GREENHOUSE PUMTOATION WITH HYDROCVANIC-ACTD GAS. H 



bugs, millipedes, etc., are somctiiues brought in with packages, or they 

 may crawl into the greenhouse through small openings. 



COST OF HYDROCYANIC-ACID GAS FUMIGATION. 



The economy in the use of hydrocyanic-acid gas as a means of con- 

 trolling apliids, wliite flies, thrips, and the common greenhouse scale 

 insects is apparent from the following figures, which are based on 

 current manufacturers' prices : 



For the most part, aphids can be controlled with a single fumigation 

 at the rate of one-half ounce per 1,000 cubic feet at a cost of ap- 

 proximately 1 cent per 1,000 cubic feet. Tobacco fumigation with 

 standard tobacco paper costs from IJ to 3 cents per 1,000 cubic 

 feet, and to secure a satisfactory control the operation must be 

 repeated several times. Standard nicotine soap solution costs from 

 1 to 3 cents per gallon, and 4 gallons are required to cover plants 

 which would occupy 1,000 cubic feet of space. 



The greenhouse white fly can be controlled with three successive 

 fumigations at the rate of one-half ounce of sodium cyanid per 1,000 

 cubic feet, with a total cost of 3 cents per 1,000 cubic feet for a com- 

 plete control. Standard insecticides cost about 6 cents per 1,000 

 cubic feet for a single apphcation, and fully four appHcations are 

 required for a satisfactory control. 



Thrips can be controlled on such plants as azaleas, lihes, and ferns 

 with a single fumigation at the rate of one-half ounce of sodium 

 cyanid per 1,000 cubic feet at a cost of 1 cent per 1,000 cubic feet. A 

 single apphcation of nicotine soap solution costs fidly five times as 

 much as the gas treatment and stiU gives only a partial control. 



The common scale insects of greenhouses (excepting mealybugs) 

 can be controlled by fumigating the infested plants at the rate of 

 three-fourths ounce of sodium cyanid per 1,000 cubic feet at a cost of 

 1^ cents per 1,000 cubic feet. The standard proprietary insecticides 

 commonly recommended for scale insects cost approximately 4 cents 

 per gallon, with an average cost of 16 cents per 1,000 cubic feet for 

 each treatment. A 5 per cent homemade kerosene emulsion costs ap- 

 proximately one-half cent more per 1,000 cubic feet than does the 

 gassing method, and gives very indifferent results. 



The foregoing figures do not take into consideration the cost of 

 labor. Tlie time required for fumigation, howeyer, will not exceed 

 the time required for the mixing and ap])lication of the sprays. 



PRECAUTIONS. 



Do not guess the amount of chemicals to bo employed or the cu1)ic 

 contents of the house. 



Do not fumigate plants in a greenhouse in daylight. (For box 

 fumigation in daytune, see page 10.) 



