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Spatial distribution and density of Striga hermonthica (Del.) benth infestation associated with cereal production in southern guinea savanna farming systems

Abstract This study describes the distribution patterns of S. hermonthica infestation present in 117 farmers’ fields located in 61 villages in the three major cereal growing areas of Benue and Nasarawa states. A total of 1098 respondents were randomly selected proportionate to the number of households in all the zones. Striga count was taken using a quadrat and farmers’ fields were visually assessed using a five-category ranking (very high density,high density, medium, low, very low density) and recording the geo referenced data. On average, 67.3 and 3.2% of the surveyed area were infested with high and low density of Striga, respectively. The mean number of Striga plants per m2 was greater at Nassarawa State (one to eighteen plants m-2) than Benue State (one to twelve plants m -2). In Benue, the largest percentage of Striga infestation was recorded in Buruku (49.7%) and the lowest was obtained in Guma (38.3%). In Nassarawa, under sorghum cultivation, higher Strigadensties were recorded in Karu and Awe LGA; while Doma, Keana and Obi LGA recorded moderate Striga infestation. In both locations, Striga infestation was highest in sorghum fields; while millet fields recorded the least. About 40% and 35.4% of the farmers reported that new modern farming methods and Striga control copping strategies, respectively are received from Extension agents , during Monthly Technology Review Meeting (MTRM). The study has provided baseline information on the spread of S. hermonthica in the Southern Guinea Savanna of Nigeria and therefore, copping strategies for its control should be intensified.

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9°0'0"N 8°0'0"N 7°0'0"N 9°0'0"N 8°0'0"N 7°0'0"N 0 5 10 20 Miles 9°0'0"N 8°0'0"N 7°0'0"N 9°0'0"N 8°0'0"N 7°0'0"N J. Bio. & Env. Sci. 2014 7°0'0"E 8°0'0"E 9°0'0"E 10°0'0"E Toto Karu Akwanga Wamba KeffiKokona Nassarawa Egon Lafia NASSARAWA Nassarawa Obi Doma Keana Awe . Agatu Guma Density of Striga Markurdi Apa Gwer West Tarka Logo Ukum 0.000000 (No Data) 0.000001 - 1.730000 (Very Low) BENUEBukuru 1.730001 - 2.020000 (Low) Gwer East Gboko Katsina- Ala 2.020001 - 2.260000 (Medium) Oturkpo 2.260001 - 2.780000 (High) Ohimini 2.780001 - 3.540000 (Very High) States Ogbadigbo Okpokwu Obi KonshishaUshongo Ado Oju Vandeikya Kwande Fig. 1. Spatio-satellite map of Benue state showing the surveyed locations. 7°0'0"E 0 15 30 60 Kilometers 8°0'0"E 9°0'0"E 10°0'0"E Fig. 3. Map of Benue North and Nasarawa State showing the density of S. hermonthica in the sampled area under maize cultivation. 7°0'0"E 8°0'0"E 9°0'0"E 10°0'0"E Toto Karu Akwanga Wamba KeffiKokona Nassarawa Egon Lafia NASSARAWA Nassarawa Obi Doma Keana Awe . Fig. 2. Spatio-satellite map of Nasarawa state showing the surveyed locations. The average percentage of Striga infested area in Benue state (one to twelve plants m -2 ) was 36.1% and was fairly greater than the 34.4% area of Nasarawa state (one to eighteen plants m -2 ). Important differences were observed among fields. Differences were found in the percentage of infestation of Striga within the ‘zone B’ study area of Benue state. The largest percentage of field area infested by Striga was observed in Buruku (49.7%), followed by Guma (45.4%) and Gwer (38.3%) (Table 3). In Buruku, an average Striga density of 12 plant m -2 was recorded, whereas in Guma and Gwer – west, this density was observed at 3 plant m -2 . In contrast, on average only 0 – 2 plant m -2 of the Striga density was slightly infested in Gboko, Gwer, Makurdi and Tarka under maize (fig. 3). Density of Striga 0.000000 (No Data) 0.000001 - 2.100000 (Very Low) 2.100001 - 3.180000 (Low) 3.180001 - 4.110000 (Medium) 4.110001 - 4.520000 (High) 4.520001 - 5.250000 (Very High) States 7°0'0"E Agatu Apa Ogbadigbo Okpokwu Gwer East Oturkpo Ohimini Ado Oju 0 30 60 15 Kilometers 8°0'0"E Guma Markurdi Gwer West Obi Tarka BENUE Gboko KonshishaUshongo Logo Vandeikya 9°0'0"E Bukuru Ukum Katsina- Ala Kwande 10°0'0"E Fig. 4. Map of Benue North and Nasarawa State showing the density of S. hermonthica in the sampled area under sorghum cultivation. The level of infestation in Nasarawa state ranged from 0.0 to 67.3% of the area irrespective of the host crops grown (Table 4). Under sorghum cultivation, the density of Striga was higher in Karu and Awe. Nassarawa and Toto LGA recorded a slightly high density, but moderate infestation was observed at the southern zone of Doma, Lafia, Keana and Obi LGA (Fig. 4). This result confirms the prevalence of Striga in the two states. Similar incidence was reported in Benue state (Suleet al., 2008; Lagokeet al., 1997). In respect to millet, a very few number of Striga were recorded in the field in relation to area of infestation and density of Striga (Fig. 5). This may presumed 424 | Ibrahim et al.

