INSECTS OF THE PLUM 281 



Scab. — The scab on the plum is a disease somewhat similar 

 to that found on the apple. The scab of the plum is also 

 found on the peach and the apricot. The disease is char- 

 acterized by numerous small, circular, dark- colored spots, 

 usually found on one side of the fruit, but sometimes it 

 c()\'ers the entire fruit. The twigs and the leaves are also 

 affected. Bordeaux mixture is usually able to hold this 

 disease in check. 



INSECTS OF THE PLUM." 



The plum is attacked by several insects, some of which 

 are particularly destructive to it alone like the plum curculio, 

 while others are more or less destructive to all stone fruits. 

 The San Jose scale and the fruit Lecanium scale are some- 

 times particularly troublesome. 



Curculio. — ^The plum curculio is the worst insect enemy 

 of the plum. The curculio is primarily an enemy of the stone 

 fruits, but also attacks the apple, the pear and the quince. 

 It is by far the most destructive insect with which the grower 

 of the stone fruits has to contend. In some regions it often 

 destroys the entire crop in an unprotected orchard. 



The curculio is a small snout beetle about one-fifth of an 

 inch in length, mottled with black, gray and brown. The 

 beetles attack the fruit as soon as it is set. Two kinds of 

 punctures are made — those for the reception of the egg and 

 those for feeding. 



The feeding punctures are only small holes, which are 

 about one-eighth of an inch deep. The egg-laying punc- 

 tures are much different. A small hole is made in the fruit 

 with the snout and the egg is laid in this hole. After 

 the egg has been deposited the female cuts a crescent- 

 shaped slit under the egg, to protect it from injury while the 

 plum is growing. This way of depositing the egg allows it to 

 develop in a flap of flesh. The egg laying continues over a 

 long period and sometimes it lasts throughout the entire 

 season. However, in most cases the greater number of eggs 

 are laid the first month after the females come out of their 

 winter quarters. 



The first step in the control of this insect is to clean up 



