MARKET DISEASES OF APPLES, PEARS, QUINCES 39 



Northwest and on the Pacific coast generally than elsewhere. It has 

 been reported as seriously affecting pears of the Flemish, Bartlett, 

 Louise, Anjou, and Idaho varieties in Washington and Oregon 

 and is known to occur sometimes on quince, cherry, and plum in 

 various parts of the country. On the market it is found chiefly 

 on apples from Washington, Oregon, and California, the varieties 

 most often affected being Jonathan, Grimes Golden, Winesap, 

 Gravenstein, Yellow Newtown, Ben Davis, Gano, and Esopus 

 Spitzenburg. 



Control of the disease depends mainly on proper spraying with 

 commercial lime-sulphur or other sulphur sprays. {9, 63, 64, 100, 



114, 1^0.) 



PLUM-CURCULIO INJURY 



(Conotrachelus nenuphar Hbst.) 



OCCURRENCE, SYMPTOMS, AND EFFECTS 



Injury caused by the plum curculio is often found on apples in 

 the eastern half of the United States. A very common type of mark 

 is a fan-shaped scabby or corky area, varying in size from an eighth 

 to a half inch across. When the adult curculio punctures the apple 

 and lays its egg, the puncture is then partially surrounded by a small 

 crescent-shaped slit. As the fruit grows, this forms a corky, rus- 

 seted scar. The punctures made for the purpose of feeding are 

 smaller and do not develop into fan-shaped areas. When abundant, 

 this scarring causes the apples to be badly deformed and misshapen 

 (pi. 21). In the fall adult curculios of the new generation often feed 

 on the ripening fruit, causing shallow pits, mostly around the calyx 

 and stem ends (pi. 20, E). These do not have opportunity to heal 

 over, and may permit the entrance of decay organisms. 



CAUSE 



The adult plum curculios are hard-shelled beetles with long snouts. 

 They hibernate in the adult stage in trash in the orchards, or in brush 

 or waste land nearby, and begin to return to the apple trees about as 

 they come into bloom. Most of the egg laying and feeding is done 

 during a period of 4 to 6 weeks after petal fall, although a limited 

 amount of feeding is done in the fall. Many of the larvae in the 

 fruit are killed by the pressure of the rapidly growing tissue, but 

 enough of them survive in fallen fruit to maintain the infestation. 



CONTROL MEASURES 



The curculio may be rather readily controlled by thorough spray- 

 ing with lead arsenate during the month following petal f all.^ Some 

 State experiment stations recommend, in addition to the regular 

 codling-moth applications at petal fall and a month or so later, two 

 special curculio applications, one 7 days and another 17 days after 

 petal fall. In lighter infestations a single special application 10 

 days after petal fall appears to be sufficient. 



^As to the use of lead arsenate, particularly with regard to spray residue, see the 

 first paragraph on Control Measures, under Codling-Moth Injury, p. 22. 



