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Weeds in human affairs in subSaharan Africa: implications for sustainable food production Full text
1991
Akobundu, I.
Sub-Saharan Africa (SSA) has the world's largest human population growth rate, some of its poorest soils, and a high incidence of crop pests. Weeds are the major pest in virtually all of the agro-ecological zones of SSA. Parasitic and perennial weeds dominate the savanna vegetation zones whereas rapidly growing annual weeds overwhelm crops in the forest vegetation zones. High weed pressure coupled with inefficient weed control practices have tied up a disproportionate percentage of SSA's economically active population in the primary task of food production and also have kept crop yields down. In the absence of organized weed research and professional training in weed science to meet the needs of the region, improved cultivars of virtually all crops fall prey to weeds, and available arable land becomes limited to that area that can be kept free of weeds. A preponderance of annual weeds in humid parts of SSA together with hard-to-kill perennial grasses and parasitic weeds in the subhumid and arid agro-ecological zones hamper crop production and frustrate farmers throughout the region. Sustainable food production in the region can be achieved by introducing improved weed management technologies and by addressing other food production constraints of the region.
Show more [+] Less [-]Efficacy and costs of handheld sprayers in the subhumid savanna for cogongrass control Full text
2005
Nielsen, O.K. | Chikoye, David | Streibig, J.C.
Cogongrass continues to be one of the most invasive weeds in the subhumid savanna. Herbicide application expenses depend on equipment costs, costs of water transport for spraying, and chemical costs. In three on-farm experiments on land heavily infested with cogongrass, the effectiveness of a knapsack sprayer (KS), a very low volume sprayer (VLV), and a rope wick (RW) applicator was tested at Ijaye, Nigeria, from 2000 to 2001. The sprayers differed in application method, price, and carrier volume required. The dose–response curves for the three applicators were identical in all parameters except at very high doses for the RW. Consequently, there were no apparent differences in glyphosate effectiveness, even when it was applied with different equipment and different carrier volumes. However, even at very high doses, the RW was not as efficient as was the KS and VLV. Actual biomass reduction of cogongrass was greater with the KS and VLV. Even though the KS and VLV generally gave better control levels than the RW, the latter is more user-friendly because it does not require protective masks, which are often unavailable in sub-Saharan Africa. In a situation with labor scarcity, weeding with the RW was cheaper than hand weeding with hoes. The VLV was more economical when used on areas larger than 10 ha than was the RW. The KS was more economical than all other methods when used on areas larger than 2 ha.
Show more [+] Less [-]Screening preemergence herbicides for weed control in cassava Full text
2020
Ekeleme, F. | Dixon, A. | Atser, G. | Hauser, S. | Chikoye, David | Olorunmaiye, P.M. | Olojede, A. | Korie, S. | Weller, S.
Screening preemergence herbicides for weed control in cassava Full text
2020
Ekeleme, F. | Dixon, A. | Atser, G. | Hauser, S. | Chikoye, David | Olorunmaiye, P.M. | Olojede, A. | Korie, S. | Weller, S.
Weed competition severely constrains cassava root yield in sub-Saharan Africa; thus, good weed control measures, including the use of herbicides, are increasingly important. Herbicide trials were conducted at five locations across eastern, western, and north-central Nigeria over two cropping seasons (2014 and 2015). Nineteen premixed PRE herbicides applied at different rates were evaluated for efficacy on weeds and selectivity on cassava. Manual hoe-weeding at 4, 8, and 12 wk after planting (WAP) and two S-metolachlor + atrazine treatments commonly used by cassava growers were included for comparison. Six of the 19 PRE herbicide treatments (indaziflam + isoxaflutole, indaziflam + metribuzin, flumioxazin + pyroxasulfone, isoxaflutole, acetochlor + atrazine + terbuthylazine, and terbuthylazine + S-metolachlor) consistently provided 80% to 98% broadleaf and grass weed control up to 8 wk after treatment. Overall, PRE herbicide treatments and cassava yield were significantly positively correlated. Herbicide treatments terbuthylazine + S-metolachlor, flumioxazin + pyroxasulfone, diflufenican + flufenacet + flurtamone (respectively, 60 + 60 + 60, 120 + 120 + 120, 90 + 360 + 120, and 135 + 360 + 180 g ha−1), acetochlor + atrazine + terbuthylazine (875 + 875 + 875 g ha−1), S-metolachlor + atrazine (870 + 1,110 g ha−1), oxyfluorfen (240 g ha−1), indaziflam + isoxaflutole (75 + 225 g ha−1), indaziflam + metribuzin (75 + 960 g ha−1), and aclonifen + isoxaflutole (500 + 75 g ha−1) contributed to yields exceeding twice the Nigerian national average of 8.76 tonnes ha−1. These treatments had root yields of 1.4 to 2 times higher than plots that had been hoe-weeded three times. There were some adverse herbicide treatment effects such as delayed cassava sprouting and temporary leaf bleaching observed in indaziflam and diflufenican + flufenacet + flurtamone treatments, whereas sulfentrazone caused prolonged leaf crinkling. The PRE applications alone at rates safe for cassava did not provide adequate season-long weed control; supplemental POST weed control is needed about 10 WAP for satisfactory season-long control.
