200 EXPERIMENT STATION. [Jan. 



termined for different kinds of plants at different ages. This 

 has accordingly been made a subject of particular investiga- 

 tion during the past year. 



Tomatoes were the first crop tested, the usual greenhouse 

 varieties being seleclod ; and the plants were fumigated at all 

 stages of growth and under varying conditions, to determine 

 in each case the maximum amount of gas which could be 

 used without injury. These experiments have now been com- 

 pleted, and demonstrate that it is possible to fumigate tomatoes 

 with a sufficient strength of cyanide to destroy the white fly 

 without injuring the plants, provided certain conditions are 

 carefully observed. • The information thus obtained has 

 already been supplied to a number of persons who have 

 had trouble with the white fly in their greenhouses, and 

 has been used successfully, and a bulletin on the subject 

 is now being prepared. At the present time a similar series 

 of experiments with cucumbers, another important forcing- 

 house crop, and one also seriously injured by the white fly, 

 is in progress. 



The prevalence of root ir.aggots of various kinds during 

 the past few years has called attention to the need of a more 

 thorough study of the methods for controlling these insects; 

 and a series of tests of these methods was begun last spring, 

 the intention being to try different treatments recommended, 

 and obtain evidence as to their comparative value. For vari- 

 ous reasons, however, it was impossible to complete these 

 experiments during the season, and it is planned to repeat 

 them on a larger scale next year. 



The last two summers have been unusually favorable for 

 the rapid increase and distribution of the San Jose scale. 

 This pest has been in Massachusetts for about fifteen years, 

 and in the localities where it was first introduced has spread 

 in all directions for some distance. New centers of infesta- 

 tion, however, have been constantly established from the 

 planting of infested stock of one kind or another ; and while 

 five years ago most of these centers were already in existence, 

 the number of scales at each was so small that their presence 

 was generally unsuspected. It would seem that during the 

 first two or three years in any locality this scale spreads but 



