"tufts" of green leaves at ends of twigs. As the 

 disease progresses through the tree, Umbs die 

 back and each year more of the tree becomes 

 infected. Fruit on infected trees at first appear 

 normal, but they most often drop prematurely. 



Young trees infected with x-disease should 

 be removed and destroyed. In older trees, re- 

 moving infected Umbs may slow the spread of 

 the mycoplasmas; but once x-disease has 

 started, it is difficult to control. Antibiotic 

 therapy may help also. 



Removing chokecherries near peach or- 

 chards is essential. 



For additional information on any of these 

 pests, please refer to: 



Jones, A.L. 1976. Diseases of Tree Fruits. (Cooperative 

 Extension Services of the Northeast States. NE 96. 



LaRue, J.H. and RS. Johnson (eds.). 1989. Peaches, 

 Plums, and Nectarines: Growing and Handling for 

 Fresh Market. Cooperative Extension, University of 

 California. No. 331. 



Prokopy, R.J., P.J. Powers, D.R. Cooley, and J.W. 

 Gamble. 1991. Peaches, Pears, Plums - Pest Control 

 Guide for Commercial Growers in Southern New En- 

 gland. University of Massachusetts Cooperative Ex- 

 tension System Circular C-159 R 1991-2. 



^% •10 •i^ ^L0 ^|V 



#J% rfi rf» •Y* •?• 



Peach Pests IV: Diseases of 

 Peach Wood 



Karen I. Hauschild 



University of Massachusetts Cooperative Extension System 



This is the last in a series of four articles 

 describing major insect and disease pests of 

 peaches in Massachusetts. In this article I wiU 

 describe diseases that attack peach wood, pri- 

 marily canker diseases. 



In general canker diseases occur where 

 peach trees are stressed due to drought, poor 

 growing conditions, cold temperature, or poor 

 pruning. Healthy, vigorous trees are less sus- 

 ceptible to attack by canker diseases. Several 

 disease organisms cause canker formation on 

 peaches. Following are brief descriptions of the 

 major causal agents of perennial cankers found 

 on peaches and nectarines in Massachusetts 

 orchards. 



Cytospora (Valsa) Canker 



Two species oiCytospora are associated with 

 peach canker - C. leucostomia Saac. and C. 



cincta Saac. Cytospora overwinter in cankers or 

 on dead peach wood. Bumps containing pyc- 

 nidia with small conidia are produced under 

 bark. These pycnidia grow through the bark and 

 expose spores to rain. Splashing rain or rain 

 driven by heavy winds spread conidia to other 

 infection sites on damaged or injured bark. 

 Canker growth is related to temperature and 

 growth habit of the peach tree itself C. cincta is 

 most active during spring and fall at tempera- 

 tures between 60 and 75°F. C. leucostomia is 

 more active at temperatures between 86 and 

 91°F, that is, during the summer months. Can- 

 ker development can occur in one of three ways. 

 First, cankers may extend down limbs toward 

 tree trunks, with Umb death occiirring at the 

 rate of one or two Umbs per year over a period of 

 several years until the entire tree eventually is 

 killed. This pattern is the classic "perennial 



Fruit Notes, Winter, 1993 



