10 MISC. PUBLICATION 168, U. S. DEPT. OF AGRICULTURE 



maggot by the use of DDT. Current recommendations of the 

 Bureau of Entomology and Plant Quarantine or of State agricul- 

 tural experiment stations should be used as a guide in working 

 out a control program for this pest. 



Experiments carried on by the New York State Agricultural 

 Experiment Station have shown that if infested fruit is held 

 continuously at 32° F. for 40 days all eggs and maggots are 

 killed. This treatment may be used in meeting quarantine re- 

 quirements relative to the shipment of infested fruit. 



(See 2, 2h, 47, 48, 101.) 



Apple-Cedar and Quince Rusts 

 {Gymno sporangium juniperi-virginianae Schw.) 



Apple-cedar rust occurs in practically all apple-growing sec- 

 tions of the central and eastern United States. Diseased fruits 

 are only occasionally found on the market and even then the rust 

 is merely a slight blemish, since badly marked fruits are usually 

 culled out before shipment. The varieties most often affected are 

 York Imperial, Wealthy, Jonathan, Ben Davis, and Rome Beauty. 

 The rust fungus belongs to a large group of fungi that must 

 complete the different stages of their life cycle on different hosts. 

 The most common second, or alternate, host of apple-cedar rust" is 

 red cedar (Jiiniperus virginiana L.), on which the fungus pro- 

 duces the familiar rough, brownish galls known as cedar apples. 

 From these it spreads in the spring to apple leaves and young 

 fruits, but it must pass again to a red cedar if it is to continue 

 its development. 



Infection with the rust fungus takes place when the fruits are 

 young. It either causes the fruits to drop while still undeveloped 

 or stunts their development. They often become noticeably flat- 

 tened or otherwise malformed. 



Rust usually appears on the calyx end of an apple as grayish- 

 yellow to yellow spots (pi. 2, A) 3 that vary in superficial diameter 

 from about y 8 to % inch and extend into the flesh for Vi to % 

 inch or even to the core. The surface of the spots may be smooth, 

 or it may be roughened with the spore-producing bodies (aecia) of 

 the fungus, which are in the form of pimples or of open, cup- 

 shaped receptacles with flaring, papery edges. None of these 

 measure more than y 16 inch in diameter. The flesh beneath rust 

 spots is woody and usually greenish, though in the Winesap and 

 the Ben Davis the green is sometimes intermixed with a pro- 

 nounced brown. 



The disease can be controlled by spraying or by removing all 

 red cedars in the neighborhood of an orchard. The spray schedule 

 followed should be that recommended by the local agricultural 

 experiment station. It has been found necessary to eradicate 

 cedars to a distance of 1% to 2 miles from an orchard for satis- 

 factory control without spraying. 



(See 57, 65, 88, 114, 129.) 



Quince rust (Gymnosporangium clavipes Cke. & Pk.) produces 

 swellings rather than galls on red cedar. It has been known to 



3 Fruit shown in plate 2, A, is affected also with scald, which appeared 

 after fruit was removed from storage. 



