GOLDWASSER, Y., Department of Weed Science, A.R.O, Newe Ya'ar Research Centre, P. O. Box 90000, Haifa, 31900, Israel
KLEIFELD, Y., Department of Weed Science, A.R.O, Newe Ya'ar Research Centre, P. O. Box 90000, Haifa, 31900, Israel
GOLAN, S., Department of Weed Science, A.R.O, Newe Ya'ar Research Centre, P. O. Box 90000, Haifa, 31900, Israel
BARGUTTI, A., Department of Weed Science, A.R.O, Newe Ya'ar Research Centre, P. O. Box 90000, Haifa, 31900, Israel
RUBIN, B., Department of Field Crops, Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot, 76100, Israel

The effect of metham‐sodium on Orobanche aegyptiaca Pers. was tested in the laboratory and in soil columns. The laboratory experiment was carried out on O. aegyptiaca seeds placed in Petri dishes and germinated with GR24, a synthetic strigol analogue. In soil columns, metham‐sodium was applied by application of the chemical through the irrigation water to three different soils and its dissipation determined in three soil layers by gas chromatography, by a lettuce bio‐assay to check the herbicide's phytotoxicity, and with a flax bioassay to check its effect on O. aegyptiaca. Results of the germination experiments showed an exponential decrease in O. aegyptiaca germination, parallel with the increase of metham‐sodium concentration, with an average effective concentration (EC50) of 18 mg L−1. In a soil column, methylisothiocyanate (MIT, the metham active product) rapidly disappeared from the upper soil level (0–10 cm) within 24 h. Seven days after application only traces of MIT remained in all soil layers in all soils, except for the sandy Rehovot soil that contained low concentrations in the lower soil layer (20–30 cm). Flax bioassay confirmed the chemical analysis, showing that O. aegyptiaca tubercles developed only on plants grown in the upper soil layer of all three soils. Copyright © 1995, Wiley Blackwell. All rights reserved