214 EXPERIMENT STATION. [Jan. 



FUMIGATION DOSAGE. 



I. TOMATOES. 



BY W. V, TOWER, B.S. 



Introduction. 



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 than 

 ordinarily destructive. The most important of these enemies 

 are the greenhouse white fly (Aleyrodes vaporariorum West.) 

 and thrips, and as these are most successfull}^ controlled by 

 fumigation with hydrocyanic acid gas, this treatment should be 

 familiar to tomato growers. Unfortunately, however, this is not 

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

 that when the gas is generated in sufficient quantity to destroy 

 the insects it will also injure the plants. 



The amount of hydrocyanic acid gas to which tomato plants 

 can be exposed without injury, under varying conditions of 

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

 investigated, so that there has hitherto been some reason for 

 this fear. To determine, therefore, just what tomato plants 

 ('(»ii1d withstand in the way of treatment, under all conditions 

 likely to be met with in commercial work, the experiments 

 which follow were planned by the writer and were carried out 

 ill the greenhouse of the dopartnient of entomology of the IMassa- 

 chiisetts Agricultural Experiment Station during the winter of 

 1005-06, by Mr. ^Y. Y. Tower, then a graduate student in en- 

 t(Uiiology at the Massachusetts Agricultural Coll(>ge. The ex- 

 ])('riiii('iils had just been C()m])let(Hl wh(>ii IMr. Tower accepted an 

 apj)oiiitmei!t in Puerto Ivico and was obliged to leave before the 



