8()() JoiRNAI. OF THE DkPAKTMENT OF AgIUCULTUEE. OcT., 1922. 



ARSENICA.L SPRAY EXPERIMENTS FOR CON- 

 TROLLING CODLING-MOTH IN PEARS AT 

 ELSENBURG. 



By F. W. Pettey, Pli.])., Entomologist, Elseiilnirjo- School of 

 Agriniltiiro and pjxpeiiiiiciit Station, Mulders Yloi, Cape. 



TK'ruonnrTTON. 



ExPEKlMKNi'S in llic coiiliol ol ('odliiif^-nioth Uuvr Ix'cii iii ])rog'i'ess 

 sevejal years for considering (a) tlic pjiul i(;d)ilily o'i siihsti luting 

 power dusting for sj)iaying in the control of codling-niotli, (h) the 

 advisability of substituting (ialciuni arsenate, a cheaper ursenical, for 

 lead arsenate, in the control of this pest, (c) the more effective control 

 of codling-moth by the addition of a calcium caseinate spreader to the 

 lead arsenate and water mixture, and {d) the influence of lime-sulphui- 

 and bordeaux mixture on the efficiency of lead j'.rsenate in the control 

 of this insect. The expei-iments concerning powei" dusting are dis- 

 cussed in a separate article. 



Sea soNA i . II r s tor y Recoro s . 



liecords of the emergence of 2242 spring l)]ood moths were taken 

 at Elsenburg in 1921. The earliest spring adult moths appeared 

 24th vSeptember, at the time when Kiefter and Forelle i)ears were 

 in full bloom, when the Louise Bonne pears were beginning, and 

 three days after the Duchesse trees began to blotisonr. Since the 

 weather was considerably warmer in 1921 than in 1920, iluring the 

 first two weeks of October, eggs began to hatch in the orchard the 

 second week of October, but comparatively few hatched rrntil the first 

 seven days of November, when the temiieratrrre was very high. 



]^y the 1st of No\ember, the time wherr considerable first brood 

 eggs were hatching, all pears and apple A'arieties had received at least 

 one applir-ation of arsenical spray, all pears had dropped their petals, 

 and Ohenimuri and Versveld apples were still in l)lossom, but had 

 dropped about two-thirds of their petals. It is interesting to note 

 that in 3920, the earliest spring moths begarr to emerge 8th September, 

 sixteen days earlier than in 1921, at the time Kreffer pears were in 

 full blossom just as in 1921, but many weeks earlier than the time 

 when apples dropped their petals. Even though the first spring moths 

 emerged considerably earlier in 1920 than in 1921, their eggs did not 

 begin to hatch until the end of the; first week in October, the incuba- 

 tion period being prolonged by the continued cool weather three 

 weeks before apples began to blossoiu. and as much as seven weeks 

 before the Ohenimuri and Versveld apples had dropped their petals. 

 Consequently, while in 1920, the apples which blossomed exception- 

 ally late, escaped a great majority of the first brood larvae, they 

 were exposed to most of the first brood hatching larvae in 1921. This 



