07 



moreover, (here is the additional danger of infection from the 

 spores of Diaporthc i><ir<ixllica. In order to reduce the chances 

 of infection from wood rotting and other fungi, it has been the 

 prevailing custom for many years in this country as well as 

 abroad, to paint all exposed surfaces of wood Avith tar or lead 

 paint. Judging from our own experience perhaps these are as 

 good general preparations for this purpose as any that we care 

 to recommend at this time, though they are not ideal and they 

 do not prevent the checking of the wood. Morever, they must 

 be renewed from time to time in order to accomplish permanent 

 good. < 1 reosote is excellent for a preliminary coating, but it 

 sinks into the wood readily and apparently has waterproof quali- 

 ties of only temporary value. It should always be followed 

 (within a few days, for example) with some thick or heavy coat- 

 ing, such as tar or paint. 



For preventing the drying back of the cambium layer at the 

 edge of a cut, we have so far found nothing better than orange 

 shellac. This does not long remain a waterproof covering under 

 ordinary conditions, and should, as in the case of creosote, be 

 covered with a heavy coating of paint or tar, say within. two or 

 three weeks after it is applied. Many other preparations for 

 covering exposed wood have been tried, but those mentioned ap- 

 pear to have been the most satisfactory from the point of view 

 of our experiments on ornamental and orchard chestnut trees. 



(4). Sanitation. 



In cutting out diseased spots in the trunk or branches of 

 chestnut trees, the chips should be carefully gathered in papers, 

 or better, paper bags, and destroyed by burning. They should 

 not be left scattered about on the ground. In other w r ords, sani- 

 tation is one of the essentials for success in this kind of work, 

 just as it is in the case of diseases of human beings. In all of 

 our experiments with the disease on one particular plot the 

 chips were left where they fell. No attempt was made to de- 

 stroy them. Later many of these chips were examined and ap- 

 parently good, though dormant, fruiting pustules were present in 

 the majority of cases. To take one particular case: In March, 

 1911, some diseased spots, with good fruiting pustules, were cut 

 from a chestnut tree and the chips left on the ground in a sunny 

 exposed place on a dry hill- top. These remained on the ground 



