512 



potassium base, while a better grade distillate was used. Two pro- 

 prietary miscible oils with sulphur combinations were tried, but no 

 sulphur combination gave more than 50 per cent, mortality, while 

 oil emulsions gave from 95 to 98 per cent. An emulsion containing 

 1 per cent, oil gave 100 per cent, mortality of the eggs. Some type of 

 spreader is necessarj^ for use with these emulsions ; lime-casein was 

 found impracticable as it combines with the soap and liberates the oil ; 

 casein and borax were fairly good, but with further investigation it is 

 hoped to obtain a better spreader. 



In no case has dusting with sulphur given good results ; it is necessary 

 to have the maximum temperature above 90° or a mean temperature 

 above 75° for this remedy to be effective against P. pilosus. 



QuAYLE (H. J.). Control of the Codling Moth in Walnuts.— Mi!%. 

 Bull. Cal. State Dept. Agric, Sacramento, xi, no. 7, July 1922, 

 pp. 40-43. 



The only satisfactory remedy against the codling moth [Cydia 

 pomonella, L.] in walnuts is to coat the nuts with some poison that will 

 destroy the larvae before they effect an entrance. Tests made in 1920 

 and 1921, in continuation of those already recorded [R.A .E., A, viii, 238], 

 show an undoubted superiority of spra5dng over dusting. The material 

 recommended is 6 lb. basic lead arsenate to 200 U.S. gals, water. 

 For dusting, 10 per cent, of lead arsenate seemed the best, with kaolin, 

 hydrated lime or refuse lime from beet-sugar factories as a carrier. For 

 the control of the walnut aphis, Chromaphis juglandicola, either alone 

 or with codling moth, the addition of Black-leaf 40 has been suggested 

 [R.A.E., A, X, 286]. The development of C. pomonella varies according 

 to the season, but, as a rule, treatment should be from about the last 

 week in May to the last week in June. The nuts should be as large 

 as possible at the time of spraying, though this is less important than the 

 condition of the calyx in the case of apples. 



Collins (C. F.). Control of Citricola Scale. — Mthly. Bull. Cal. State 

 Dept. Agric, Sacramento, xi, no. 7, July 1922, pp. 43-45. 



Fumigation with liquid hydrocyanic gas, as practised in California 

 against the citricola scale [Coccus citricola], is described. The process 

 is begun as soon as all the scales have hatched (about mid-July in 

 Tulare County), and usually continues until October. For two or three 

 weeks late in August the scale seems more than usually resistant, and 

 poorer results are obtained. The dose is generally 18 cc. until September, 

 when the weather becomes cooler, and 20 cc. is then used. Spraying 

 is still practised to some extent, but its cost is equal to that of fumiga- 

 tion, and the results are far less satisfactory. 



Armitage (H. M.). Biological Control with particular reference to 

 the Mealybug and Black-scale Work in Southern Cahfornia.— 



Mthly. Bull. Cal. State Dept. Agric, Sacramento, xi, no. 7, July 

 1922, pp. 45-50. 



The problem of biological control resolves itself into the production 

 of a controlled quantity of desirable natural enemies that can be liber- 

 ated with regard to the seasonal development of both enemy and 

 host at a cost that will permit this method to compete with commercial 

 remedies. The Coccinellid, Rhizohius [ventralis], or the Chalcid, Scutcllista 



