622 



of the liquid, which is important in covering the cyanide when a small 

 dosage is used. For sodium cyanide, the proper proportions for 

 securing the maximum amount of gas are as follows : — sodium cyanide, 



1 oz. avoirdupois ; sulphuric acid, 66° Be., 1| fluid oz. (U.S.) ; water, 



2 fluid oz. (U.S.). The dosage tables are based on this formula and 

 vessels are provided which are properly gi-aduated for it. With these 

 vessels, if a tree requires 12 oz. of cyanide, the acid pitcher is filled to 

 the 12 mark with acid and the water pitcher to the 12 mark with water. 

 A fumigating outfit of 30 tents operated by five men can treat about 

 400 trees a night. The cost per tree varies from lOd. to 6s. 3d., the 

 average being between Is. Ojd. and Is. 3d. A portable generating 

 machine is now commercially obtainable. Only a minute or two is 

 required for producing the gas. Other advantages are : accuracy 

 of dosage, economy of material, cleanliness of manipulation, one man 

 less required, and freedom from acid burns on the tents. The 

 machine is mounted on two wheels. It consists of a central barrel- 

 like drum, which encloses a smaller vessel in which the generation of 

 gas takes place. To one side, and above this, is a vessel containing 

 the cyanide which is dissolved in the required amount of water. On 

 the other side is another vessel which contains the acid. The cyanide 

 solution and the acid are conducted into separate graduated glass 

 cy finders for the dosage and then directed together into the generating 

 vessel. As this is within a larger vessel, the only outlet is through a 

 rubber tube, which conducts the gas under the tented tree. A new 

 portable generating machine of dift'erent construction, and working 

 on somewhat different principles, is also illustrated, but not described, 

 in this paper. Though spraying is not recommended for citrus scale- 

 insects, this method is dealt with at length and several formulae are 

 given, kerosene and distillate emulsions being preferred [see below]. 

 Spraying is now very generally used throughout the citrus belt for 

 the control ot red spiders and mites, an alternative treatment being 

 provided by the application of dry sulphur, the cost of which is about 

 one- half that of spraying. In spraying, commercial lime-sulphur is- 

 now very generally used : commercial lime-sulphur, 4 or 5 gals., and 

 water, 200 gals. Some growers add flour paste to ensure enhanced 

 spreading and adhesion properties. From 6 to 8 lb. of flour are mixed 

 in as many gallons of water, the mixture is brought to the boil and 

 added to a 200-gallon tank of spray solution. The dry flour may also 

 be added to the spray. Where mites are especially persistent, it is- 

 desirable to add 15 or 20 lb. of dry sulphur to the commercial 

 fime-sulphur spray. 



The citrus pests recorded in this paper are : Saissetia oleae, Bern, 

 (black scale), Chrysomplialns auranlii. Mask., and C. aurantii var^ 

 citrinus, Coq. (red and yellow scales), Lepidosajjlies heckii, Newm. 

 (purple scale). Coccus citricola, Campb. (citricola scale), Coccus hes- 

 peridum (soft brown scale), Aspidiotus rapax, Comst. (greedy scale),, 

 Aspidiotus hederae, Comst. (oleander scale), Icerya purchasi. Mask, 

 (cottony cushion scale), Pseudococcus citri (citrus mealy bug), Telrany- 

 chus mytilaspidis, Riley (citrus red spider), Tetmnychus telarius, L. 

 {sexmaculatus, Riley), Eriophyes oleivorus (silver mite), Scirtothrips- 

 {Euthrips) citri, Moul. (citrus thrips), Tortrix citra>ia, Fern, (orange- 

 tortrix), Pardomorus {Aramigus) fidleri, Horn (Fuller's rose beetle), a 

 species of Diuhrotica and Aphids. 



