Methods of Control 387 



Table 21 is used per 1,000 cubic feet of space, and if 

 the greenhouse to be fumigated contains 1 5,000 cubic 

 feet, then multiply the number of cubic feet con- 

 tained in the greenhouse by the amount of cyanid 

 to be used per 1,000 cubic feet, 1,500 times 

 equals 7.5 ounces cyanid. If there is the least doubt 

 as to the amount of gas the plant can stand without 

 injury the initial dose should not exceed one-fourth 

 ounce for each 1,000 cubic feet of house space. 



Table 20 



Amounts of Cyanid and Number of Fumigations 

 Sufficient to Destroy Various Greenhouse Pests 





Ounces per 



Number of 



Interval] 



Insects 



1,000 Cubic 



Fumigations 



Between 





Feet 



Required 



Fumigations 









Days 





y2 



I 







HI 



I 





Thrips 





2 



10 







3 



7 to 9 



Long scale 





I 





**Greenhouse orthezia .... 





2 



21 to 28 







I 







2^ 



I 





**Long-tailed mealybug . . . 





2 



do. 





2y. 



2 



do. 







2 



do. 





2y2 



2 



do. 







2 



do. 





2y 



2 



do. 



Tessellated scale 



2>^ 



2 



do. 



Florida fern caterpillar .... 



5 



I 







5 



2 



do. 



*For the most part aphids can 'be controlled with one-half ounce 

 of sodium cyanid per 1,000 cubic feet, although there are a few 

 species which are quite resistant to this gas and not so readily killed. 



fThe greenhouse Orthezia and mealybugs around the roots of 

 plants are very difficult to kill, and this dosage is recommended only 

 for those occurring above the soil. 



