Mulching the soil with polyethylene sheets before sowing during the hot season, increased the soil temperatures, which resulted in the control of soil-borne pathogens and weeds. This method was tested in a field heavily infested with Egyptian broomrape (Orobanche aegyptiaca L.). Soil was irrigated and mulched for 36 days during August–September 1977, prior to sowing carrot (Daucus carota L. ‘Nantes Tip Top’) seeds. Mulching increased soil temperatures by 8 to 12 C, up to 56 C in the top 5 cm. In the non-mulched plots the carrot plants became stunted due to heavy parasitization with broomrape and they were completely destroyed by the end of the season. In contrast, broomrape and other weeds were controlled in the mulched plots and the carrot plants grew normally. This effect was less pronounced in the border rows of the mulched plots. Mulching also greatly reduced the infestation of other weeds. Egyptian broomrape was also controlled in two other field experiments with carrots and eggplants (Solanum melongena L. ‘Black oval’). As compared with fumigation, this new method of control is economical, simple, nonhazardous, and does not employ toxic materials.

The variation among and within natural populations of broomrape (Orobanche) species, a parasitic flowering plant, was determined by using random amplified polymorphic DNA (RAPD) markers. Interspecific variation was determined among five major broomrape species in Israel: O. aegyptiaca, O. mutelii, O. cernua, O. cumana and O. crenata. The pattern of interspecific variability and genetic distances observed in this study was in agreement with previous taxonomical characterization based on morphological differences among the species. Intraspecific variation was determined for O. aegyptiaca and O. crenata. Whereas 99 per cent of the amplified fragments were polymorphic among the species, only 23 per cent and 21 per cent, respectively, of the amplified fragments were polymorphic within O. aegyptiaca and O. crenata. For both species, each individual plant had a unique genotype based on a combined pattern of all the markers. No evidence was obtained for host differentiation for O. aegyptiaca and O. crenata and for regional differentiation for O. crenata.

We studied the effectiveness of glyphosate [N-(phosphono-methyl)glycine] for the control ofOrobanchespp. in the field when applied to the crop foliage prior to the emergence of the parasite. The bestOrobanchecontrol in October-sown carrots (Daucus carotaL.) parasitized byOrobanche crenataForsk. andO. aegyptiacaPers. and in December-sown broad bean (Vicia fabaL.) and peas (Pisum sativumL.) parasitized byO. crenatawas obtained by spraying twice, 2 weeks apart, in late January and in February, respectively. Carrot root yield remained unaffected by glyphosate at rates up to 200 g/ha. In heavily infested fields, carrots were irreversibly damaged by earlyOrobancheparasitism. The highest yields of pods of broad beans occurred after two or three applications of 150 g/ha glyphosate. Peas were seriously damaged by 150 g/ha. Two or three sprays of 50 g/ha glyphosate resulted in the highest green-kernel yield of pea where the soil was not heavily infested. Glyphosate effectively reducedO. cernuaLoeffl. emergence in non-irrigated tomatoes (Lycopersicum esculentumMill.), but was very phytotoxic to the crop. Glyphosate was highly effective in controllingOrobanchespp.; however, marginal selectivity may be sufficient in some crops and not in glyphosate-susceptible ones.

The variation among and within natural populations of broomrape ( Orobanche) species, a parasitic flowering plant, was determined by using random amplifie_d polymorphic D~A (RAPD) markers. Interspecific variation was determined among five maJor broomrape species in Israel: 0. aegyptiaca, 0. mute/ii, 0. cernua, 0. cumana and 0. crenata. The pattern of interspecific variability and genetic distances observed in this study was in agreement with previous taxonomical characterization based on morphological differences among the species.Intraspecific variation was determined for 0. aegyptiaca and 0. crenata. Whereas 99 per cent of the amplified fragments were polymorphic among the species, only 23 per cent and 21 per cent, respectively, of the amplified fragments were polymorphic within 0. aegyptiaca and 0. crenata. For both species, each individual plant had a unique genotype based on a combined pattern of all the markers. No evidence was obtained for host differentiation for 0. aegyptiaca and 0. crenata and for regional differentiation for 0. crenata.

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