Determining the stripping rate of prochloraz from the fungicide dip tank in a commercial mango packhouse and the probable cause.
Swart S. H., Broekhuizen W. van, Serfontein J. J.
Author Affiliation: QMS Agri Science, PO Box 416, Letsitele 0885, South Africa.
Research Journal - South African Mango Growers' Association 24 : 78-80
Abstract : A study was conducted in South Africa to investigate the stripping rate of prochloraz from the fungicide solution used in the dip tank of a commercial mango packhouse and determine its cause. A fresh solution of 180 ml prochloraz/100 litres water was prepared on the first day. On the second day, the fungicide bath was topped up with prochloraz solution (180 g/100 litres water) to replace the volume of fungicide solution used during the packing process the previous day. On the third day, the fungicide tank was drained, cleaned and refilled with prochloraz solution at 180 ml prochloraz/100 litres water. Two one-litre samples were taken at regular intervals during the 3-day period this trial was conducted. Sampling was done immediately after fresh fungicide solution was prepared or when lost fungicide solution was replaced, before any fruit had passed through the dip tank. Thereafter, sampling was done at regular intervals while fruits were being treated. Results showed that prochloraz concentration in the fungicide solution decreased over time when fruits were treated. Concomitantly, an increase in the number of colony forming units was observed during the respective sampling periods. A strong correlation was observed between the tonnes of fruits treated and prochloraz concentration in the fungicide solution only on days 1 and 3. Prochloraz concentration did not seem to be correlated with temperature (which varied between 25.7 and 30.9°C) during the course of this trial, nor did it correlate with pH (which remained relatively steady between 7.32 and 8.04). Further investigations are needed to determine the cause of this prochloraz loss from fungicide solutions.