ARSENATE IN APPLES

Wanganui Chronicle, Volume LXXXII, Issue 19477, 21 December 1925, Page 11

ARSENATE IN APPLES

EXPORTERS’ PROBLEM REPLACING OF BLB. SPRAYING NELSON, Dec. 18. In reference to the cable with regard to arsenate on apples, Mr Campbell, director of the Horticulture Division, who is at present in Nelson, expressed the opinion that while the information from England must be treated seriously, the trouble (xiste.; mainly in regard to American appleSpraying apples with arsenate of lead had been the practice for the past 20 years, and for a long period before that Paris green, another arsenical spray, had been used. The cheapness of arsen ate in America no doubt led to its lavish use there, and most likely the present trouble was due to the free use of dry arsenate, quantities of which might have accumulated* round the stem. Mr Campbell said he would recommend the department’s chemists to make exhaustive tests as to the quantity of arsenate found on apples. The strength used in New Zealand was 11b of arsenate of lead to 60 gallons of water. About a third of the compound was effective arsenate, and allowing <• gallon of wash to a tree carrying, say,

! two bushels of fruit, the greatest portion would go on to the foliage, sonu lon to the trunk, and some would be | washed on to the ground. Ths estim i ated quantity of arsenate on a pound I of apples imediatcly after spraying was | certainly not more than one-tenth of a grain. This quantity was gradually reduced by rain,and wind, and by th* time the fruit was picked, graded, wrapped and packed there was practically no trace of arsenate on the apples. Growers, said Mr Campbell, must carry on spraying operations without I consideration of the development that has taken place. They should apply the spray to within a fortnight of picking. When picking the fruit should be wiped, removing any traces of the spray remaining. If this were done he did not think any complaints would be made in England about New Zealand apples, but if the crop was to escape the ravages of codlin moth ami leaf roller it, was absolutely essential to spray the fruit. No substitutes for the spray in use xvere known, am these must be depended on at present. Dr. Tillyard, of the, Cawthron Institute, remarked that the arseume which gets carried on apples is all from inter sprays, hence in any case sprays put on before .January could be continued with safety. If it were necessary to discontinue later sp ayings for codlin moth and leaf roller, this could be done at slight extra expense by using instead the method of trapping worked out by Colorado entomo’oglists. An experiment, had been carried out this season in Stevens’ orchard at Stoke, said Dr Tillyard, and the results are highly encouraging. Last week no less than 93 codlin moths were caught by fermented apple juice, and 66 of those were fertile females, full of egg*. Allowing only 200 eggs per female, over 13,000 young larvae were prevented from emerging by this catch. By using glass jars instead of wide tins much better results could be obtained, and liquid would not be spilt in high winds. Indications wore that the leaf roller was just as effectively controlled by this method as the codlin moth.

"One obvious reflection remains,’’ added the scientist. “The more we can replace sprays by biological methods of control the better it will bo for the future of tho industry.”