7°0'0"N 7°0'0"N 8°0'0"N 8°0'0"N 9°0'0"N 9°0'0"N J. Bio. & Env. Sci. 2014 that most of the millet cultivars that are grown in the area are tolerant variety that can withstand the effects of Striga parasitism. 7°0'0"E Density of Striga Toto 0.000000 (No Data) 0.000001 - 0.190000 (Very Low) Karu Akwanga Wamba KeffiKokona Nassarawa Egon Lafia NASSARAWA Nassarawa Agatu Apa 8°0'0"E Doma . 0.190001 - 0.260000 (Low) Bukuru 0.260001 - 0.420000 (Medium) Gwer East Gboko Katsina- Ala Oturkpo 0.420001 - 0.590000 (High) Ohimini 0.590001 - 1.080000 (Very High) Okpokwu Obi KonshishaUshongo States Ogbadigbo 7°0'0"E Ado Oju 0 30 60 15 Kilometers 8°0'0"E Obi Keana Guma Markurdi Gwer West Tarka 9°0'0"E Awe BENUE Logo Vandeikya 9°0'0"E Ukum Kwande 10°0'0"E 10°0'0"E Fig. 5. Map of Benue North and Nasarawa State showing the density of S. hermonthica in the sampled area under millet cultivation. All the fields surveyed were considered by their farmers as Striga infested, and most of them had been treated with several control strategies to contain the menace due to Striga. The differences in the agricultural farming practices and awareness of the new farming technologies among farmers could explain the observed differences. It is widely recognized that the most likely method to control Striga is the development of an integrated strategy that combines a range of technologies (Berneret al., 1996; Emechebeet al., 2004). In this study, the farmers ranked crops in their order of economic importance as a source of food. In ‘zone B’, the five most important crops were maize, rice, sorghum, yam and cassava, while in Northern zone of Nasarawa state, maize, sorgbhum, egusi-melon, rice and sesame surpassed the list (Table 5). The southern and central zones have maize and rice as the major crops. Sorghum was considered as the third-most important crop in the central zone, whereas yam was rated as the third crop in descending order of importance in the southern zone. Table 5. Farmers’ ranking of crop priority in BNARDA zone B of Benue and NADP agricultural zones of Nasarawa states, 2010. Crop Scientific name Benue Nasarawa state(NADP) Zone B Northern Central Southern Bambara nut Voandzeiasubterrarea L. 11 - 22 19 Banana Musa sapientum L 15 16 10 12 Benniseed Sesamumindicum L. 6 5 7 4 Cassava MannihotesculentaGrantg 5 6 5 9 Cashew Anacardiumoccidentale L. 16 17 9 17 Cocoyam Colocasiaesculenta Scott 20 - - - Cowpea Vignaunguiculata (L) Walp 10 8 12 6 Egusi melon Colocynthiscitruthus (L) Ktze 19 3 8 7 Ground nut Arachis hypogea L. 18 9 11 14 Guinea corn Sorghum bicolor (L) Moench 3 2 3 5 Maize Zea mays L. 1 1 1 1 Mango Mangiferaindica L. - 18 13 - Millet Pennisetumtyphoides (Burm) 17 15 14 8 Okra Abelmosochusesculentus (L) Moench 12 13 16 15 Oil palm ElaiesisguineensisJacq. - - 18 - Plantain Musa paradisiaca L. - - 19 - Pepper Capsicum annum L. 9 14 23 16 Rice Oryza sativa L. 2 4 2 2 Soyabean Glycine max (L) Merr. 8 11 15 18 Sugarcane Saccharumofficinarum L. 22 10 17 13 Sweet orange Citrus siwensis (L) Osbeck 13 19 21 10 Sweet potato Ipomeabatatas (L) Lam 14 12 6 14 Tobacco Nicotianatabacum L. 21 - - - Tomato Lycopersiconesculentum L. 7 8 19 11 Water yam DiscorearotundataPior - - 20 20 Yam D. alata L. 4 7 4 3 425 | Ibrahim et al.

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