214 EXPERIMENT STATION. [Jan. 



FUxMIGATION DOSAGE. 



I. TOM atop: s. 



BY W. V. TOWER, B.S. 



BY H. T. FERNALD. 



Tomatoes are extensively grown in [Massachusetts in green- 

 houses. Unfortunately, they are subject to the attacks of sev- 

 eral kinds of insects which under glass seem to be more thau 

 ordinarily destructive. The most important of these enemies 

 are the greenhouse white fly (Aleyrodes vaporariorum West.) 

 and thrips, and as these are most successfully controlled by, 

 fumigation with hydrocyanic acid gas, this treatment should bt 

 familiar to tomato growers. Unfortunately, however, this is noi 

 the case, many growers seeming to be afraid to use it for feai 

 that when the gas is generated in sufficient quantity to destro;; 

 the insects it will also injure the plants. 



The amount of hydrocyanic acid gas to which tomato plant; 

 can be exposed without injury, under varying conditions o: 

 light, temperature, humidity, age, variety, etc., has never beer 

 investigated, so that there has hitherto been some reason fov 

 this fear. To determine, therefore, just what tomato plant; 

 could withstand in the way of treatment, under all condition; 

 likely to be met with in commercial work, the experiment; 

 which follow were planned by the writer and were carried ou 

 in the greenhouse of the department of entomology of the Massa 

 chusetts Agricultural Experiment Station during the winter o: 

 11)05-00, by Mr. W. V. Tower, then a graduate student in en 

 tomology at the [Massachusetts Agricultural College. The ex 

 periments had just been completed when Mr. Tower accepted ai 

 appointment in Puerto Rico and was obliged to leave before th. 



