500 Journal of the Department op Agriculture. 



elsenburg, mulders vlei. 



Codling-inolh and Red Scale (Jonirol Invest ijjalidvs. — The follow- 

 ing- iiotos by Dr. Pette.y, Lecturer in Enloniolog-y, aic ])u1)lisli('(l as 

 a preliminary report on tlie 1920-191^1 season : — 



1. Powder dnstiiin' wjtli a niixiuic of 15 Ih. lead aisciiale jjowdcr 

 in 85 lb. fine lime versus a liquid S])iay of ''2\ 11). paste lead aisciiai;' 

 and 40 imperial gallons of water, in the contvol of codling-moth. 



Detailed records show that six a])])li(atioiis of dusted powder in 

 comparison with six applications of liquid on Kieffers resulted in 70 

 per cent, clean, fruit in the dusted area, and 92 per ceiit. clean fruit 

 in the sprayed area. Dusted Beurre Hardy pears produced 00 per 

 cent, non-infested fruit in comparison with 89.3 per cent, nom 

 infested in the liquid-sprayed trees. As the lime used in the dusting- 

 operations was of {^outli African manufacture of a poorer quality in 

 respect to texture and weight than that used in North America, where 

 dusting in many cases has been successful on apples, the writer will 

 not be satisfied that dusting of pear trees has been given every oppor- 

 tunity to demonstrate its success until imported special dusti ig lime 

 has been tried. 



2. South African manufactured ])aste and ])o\\(lcr lead arsenate 

 versus two reliable imported brands. 



The local manufactured paste and i)owder were both found to be 

 fully as satisfactory in every respect as the imported lead arsenates. 

 This should be of interest to fruit growers, as the former products 

 may probably always be purchased more cheaply than the imi)orted. 

 Powder lead arsenate is quite as efficient as the paste, and has the 

 special advantages over paste of not drying out, of being more quickly 

 mixed with water, and more chea])ly transported. 



'•\. Calcium arsenate powder versus lead arsenate ])aste and 

 powder in the control of codling-moth. 



Duchesse and Kieffer trees sprayed with a mixture of f lb. 

 cahuum arsenate powder, 3 lb. stone lime, and 40 gallons of water 

 produced respectively 73 per cent, and 67 per cent, clean fruit in 

 comparison Avith 93 per cent, and 91 per cent, non-infested for the 

 lead arsenate sprayed trees. It appears that calcium arsenate, a 

 (■om])aratively new insecticide, wdiicli is considerably cheaper than 

 l(>ad arsenate, and is reported to be efficient in the control of codling- 

 moth, especially in Canada, Nova Scotia, and Oregon, is a failure 

 under South African conditions. Tt may, however, improve the 

 efficiency by strengthening the solution, but much increase in strength 

 would make the difference in cost between the two insecticides so little 

 that its substitution for lead arsenate would certainly be inadvisable. 



4. The influence of bordeaux on tln^ efficiency of lead aisenate 

 in the control of codling-moth. 



Kieffer and Beurre Hardy trees sprayed in the two first codling 

 ajjplications with 21 lb. lead arsenate paste in 40 gallons bordeaux 

 mixture (4-4-40) produced 88.3 per cent, and 8.3.1 per cent, non- 

 infested fruit respectively in comparison with 91.9 per cent, and 89.3 

 per cent, clean fruit for the trees where water was substituted for 

 bordeaux mixture. This indicates that lutrdeaux destroys somewhat, 



