200 EXPP:RIMENT station. [Jan. 



termined for different kinds of plants at diiferent 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 selected ; and the plants were fumigated at all 

 stages of growth and under varying conditions, to determine 

 in each case the maxiirium amount of gas which could Ix; 

 used without injuiy. Thcise 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 iufoi'niation thus obtained has 

 already boon supplied to a uuiiibci' of persons who have 

 luid trouble with the white lly in tlusir 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 cucumlxa's, another imj)ortant forcing- 

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

 is in progress. 



The prevalence of root maggots 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 s])ring, 

 the intention being to try different treatments recommended, 

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

 ous I'oasons, however, it was impossible to complete these 

 experiments during the season, and it is })lanned to repeat 

 them on a larger scale next year. 



The last two suunuers 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, l^ew 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 localily this scale spreads but 



