6 Donald Reddick and V. B. Stewart 



The crown-gall disease seems to have been much more prevalent in 

 New York some fifteen or twenty years ago than it is at the present time. 

 There was much more agitation about the disease at that time, but this 

 may be accounted for in part by the fact that inspection service for San 

 Jose scale was being instituted and enforced, and that this inspection 

 involved also examination for and rejection of trees having crown-gall. 

 Aside from this, however, one of the writers (S), who was interested in 

 diseases of nursery trees, recalls that in 1909 the fields in one large nursery 

 from which apple trees had been dug were thickly strewn with trees 

 that had been rejected at digging time because of crown-gall.' It was 

 this condition, in part, that led to the experiments herein reported. But 

 in 1910, when trees were sought for the experiments, very few were to be 

 found and there was some difficulty in procuring the necessary stock. 

 This condition has prevailed in subsequent years. One factor in nursery 

 management may have contributed to this desirable condition, namely, 

 that there has been an increasing tendency on the part of the nurserymen 

 to grow trees in rotation with farm crops, thus allowing for the death of 

 Bacterium tumefaciens in the soil or on plant parts. Another factor 

 which may be involved is that most apple trees in New York are budded ■ 

 on French stock. One of the writers (S)^ has expressed the opinion that ' 

 French-grown stock is less susceptible to crown-gall than is American- 

 grown stock, and it seems obvious that the practice of budding in the field, 

 which is the common practice in New York, gives less opportunity for 

 widespread infection than does that of bench grafting. 



f 



PLAN OF THE CROWN-GALL i:XPERIMENT 



In order to determine, if possible, the importance of crown-gall on j 

 apple and peach trees under the conditions existing at Ithaca, New York, 

 an experiment was planned, the details of which were as follows: 



The land for the experiment lay in a low field which had been in grass 

 for a number of years previously. There are hills on all sides, but there 

 is suitable drainage so that the soil is never too wet for good growth. The ; 

 soil is a good loam, running out into stony loam on the side where the rows > 

 are marked A in figure 1. The soil is suitable for the growth of both 

 apples and peaches, but the location is unsuited for peaches. Peaches 

 are grown successfully a few miles from Ithaca, but there is little chance 

 of securing crops in the immediate vicinity, chiefly because of low temper- 

 ature in the winter. This was not fully realized at the beginning of the 

 experiment. 



The land was ploughed and cultivated each year and a sown cover 

 crop usually was employed. 



' It is likely, though, that some of these trees bore galls produced by an aphis {Schizoneura lanigtra), . 

 and this is the opinion expressed by one large nurseryman. i 



• Stewart, V. B. Exclusion legislation and fruit tree production. Phytopath, 8:360-364. 1918. (The t 

 citation refers to page 362.) 



