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First Report of the Parasitic Plant Orobanche aegyptiaca Infecting Olive

Broomrapes (Orobanche spp.) are obligatory parasitic plants that infect the root system of vegetables and field crops worldwide resulting in severe damage. Five broomrape species are known as significant parasites of crops in Israel: O. aegyptiaca Pers., O. cernua Loefl., O. cumana Wallr., O. crenata Forssk., and O. ramose L. (1,2). Recently, O. aegyptiaca was found to parasitize roots of young olive trees (Olea europaea) in a 1-year-old plantation located in Esdraelon Valley, Israel (voucher specimens deposited in Newe-Ya'ar Weed Herbarium, Ramat Yishay, Israel). To our knowledge, this is the first time that a tree in general and olive in particular has been reported to serve as host for O. aegyptiaca. Washing the root system clearly verified connections between the parasite and olive roots. Cross sections of an attachment site confirmed the development of functional haustoria. Trees were planted in a field where tomatoes had been previously parasitized by O. aegyptiaca for several years. In April 2001, many O. aegyptiaca plants emerged under each olive tree in a total area of 0.3 ha. Additional emergence of O. aegyptiaca was observed until July 2001. The high level of Orobanche infection did not lead to visible damage in the trees. However, the mature parasite developed massive amounts of seeds, serving to increase the population of O. aegyptiaca in the field.

References: (1) D. M. Joel and H. Eizenberg. Three Orobanche species newly found on crops in Israel. Phytoparasitica 30:187, 2002. (2) C. Parker and C. R. Riches. Parasitic Weeds of the World. CAB International, Wallingford, UK, 1993.