352 PEAR GROWING IN CALIFORNIA. 



branches. The surgeon who would perform an amputation without 

 thoroughly disinfecting his instruments before the operation would 

 be considered criminally negligent. While the life of a tree is of 

 much less importance than that of a human being and the same degree 

 of criminal negligence could not be charged against the blight cutter 

 who fails to disinfect his tools, nevertheless he is subjecting the tree 

 to grave dangers comparable to those of the patient of the negligent 

 surgeon. 



Corrosive Sublimate. 



The best all-round disinfectant for this work is corrosive sublimate 

 (bichloride of mercury) in a 1 to 1,000 solution. It is prepared in 

 the form of tablets, one of which dissolved in a pint of warm water 

 gives the desired dilution. The liquid should be carried in bottles 

 or glass jars and not metal containers. Neither should tools be dipped 

 in the liquid as a chemical reaction takes place rendering its use as a 

 disinfectant ineffective. The common method of application is by 

 means of a swab made by wrapping a piece of cloth and securely tying 

 it around the end of a stick. By means of this swab, which may be 

 carried in the liquid, saws, shears and cut surfaces may be quickly 

 treated with the disinfectant. It is well to practice the disinfection of 

 all cuts as well as the disinfection of the tools. This is, of course, very 

 necessary when large areas of bark are being removed from the trunks 

 and larger branches. In such cases it is not important that tools be 

 disinfected until a separate infection is worked on, but it is exceedingly 

 important that the entire surface of such cut surfaces be thoroughly 

 treated with the disinfectant as soon as the bark has been removed. 



Corrosive sublimate is very poisonous and the solution should not be 

 left where children might get it, nor where chickens or other animals 

 might take a drink. It will do no injury by external contact with the 

 skin but is exceedingly poisonous when taken internally. 



RESISTANT ROOTS. 



While careful attention to the details outlined regarding the cutting 

 method in pear blight control has resulted in the saving of thousands 

 of trees in California, there are those who have given up the fight 

 and the neglected orchards have either been destroyed or rendered 

 unprofitable. Both those who have carried on the fight successfully 

 and those who have given it up as hopeless will welcome anything which 

 will prevent or render easier the expensive and exceedingly difficult 

 control methods now in use. For some time it has been known that 

 certain species and varieties were more resistant to pear blight than 

 others. For example, the Japanese or Asiatic Pear (Pyrus serotina), 

 is not so susceptible as the French or European species (Pyrus 

 communis) . Most of the older orchards in California have Pyrus 

 communis roots and these have been readily affected by the blight. 

 The resistance of the Japanese stock has made it popular of late and 

 whereas practically 100 per cent of the pear trees propagated by 

 California nurserymen four years ago were on European root stock 

 at least 75 per cent are now on Asiatic roots and the effect in lessening 

 the root form of the disease will be very apparent as the new orchards 

 come into bearing. Blight in the tops of susceptible varieties such as 



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