GREENHOUSE FUMIGATION WITH HYDROCYANIC-ACID GAS. 7 



that do not contain roses, rose geraniums, asparagus ferns, lemon ver- 

 benas, snapdragons, wanderbig Jew, or sweet peas can be fumigated 

 with safety with an initial dosage of one-half omico of sodium cyanid 

 (NaCN) per 1,000 cubic feet. In case there is any doubt as to the 

 amount of gas a 'plant mill stand without injury, it is preferaUe thai 

 the initial dosage he not over one-fourth ounce of sodium cyanid per 

 1,000 cubic feet and increased with subsequent fumigations until 

 the fatal point for the pest to be controlled is reached, it being borne 

 in mmd that in some mstances it is not possible to effect an abso- 

 lute control of all stages of some msects with one fiunigation with- 

 out injury to foliage or growing parts of certain plants. For ex- 

 ample, the greenhouse white fly can be eradicated with three suc- 

 cessive fmnigations at intervals of seven to nine days, usmg one-half 

 omice "f sodiimi cyanid (NaCN) per 1,000 cubic feet, m houses con- 

 taining such susceptible plants as colons, ageratum, heliotrope, fuchsia, 

 etc., with no injury to the fohage. Moreover, such resistant pests as 

 scale insects can be elimmated entirely by killmg the inunature 

 stages with a small dosage repeated at frequent mtervals. 



To determme the total amount of cyanid to be used, ascertain from 

 Table II on page 13 the plants in your greenhouse which are most 

 easily injured by the gas fumes and note the amount of cyanid 

 which was used per 1 ,000 cubic feet with little or no injury to the 

 plants. Then multiply the number of thousand cubic feet contained 

 in the greenhouse by the amount of cyanid to be used per 1 ,000 cubic 

 feet. For example, if one-half omice of cyanid is to be used per 1,000 

 cubic feet, and the greenhouse contains 15,000 cubic feet, the total 

 amount of cyanid necessary would be 7^ ounces. 



In case there is any doubt as to the amount of gas the plant can 

 stand without mjury, the uiitial dosage, as previously stated, should 

 not exceed one-fourth ounce per 1,000 cubic feet. 



Table I gives the amount of sodimn cyanid per 1,000 cubic feet 

 needed to destroy the bisect pests most commonly fomid in green- 

 houses. Before fumigation is begun, however, Table II should he 

 consulted for information as to the maximum dosage the particular plants 

 can stand without injury. If this dosage is less than that indicated in 

 Table I, complete control, of course, should not he attempted with one 

 fumigation 



