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How Perennial Teach Cankers Develop 



The spores of the peach canker fungi are released during 

 March, April and May and, sometimes, in early June. Most cankers 

 originate from infections that take place during late March, April 

 and May, although a second wave of infections take place during Oct- 

 ober and November. Depending on the locality and the prevailing 

 weather conditions within each year, these periods may be longer 

 or shorter, but it is evident that infections take place during the 

 cool months of the year, although, presumably, spores are present 

 throughout the year. Both the low winter temperatures and the 

 high temperatures of the summer months seem to effectively inhibit 

 initiation of new infections. 



Even when the temperature is favorable, spores can cause in- 

 fection only when they land on injured or dead bark. The most 

 common point of entry of the fungus, especially in young trees, 

 seems to be unhealed pruning wounds and stubs. This is followed, 

 in order of lesser importance, by fruit spurs or pedicels, terminal 

 dieback, dead buds, winter injury, mechanical injury, lenticels, 

 leaf scars, insect borers, etc. Extreme winter cold seems to be the 

 most important factor in predisposing peach trees to perenni al can- 

 ker through resulting injuries to peach trees, such as bud killing 

 and dieback of twigs. 



