Nadjia Zermane, Jürgen Kroschel, T. Souissi, M. Kharrat:
Field Survey on Orobanche Infestation of Faba Bean in Tunisia

NADJIA ZERMANE¹, JÜRGEN KROSCHEL², T. SOUISSI³, M. KHARRAT^4
1University of Kassel, Institute of Crop Science (INK), Germany
²University of Hohenheim, Institute of Plant Production and Agroecology in the Tropics and Subtropics, Germany
³Institut National d'Agronomie de Tunisie (INAT), Laboratory of Botany, Tunisia
⁴Institut National de la Recherche Agronomique de Tunisie (INRAT), Laboratory of Food Legumes, Tunisia

In Tunisia, faba bean (Vicia faba L.) is a major food legume grown for human consumption, as green pods or dry seeds, as well as for animal feed. However, the yields remain very low due to several constraints. In some areas, one of the most important constraints to faba bean production is the infestation with parasitic weeds of the genus Orobanche. To gain more information about the distribution and the impact of the parasitic weed, field surveys were carried out in April and May 2000 and 2001 in the major legume cropping areas of Tunisia mainly in the governorates of Nabeul, Béjà and Bizerte. These three governorates represent [54]% of the total faba bean growing area in Tunisia and contribute [62]% of the total production of this crop. 152 faba bean fields were investigated and the intensity of the Orobanche infestation was estimated using a scale from 0 to 6. Moreover, 90 farmers concerned by the Orobanche problem were interviewed to learn about their knowledge of the parasitic weed, their perceptions of the Orobanche problem and the control methods used.

Two Orobanche species were found infesting faba bean in the surveyed regions: O. crenata FORSK. which spreaded through the governorates of Nabeul and Bizerte and O. foetida POIRET which occurs only in the governorate of Béjà. Orobanche was present in [45]% of the surveyed faba bean fields. The infestation levels varied from low (rating scale 1 and 2, [43]% of the infested fields), to moderate or strong (rating scale 3 and 4, [29]%), to very strong (rating scale 5 and 6, [28]%). Average yield losses of faba bean due to Orobanche infestation was about [25.1]% in the three governorates. The infestation with Orobanche is considered by [70]% of the interviewed farmers as a very serious problem and [52]% of them observed an increasing infestation over time. Due to Orobanche the area allocated to faba bean is decreasing since many farmers gave up faba bean production. Thus, [84]% of the interviewed farmers in Nabeul have already abandoned faba bean production and [40]% in Bizerte intend to do it in the near future. The farmers' knowledge about the biology of the parasitic weed was very poor, [80]% of them did not know how Orobanche was reproducing and have never seen its seeds and [52]% have never seen the Orobanche underground stages. In general, no control methods are used by farmers except hand-pulling in case of low infestations. When asked about their interest to test different control methods, the majority of the farmers opted for chemicals ([100]%), trap and catch crops ([78]%) and resistant varieties, even small seeded ones ([64]%).

Keywords: Control methods, field survey, Orobanche spp., Tunisia

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Contact Address: Nadjia Zermane, University of Kassel, Institute of Crop Science (INK), Steinstraße 19, 37213 Witzenhausen, Germany, e-mail: nzermanehotmail.com