit of the apple, 

 pear, and quince, causing the formation of knotty fruit. 

 The apple curculio also works in a similar manner. 



Regular spraying with arsenical poison is generally effec- 

 tive in controlling these insects. When the beetles are 

 very numerous they may be 

 quickly reduced by jarring 

 the trees very early in the 

 morning, beginning soon after 

 the fruit begins to set. The 

 larger branches are knocked 

 with a padded pole and the 

 curculio curls up when it 

 feels the sudden jar, drops 

 to the ground, and may be 

 caught on a white sheet 

 spread beneath the tree. 



Sucking Insects. The sucking insects do not chew or 

 eat any portion of a plant, but with their long tubular 

 mouth parts they pierce its surface and suck its juices. 

 Plant lice and scale insects are common examples of this 

 group. It is impossible to poison their food by spraying 

 with arsenical poisons. In dealing with such insects, it 

 is necessary to use a contact spray ; that is, one that will 

 kill when it strikes the body of the insect. The most 

 common spray of this class is the lime-sulphur spray used 

 against the San Jose scale. Various tobacco extracts or 

 nicotine sprays used in killing plant lice are also examples 

 of contact sprays. Sucking insects are very difficult to 

 destroy as it is necessary to hit each insect with the spray. 

 Therefore, thoroughness in spraying is essential to success, 



Fig. 145. Plum tree curculio. a, larva ; 

 b, pupa ; c, mature beetle ; d, curculio 

 on young plum. 



