WALNUT BLIGHT IN THE EASTERN UNITED STATES. 5 



inoculation by needle puncture and two inoculated twigs having 

 characteristic cankers. The control, which was punctured with a 

 sterile needle, is shown at the right. The needle punctures in the con- 

 trolbarely showed at this time, 30 days after inoculation. 



Subsequently the organism was reisolated from a number of these 

 inoculated nuts, and the cultural studies so far made from these 

 isolations coincide with those made by Smith 1 and by Pierce. 2 



TIME OF INFECTION. 



During the season of 1916 infection apparently took place about 

 the last of May in the cases under observation. At this time the 

 nuts were very well developed, approximately three-fourths to 1 

 inch in diameter, and although there was a slow increase in the area 

 of the infection points through July and some coalescing of these 

 spots to form larger ones, the disease did not begin to work 

 deeply into the tissues until about the middle of August, by which 

 time the shell had formed and hardened. By the end of the 

 season the husks had become black, watery, and rotten, staining 

 the shells and clinging to them when allowed to dry. The develop- 

 ment of the nuts did not seem to be affected materially, if at all. 

 The growers interviewed were unanimous in stating that infection 

 was usually late and that no material shortage of crop resulted there- 

 from. However, the former part of this statement probably could 

 be applied only to the time at which the infection became so evident 

 as to attract the attention of ordinary observers. 



In the California orchards the greatest loss from infection occurs 

 at or near blooming time. Infection is serious in proportion as the 

 weather is moist at that time. A dry, clear spring means little, if 

 any, blight, whereas serious infection is associated with moist, foggy 

 spring weather. The disease as observed in 1916 in Pennsylvania, 

 Delaware, and the District of Columbia resembled closely the severe 

 late infections described by Smith. 1 



CONTROL OF WALNUT BLIGHT. 



Various attempts to control this disease by spraying and by soil 

 applications have been made in California, and although some suc- 

 cess has attended the spraying experiments it has not been of such 

 degree as to extend any material encouragement to the commercial 

 orchardist. That spraying will be of no value under eastern condi- 

 tions can not be assumed from this fact, however, owing to the dif- 

 ference in the infection periods previously referred to. Neverther 

 less, spraying to control diseases of bacterial origin has never been 



11 Smith, K. E., Smith, C. O., and Ramsey, H, J. Op. cit * Pierce, N. B. Op. cit 



