Phelipanche aegyptiaca (Orobanchaceae) is a parasitic weed that causes severe yield losses in field crops around the world. After establishing vascular connections to the host plant roots, P. aegyptiaca becomes a major sink that draws nutrients, minerals, and water from the host, resulting in extensive crop damage. One of the most effective ways to manage P. aegyptiaca infestations is through the use of herbicides. Our main objective was to optimize the dose and application protocol of herbicides that effectively control P. aegyptiaca but do not damage the cabbage crop. The interactions between the cabbage roots and the parasite were first examined in a hydroponic system to investigate the effect of herbicides on initial parasitism stages, e.g., germination, attachment, and tubercles production. Thereafter, the efficacy of glyphosate and ethametsulfuron-methyl in controlling P. aegyptiaca was examined in five cabbage fields naturally infested with P. aegyptiaca. The herbicides glyphosate and ethametsulfuron-methyl were applied on cabbage foliage and in the soil solution, both before and after the parasite had attached to the host roots. A hormesis effect was observed when glyphosate was applied at a dose of 36 g ae ha-1 in a non-infested P. aegyptiaca field. Three sequential herbicide applications (21, 35, and 49 days after planting) effectively controlled P. aegyptiaca without damaging the cabbages at a dose of 72 g ae ha-1 for glyphosate and at all the examined doses for ethametsulfuron-methyl. Parasite control with ethametsulfuron-methyl was also effective when overhead irrigation was applied after the herbicide application.
Keywords: Phelipanche aegyptiaca; chemical control; ethametsulfuron-methyl; glyphosate.