84 PROTECTION OF PLANTS. 1916-17 



Station has enjoyed from the very beginning the whole-hearted co-operation 

 and support of the fruit-growers of the district. "Go in and help yourself," 

 is the constant and typical response to our needs. 



It is not possible here to give a detailed statement of the various pro- 

 blems which have engaged attention in the course of the four years during 

 which the station has been opened, but mention is made of some few of 

 these in which definite and useful results have been obtained. Owing to 

 lack of time and equipment many interesting problems have had to be 

 given up temporarily, while others are still incomplete. It ife hoped that 

 when conditions become more settled, and more assistance is available, all 

 these deferred questions will once more be taken up. 



Mosaic Disease of Tomatoes 



Yearly surveys have shown that this disease is present in from 1 to 3% 

 of all the plants grown in the district. Experiments have shown that the 

 loss in crop in plants affected by the disease is as high as 40%. Where the 

 disease is present to an excessive extent it has been found that it is usually 

 carried over from the previous year in the seed bed, and that changing the 

 earth in this seed bed will eliminate the disease readily. It is apparently not 

 carried in the seed. 



The Currant Polyporus 



This fungus was found on only one currant plantation in the peninsula 

 but it was present in about S3% of the plants in this case. It was not found 

 to be a serious parasite, apparently drawing on its host for water supply 

 mainly. Experiments were carried out to determine whether it could be 

 checked or destroyed by means of chemicals. Formalin and copper sul- 

 phate were found to be promisingly useful, but final data on the value of 

 these could not be obtained owing to the unavoidable removal of the 

 plantation. 



Peach Yellows 



Considerable work on this disease has shown clearly that when a 

 diseased tree is severely pruned or "dehorned", the growth of the succeeding 

 year is almost without exception perfectly normal in appearance. This 

 apparent restoration to health may last for two or even three seasons, but 

 in the end all such trees develop the disease again. The question of the 

 danger of using pits from diseased trees for the production of nursery stock 

 was also investigated. Out of 1,200 pits collected from five diseased trees 

 8% grew and produced during the first year normal seedlings. Eleven of 

 these seedlings showed disease at the end of the.second year, however. 



