Cankers Due to Frost 305 



peaches, frost cankers, according to Jehle, "are oftenest 

 found on the main trunk of the tree, usually near the sur- 

 face of the ground or at the snow line of the previous 

 winter; in the crotches of the larger branches; or about 

 pruned stubs. They appear after a hard winter, particu- 

 larly one of extreme changes in temperature and more 

 particularly when such a winter follows a very late grow- 

 ing season. The cankers appear in the spring as slight 

 depressions. These are made more apparent as the tree 

 puts on new growth of wood over the area not affected. 

 Gum pockets usually form under the flattened areas and 

 the gum often oozes out during periods of wet weather. 

 The injured area is usually rather indefinite about the 

 margin, and the formation of a healthy roll of callus is 

 thereby much retarded. Fermentation of the dead tissue 

 occurs and various fungi and insects quickly follow. One 

 fungus, Valsa leucostoma, comes in so commonly that some- 

 times it has been regarded as the cause of the trouble." 



As to prevention: "It is impossible to predict the char- 

 acter of the winters, but one can judge by the growth and 

 maturation of the wood what the probabilities are that a 

 tree is in good condition to withstand a severe winter. 

 Soft, poorly matured wood is easily injured. The use of 

 highly nitrogenous fertilizers, particularly their use too 

 late in the season, is to be avoided. In seasons of drought 

 followed by abundant autumn rains a second growth is 

 not uncommon. This may be prevented or held to a suita- 

 ble minimum by the use of cover-crops." 



The treatment for frost cankers is the same as that for 

 other similar wounds, as advised on a preceding page 

 (page 296). It is difficult for the grower in some cases to 

 distinguish between frost cankers and those produced by 

 infection, and the subject also requires further investigation. 