Show more [+] Less [-]Screening preemergence herbicides for weed control in cassava Full text
2020
Ekeleme, Friday | Dixon, Alfred | Atser, Godwin | Hauser, Stefan | Chikoye, David | Olorunmaiye, Patience M. | Olojede, Adeyemi | Korie, Sam | Weller, Stephen
Weed competition severely constrains cassava root yield in sub-Saharan Africa; thus, good weed control measures, including the use of herbicides, are increasingly important. Herbicide trials were conducted at five locations across eastern, western, and north-central Nigeria over two cropping seasons (2014 and 2015). Nineteen premixed PRE herbicides applied at different rates were evaluated for efficacy on weeds and selectivity on cassava. Manual hoe-weeding at 4, 8, and 12 wk after planting (WAP) and two S-metolachlor + atrazine treatments commonly used by cassava growers were included for comparison. Six of the 19 PRE herbicide treatments (indaziflam + isoxaflutole, indaziflam + metribuzin, flumioxazin + pyroxasulfone, isoxaflutole, acetochlor + atrazine + terbuthylazine, and terbuthylazine + S-metolachlor) consistently provided 80% to 98% broadleaf and grass weed control up to 8 wk after treatment. Overall, PRE herbicide treatments and cassava yield were significantly positively correlated. Herbicide treatments terbuthylazine + S-metolachlor, flumioxazin + pyroxasulfone, diflufenican + flufenacet + flurtamone (respectively, 60 + 60 + 60, 120 + 120 + 120, 90 + 360 + 120, and 135 + 360 + 180 g ha–¹), acetochlor + atrazine + terbuthylazine (875 + 875 + 875 g ha–¹), S-metolachlor + atrazine (870 + 1,110 g ha–¹), oxyfluorfen (240 g ha–¹), indaziflam + isoxaflutole (75 + 225 g ha–¹), indaziflam + metribuzin (75 + 960 g ha–¹), and aclonifen + isoxaflutole (500 + 75 g ha–¹) contributed to yields exceeding twice the Nigerian national average of 8.76 tonnes ha–¹. These treatments had root yields of 1.4 to 2 times higher than plots that had been hoe-weeded three times. There were some adverse herbicide treatment effects such as delayed cassava sprouting and temporary leaf bleaching observed in indaziflam and diflufenican + flufenacet + flurtamone treatments, whereas sulfentrazone caused prolonged leaf crinkling. The PRE applications alone at rates safe for cassava did not provide adequate season-long weed control; supplemental POST weed control is needed about 10 WAP for satisfactory season-long control.
Show more [+] Less [-]Rimsulfuron for postemergence weed control in corn in humid tropical environments of Nigeria Full text
2007
Chikoye, David | Udensi, U.E. | Lum, A.F. | Ekeleme, F.
