The influence of fungicide choice and row width on the appearance of dithiocarbamate residues in potato

Abstract

The residues of dithiocarbamates are very often found in foodstuff monitoring programme in Slovenia. The effect of fungicide choice and time spent since the last spraying on dithicarbamate residues in potato tubers were studied in the field trials from 2003 to 2005. Four different treatments were applied in trial: exclusive and alternate spraying with fungicides on the basis of dithiocarbamates, spraying schedule without dithiocarbamates and unsprayed control. 10 plants in the field and 5 kg of tubers in storage were randomly sampled in consecutive sampling after the last spraying. The influence of row width on the dithicarbamate residue content of tubers in different depths was studied in the second experiment. Row distances of 66, 75 and 90 cm were compared using varieties Carlingford, Agria and Bright. Tuber distribution in the hill was measured using device for three-dimensional measurement of hill shape and tuber position. Tubers were sampled in two ways: in layers of 0-5 cm, 5-10 cm and deeper than 10 cm, and each tuber separately. Gas chromatography coupled with mass spectrometry was used for the analysis of dithiocarbamates. They were found only in the year 2003. The results show that the environmental conditions are the key factor for determination of dithiocarbamate residues. They have bigger influence than the amount of active substance used or other technological measures taken. Application of good farming practice enables the production of food without residues in most of the years. In certain years it is possible to find residues despite the utilization of technological recommendations and pre-harvest interval.