Value of 2,4,5-TP as a pre-harvest drop spray in apples at Stanthorpe

Abstract

Trials were carried out with 2,4,5-TP as a pre-harvest drop spray on Gravenstein apples. When 2,4,5-TP was applied at a concentration of 50 p.p.m. at or shortly before the commencement of natural fruit fall, pre-harvest drop was reduced to negligible proportions (8.7 per cent. as against 25.7 per cent. in the case of ANA at the standard concentration of 10 p.p.m.). Observational data suggest that the concentration of 2,4,5-TP could be substantially reduced, if necessary, but such reduction is normally unjustified in view of the variable tree vigour in commercial orchards and other factors. The efficiency of 2,4,5-TP as a pre-harvest drop spray can be largely attributed to its long period of effectiveness (26 days as against 14 days in the case of ANA) and the consequent increased permissible latitude in timing.