Cogongrass and guineagrass are serious perennial weeds in small-scale farms in lowland subhumid zones of West Africa. Field studies were conducted in 2002 and 2003 at two sites in Ibadan, Nigeria [Ijaye and the International Institute of Tropical Agriculture (IITA)], to evaluate the effect of rimsulfuron on weed communities dominated by cogongrass and guineagrass in corn. At both sites, treatments were rimsulfuron dosages of 0 (nontreated control), 10, 20, 30, 40, 50, 60, 70, and 80 g ai/ha. Rimsulfuron did not cause any visible phytotoxicity on the corn at any dosage at either site. There was a rapid increase in weed control as the dosage of rimsulfuron increased from 0 to 20 g/ha. Weed control was not improved at rates higher than 20 g/ha. Rimsulfuron was very effective against sedges, Ipomoea involucrata, Bengal dayflower, gulf leafflower, old-world diamond-flower, and wild jute providing more than 80% control at dosages between 10 and 20 g/ha at Ijaye. Rimsulfuron was less effective for cogongrass, with a maximum of only 38% control observed. At IITA, the herbicide was very effective against guineagrass, Bengal dayflower, nodeweed, coat buttons, redfruit passionflower, and waterleaf; all of which were controlled more than 70% with any rate of rimsulfuron. Regression analysis showed that the dosage of rimsulfuron required to reduce shoot dry biomass by 70% was 5 g/ha for guineagrass and 35 g/ha for cogongrass at 3 wk after treatment (WAT). At crop maturity, the dosage of rimsulfuron required to reduce shoot dry biomass by 70% was 43 g/ha for guineagrass and 200 g/ha for cogongrass. The dry biomass of cogongrass and guineagrass was higher at crop harvest than at 2 WAT regardless of herbicide dosage. Corn grain yield was 1.8 times higher at IITA than at Ijaye. At both sites, corn grain yield increased with increased herbicide dosage. Maximum corn grain yields were obtained at a rimsulfuron dosage of 20 g/ha. Nomenclature: Rimsulfuron; coat buttons, Tridax procumbens L. TRQPR; cogongrass, Imperata cylindrica (L.) Beauv. IMPCY; old-world diamond-flower, Oldenlandia corymbosa L. OLDCO; guineagrass, Panicum maximum Jacq. PANMA; gulf leafflower, Phyllanthus amarus Schum. & Thonn. PYLAM; nodeweed, Synedrella nodiflora (L.) Gaertn SYDNO; redfruit passionflower, Passiflora foetida L. PAQFO; sedges, Cyperus, Mariscus, and Kyllinga spp; Bengal dayflower, Commelina benghalensis L. COMBE; waterleaf, Talinum triangulare (Jacq.) Willd TALTR; wild jute, Corchorus tridens L. CRGTR; corn, Zea mays L. ‘TZL Comp 4W’.
Show more [+] Less [-]Effect of nicosulfuron dosages and timing on the post emergence control of cogongrass (Imperata cylindrica) in corn (Zea mays) Full text
2005
Fontem Lum, A. | Chikoye, David | Adesiyan, S.
Cogongrass is an aggressive perennial weed, which causes severe yield losses in major crops of the moist savanna of West Africa. Field studies were conducted from 2000 to 2002 at Alabata and Ilorin, Nigeria, to evaluate the influence of dosage and time of nicosulfuron application on the control of cogongrass and corn grain yield. Nicosulfuron dosages were 50, 100, 150, and 200 g ai/ha applied 1, 2, 3, or 4 wk after planting (WAP) corn. Hand-weeded and nonweeded treatments were the controls. Three to 4 wk after treatment and at final harvest, all plots that received nicosulfuron had significantly lower cogongrass shoot dry matter (DM) than the nonweeded control across locations in all years (P ≤ 0.01). Nicosulfuron increased corn grain yield at Alabata by 96% in 2000, 100% in 2001, and 34 to 54% in 2002, and at Ilorin by 79 to 83% in 2001 and 60 to 69% in 2002 when compared with the nonweeded control. The weeded control had corn grain yield similar to plots that received nicosulfuron at 200 g/ha at Alabata in 2001, 150 g/ha at Ilorin in 2001, 50 to 200 g/ha at Alabata in 2002, and 150 and 200 g/ha at Ilorin in 2002. There were negative linear relationships between corn DM, grain yield, and cogongrass shoot DM. Application of nicosulfuron at 1 or 2 WAP, when cogongrass was 22 to 27 cm tall, gave better grain yield and lower cogongrass shoot DM than at 3 or 4 WAP, when cogongrass was 36 to 45 cm tall. The study concludes that 150 to 200 g/ha of nicosulfuron applied at 1 or 2 WAP is effective for cogongrass control without adverse effect on corn grain yield.
