CALIFORNIA CITRUS CULTURE. 69 



Lime and Sulphur. 



Even better than sulphur alone is hydrated lime and flowers of 

 sulphur mixed in equal parts and blown upon the trees with a power 

 machine, as is shown in Fig. 45. In the citrus orchards this is a very 

 important method of controlling the citrus red spider (Tetranychus 

 mytilaspidis) and the six-spotted or yellow mite (Tetranychus ~bimacu- 

 latus). 



TANGLEFOOT BANDS. 



To prevent insects from crawling up the trunks of trees and plants 

 sticky bands have been devised which have proven exceedingly success- 

 ful in many instances. 



Tree tanglefoot is a thick, sticky substance which, when applied as a 

 band, remains moist for several weeks and is a very effective barrier 

 against cankerworms, caterpillars, cutworms, Fuller's rose beetle and 

 other crawling insects. 



The material is put up in cans. It should be applied directly to the 

 trunk of the tree several feet above the ground. 



* FUMIGATION. 



Fumigation consists in the generation and uses of gases to kill destruc- 

 tive insect pests. Formerly such practices were limited to the uses of 

 carbon bisulfid, sulphur dioxid and tobacco fumes. The use of hydro- 

 cyanic acid gas in citrus orchards has lately been so perfected as to 

 become of very great importance, and has opened up a remarkable field 

 in the control of orchard pests. 



HYDROCYANIC ACID GAS. 



Hydrocyanic acid gas is generated by the addition of diluted sul- 

 phuric acid to sodium or potassium cyanide. The generation is made 

 in an earthenware jar, the gas being confined in a fumigation house, 

 or, if the work is being done in the orchard, in a tent thrown over the 

 tree. For many years the methods of fumigation depended entirely 

 upon each fumigator, there being no uniform or common procedure. 

 The results of this early work so clearly showed the need of systematism 



*Prom "Injurious and Beneficial Insects of California," The Monthly Bulletin of 

 the State Commission of Horticulture, Vol. II, Nos. 1 and 2, 1913. 



