(±)‐Catechins inhibit prehaustorium formation in the parasitic weed Phelipanche ramosa and reduce tomato infestation

BACKGROUND Phelipanche ramosa L. (Pomel) is a noxious parasitic weed in field and vegetable crops in Mediterranean countries. Control of this pest is complex and far from being achieved, and new environmentally‐friendly strategies are being sought. The present study evaluates the possibility of using (±)‐catechins as a natural herbicide against broomrapes. RESULTS The results show that (±)‐catechins have no effect on GR24‐induced germination over a wide concentration range (10 −4 to 10 −10 m ), nor on radicle elongation after germination, but strongly inhibit, at 10 −4 and 10 −5 m , prehaustorium formation in response to the haustorium‐inducing factor, cis/trans ‐zeatin. Accordingly, pot experiments involving the supplies of 10 −5 m of (±)‐catechins to tomato plants infested or not with P . ramosa demonstrate that (±)‐catechins do not influence growth of non‐parasitized tomato plants and prevent heavy infestation by strongly reducing parasite attachments and inducing parasite necrosis once they are attached. CONCLUSION This study points the potential use of (±)‐catechins for parasitic weed control. It raises also the question of the mechanisms involved in the inhibition of prehaustorium formation and the necrosis of parasite attachments in response to (±)‐catechins application.