THE PLUM CURCULIO IN APPLES 29 



round and slightly smaller than the head of a pin. A scab and scar, similar 

 to that following an egg puncture, develop except that the scar tends to be 

 round and slightly smaller. 



Most scars from both egg punctures and early feeding punctures are 

 superficial and seldom decrease the keeping quality of the apple, but under 

 the prevailing grading rules they reduce the fruit to the second or third 

 grade. 



The Burrow of the Larva extends through the fruit to the core, and 

 causes the apple to fall early in its development. The tunnel resembles that 

 made by the codling moth except that the feeding is more confined to 

 the core. 



Equally or more important than the injury by the larva is the fact that 

 practically all apples, in which grubs develop, fall to the ground early in the 

 summer. Many apples which are badly stung but contain no living grubs 

 also fall. In the experimental orchard in 1927, 85 per cent of the fruit on 

 unsprayed trees dropped before harvest. Eighty-three per cent of these "drops" 

 showed curculio injury. On adjacent sprayed trees only 46 per cent of the fruit 

 dropped and this fruit showed 12 per cent curculio injiuy. Other insects 

 and diseases attacked the unsprayed fruit in this orchard, but the greater 

 part of the excessive drop was attributed to curculio injury. 



Tunnels in which the grubs have died close, leaving a thin brown line. 

 Growth is slowed up or stopped in this region causing a depression in the 

 outer surface of the fruit which considerably reduces its quality. Many of 

 the apples injured in this manner remain on the tree. 



Late Feeding Punctures are made principally by the fall-emerging beetles, 

 although a few of the overwintering beetles may continue to feed at this 

 time of year. The punctures through the skin are circular and about the 

 size of a pinhead with a cavity in the flesh underneath equal in diameter to 

 the length of the beetle's beak. The skin sruTounding the entrance and 

 covering the cavity turns black and the injury offers a favorable point for 

 fungous infection. Many sou'nd apples are injured by this type of feeding 

 even though the beetles prefer mellow or blemished fruit. 



DESCRIPTION (Non-Technical) 



Like other beetles, the plum curculio passes through four stages of growth 

 in its development, namely: the egg which is laid under the skin of the 

 fruit, the larva or grub which feeds in the flesh of the fruit, the pupa or 

 resting stage which is passed in an earthen cell, and the adult or beetle 

 which develops from the pupa. Figure 2 illustrates the general appearance 

 of the different stages. 



The pearly white Egg is elliptical in shape, slightly less than 1/25 of an 

 inch long and about half as wide. The smooth, shiny outer skin is moderately 

 tough but so soft that the egg is easily crushed by the pressure from the 

 growing fruit when not protected by the flap of the crescentic cut. 



The full grown Larva is a plump, yellowish-white, legless grub from H to 

 y2 inch long. The body is curved toward the under side with fleshy lobes 

 resembling swellings on the sides of the middle segments. The head is Hght 

 brown, shiny, and about half as wide as the thickest part of the body. 



The creamy white Pupa is approximately Ya of an inch long. It has the 

 general shape of the beetle with legs, beak, and partly grown wings folded 

 tightly against the body. The black eyes are prominent. 



