SELECTING THE TREES 35 



define all of them in this brief space. In gen- 

 eral one should watch for any dead areas on 

 the bark. Apple diseases will show themselves 

 in the form of "cankers" — which are simply 

 more or less circumscribed areas of dead and 

 usually sunken tissue. Crown gall is a disease 

 that attacks the roots, forming unsightly warty 

 excrescences usually just at or below the soil 

 line. No reputable nursery will sell stock so 

 infested (it is against the law anyhow). 



Crown gall should not be confused with an- 

 other gall-producing pest, the woolly aphis. 

 This is a plant louse, covered with white wool, 

 which causes small galls on both the roots and 

 on the trunk and branches of the tree. 



Nurserymen have long contended that neither 

 the woolly aphis nor the crown gall was injuri- 

 ous to trees. To prove it they have in the past 

 planted orchards using only infested and in- 

 fected trees. They claim these orchards are a 

 success. Maybe so. However, I wish they 

 would tell me what is the matter with a few 

 trees we have. I know the trees have crown 

 gall, but I can't find anything else wrong — still 

 they have failed to grow or to bear as have 

 healthy trees on the same soil and with the 

 same treatment. I am inclined to think that 

 the nurserymen who made the claim are mis- 

 taken. At any rate I plant no trees bearing 

 either of these pests — not if I know it. 



