176 fJoUKWAL 01<' THE I)EJt*AIlTMl!-M OF AoHKJL J.l UKE. AuU., 1922. 



THE CONTROL OF CODLING-MOTH IN PEARS 

 IN SOUTH AFRICA. 



Dusting versus Liquid Spraying. 



By F. W. Pettey, B.A., Ph.D., Entomologist, Klsenbuig' Scliool ol 

 Ao'riciilture and Experiment Station, Muldei-s Ylei. 



Introditction. 



The advantages of power dusting, when it is successful, are (a) 

 rapidity of application, since dust may be applied 5 to 10 times 

 more rapidly than liquid, (h) saving of labour, as it requires only 

 two men, i.e. a driver and a manipulator, and (c) a comparatively 

 lighter outfit than a spray equipment, which enables the fruit grower 

 to work on steep hillsides or on low-lying ground immediately after 

 a rain. 



Under Cape Province conditions it would have the advantage of 

 enabling the fruit grower himself to apply the material to his trees, 

 and early in the morning before the severe south-east wind interferes 

 with operations. In dusting, there is no water supply problem, a 

 decided advantage in manj' parts of South Africa, where orchards are 

 on steep hillsides and where water is often scarce. The greatest 

 disadvantages are the greater cost of material, and especially the 

 inefficiency of dusting for the control of scale insects and other suck- 

 ing insects, and peach leaf curl. Consequently, at the present state 

 of dusting efficiency, an outfit for this purpose could only be a supple- 

 ment to the spray machine. A power duster, were it successful, would 

 be of the greatest advantage to the large fruit grower in enabling 

 him to apply the insecticide to his trees in the required time, with 

 practically five times less spray machinery. Comparatively cheaper 

 hxboair and more expensive lime in South Africa tend to minimijje 

 the advantages of the dusting method of control. 



In 1918 the writer considered that improved power dusting for 

 the control of orchard pests had developed to such an extent in 

 Canada and the United States that the time for giving it an exhaus- 

 tive trial in South Africa had arrived (1). Through the enthusiastic 

 support of the Chief of the Division of Entomology <;C. P. Louns- 

 bury), suitable machinery was procured, and experiments Avere under- 

 taken, based on the materials and methods reported to be successful in 

 the control of codling-moth and scab in apples in North America. 

 Mr. Lounsbury, in a letter to the writer in 1918. wrote : " I imported 

 a Jumbo duster into South Africa when the dust craze struck the 

 Ozark region about fifteen years ago, and some work was done with it 

 at Meerlust." At that time, however, dust materials and machinery- 

 were far from satisfactory. The paris green and lime were much too 

 coarse, and the machinery- was not well adapted for dusting. 



Ackerman. in the California Bvlleti7i, Department of Agricul- 

 ture, Vol. \1, No. 1, 1922, is Iho only scientist who hns ])nblishe(| 



