402 ANNUAL, REPORT OF THE Off. Doc. 



THE PLUM CURCULIO. 



(Conotraclielus nenuphar Herbst.) 



The plum curculio is the cause of more loss to plum growers in 

 this State than all other insects combined, fifty, sixty or even sev- 

 enty-five per cent, of the plums often being destroyed by its attacks. 

 Quite a part of this loss can be avoided, however, by using the proper 

 methods, while if these are neglected the insect as it becomes more 

 abundant in an orchard will also attack apples, pears, cherries and 

 peaches, injuring the appearance of these fruits and thus lessening 

 their value, even when it does not prevent their reaching maturity. 



Life History. 



The plum curculio in its adult state is a little beetle about a quar- 

 ter of an inch long, dark in color but with a few whitish markings on 

 its roughened back, and with a snout on its head. It passes the 

 winter hiding in any protected place it can find, and makes its ap- 

 pearance about the time the leaves open in the spring. While wait- 

 ing for the plums to form, it feeds on the young leaves somewhat 

 though doing little damage in this way, but w^hen the blossoms have 

 fallen and the plums have begun to grow, it proceeds to lay its eggs. 

 To do this, it makes a small hole in the plum with its snout and in 

 this hole it deposits an egg. It appears to realize, however, that un- 

 less farther precautions are taken, the rapid growth of the hard 

 young plum will crush and destroy the egg, and it therfore cuts a 

 crescent-shaped slit near wiiere the egg was placed. The result of 

 this is that the flesh of the plum between the egg and the slit wilts 

 and remains soft, and crushing of the eggs is thus prevented. Each 

 curculio lays from fifty to one hundred eggs in this way and plums 

 with six or eight slits and egg holes are frequently observed. 



The eggs thus laid soon hatch and the young grubs eat into and 

 around the stone, while the surface of the plum where the slits were 

 made becomes gummy. 



Around the stone the grub feeds till it is full grown, the time re- 

 quired for this being usually about three weeks. The grub then 

 leaves the plum (which frequently falls oft" before this time, because 

 of the presence of the grub) and enters the ground where it becomes 

 quiet and transforms to a pupa from which the adult curculio ap- 

 pears a month of more later. Apparently this curculio does no in- 

 jury during the remainder of the summer and fall but appears after 

 wintering in some secluded place, to lay its eggs the following 

 spring. 



