POTENTIAL IMPACTS OF CLIMATIC CHANGES ON INDOXACARB PERSISTENCE AND ITS PRE-HARVEST INTERVAL IN TOMATO FRUITS.

It is real and significant that climatic changes affect the pesticide behaviour, but there are no data available on their effect on the pesticide persistence and its preharvest interval (PHI). Therefore, to estimate the potential effect of climatic changes on the fate of indoxacarb in tomato fruits, the decline rate of indoxacarb residues was investigated in winter and summer seasons, for three consecutive years under field condition. Residues of indoxacarb were determined by high performance liquid chromatography with photodiode array detector (HPLCDAD). Recoveries were between 89.5-96.4% with a RSD of 8-15% in tomato at spiked levels of 0.01, 0.05 and 0.1 mg kg-1, respectively. The LOQ of this method was found to be 0.01 mg kg-1 while LOD being 0.005 mg kg-1. Indoxacarb was sprayed on tomato at recommended dosage. Samples of tomato were collected at 0, 1, 3, 5, 7, 10 and 15 days after treatment. The decline rates of indoxacarb were described using first-order kinetics. The results indicated that, the mean half-lives of indoxacarb in tomatoes and PHI changed significantly through all seasons of the trial. The least half-life time and PHI were 1.400 and 2.100 d in summer season of 2014, respectively, while the longest were 2.773 and 4.800 d in winter season of 2012, respectively. Also, a negative correlation coefficient was observed between the averages of air temperature (of days after indoxacarb spraying) in seasons of the experiment and the mean half-life times or PHis. Whereas a positive correlation coefficient was obtained between averages of relative humidities and the mean half-life times or PHis. It was concluded that both air temperature and relative humidity (as a part of climatic factors) play a great role in the interaction with indoxacarb persistence and its PHI. This work would be also helpful for the government of Egypt to establish the MRL of indoxacarb in tomato and to provide guidance on the proper and safe use of this insecticide. [ABSTRACT FROM AUTHOR]