Show more [+] Less [-]Options for cogongrass ((Imperata cylindrica) control in white guinea yam (Dioscorea rotundata) and cassava (Manihot esculenta)1 Full text
2006
Chikoye, David | Ellis-Jones, J. | Kormawa, P.M. | Udensi, U.E. | Ibana, S. | Avav, T.
Cogongrass is a serious weed in small-scale farms in the lowland humid zone of West Africa. This study evaluated the response of cogongrass to herbicides and the legume cover crop velvetbean in cassava and white Guinea yam. In 2001/2002, cassava tuber yields and gross returns in treatments that received glyphosate alone were higher than in plots that received fluazifop-P-butyl once. In 2002/2003, treatments that received fluazifop-P-butyl once, glyphosate alone, glyphosate integrated with sowing velvetbean, or hoeing only, had higher cassava tuber yields than other treatments. Gross returns were higher in treatments that received glyphosate followed by sowing velvetbean or those hoed only than in other treatments. Fluazifop-P-butyl applied twice, glyphosate alone, or glyphosate followed by sowing velvetbean reduced cogongrass shoot biomass more than other treatments. Rhizome biomass was lower in plots that received glyphosate alone than in all fluazifop-P-butyl treatments. In 2002, white Guinea yam tuber yields were highest in plots that received glyphosate alone and lowest in plots where fluazifop-P-butyl was applied alone or followed by sowing velvetbean. The highest gross return was obtained in plots that received glyphosate alone while the lowest was obtained in plots that received fluazifop-P-butyl once followed by sowing velvetbean. In 2003, the highest tuber yields and gross returns were from plots that received glyphosate alone, fluazifop-P-butyl alone, or those hoed only. The hoed-only plots had 14 times higher cogongrass shoot biomass and 7 times higher rhizome biomass than other treatments. In both crops, hoeing alone or followed by sowing velvetbean was more costly than chemical control. The highest margin over hoeing was obtained from plots that received glyphosate alone. Sensitivity analysis showed that using glyphosate was more cost effective than fluazifop-P-butyl, even if the cost of the herbicide increased by 100% or the cost of labor decreased by 30%.
Show more [+] Less [-]Cultivar and Weeding Effects on Weeds and Rice Yields in a Degraded Upland Environment of the Coastal Savanna Full text
2011
Touré, A. | Rodenburg, J. | Saito, Kazuki | Oikeh, S. | Futakuchi, K. | Gumedzoe, D. | Huat, J.
Cultivar and Weeding Effects on Weeds and Rice Yields in a Degraded Upland Environment of the Coastal Savanna Full text
2011
Touré, A. | Rodenburg, J. | Saito, Kazuki | Oikeh, S. | Futakuchi, K. | Gumedzoe, D. | Huat, J.
Weeds are a major constraint to rice production in labor-limited, upland rice-based systems in West Africa. The effects of weeding regimes and rice cultivars on weed growth and rice yield were investigated at two upland locations (Abomey-Calavi and Niaouli) in the degraded coastal savanna zone of Benin in 2005 and 2006 with below-average rainfall. Four weeding regimes (hoe weeding at 21 d after sowing [DAS], delayed hoe weeding at 31 DAS, hoe weeding at 21 and 42 DAS, and a no weeding control) were the main plot treatments. Cultivars comprising three interspecific upland rice cultivars (NERICA 1, NERICA 2, and NERICA 7) and the parents (Oryza sativa WAB56-104 and O. glaberrima CG14) were tested in subplots. The most dominant weed species identified were Jamaican crabgrass, Mariscus, and silver spinach. Rice yield was generally low because of drought stress; none of the experiments had a higher mean yield than 1,400 kg ha−1 across cultivars. Across cultivars, the best weeding regimes in terms of weed control and rice yields were single weeding at 31 DAS (W31) and double weeding at 21 and 42 DAS (W21+42). Under these weeding regimes, WAB56-104 out-yielded the three NERICA cultivars. CG14 showed the strongest weed suppressive ability (WSA) in Abomey-Calavi but did not have strong WSA in Niaouli because of lower biomass accumulation. WSA of WAB56-104 was similar to that of the three NERICA cultivars. Single weeding at 31 DAS, together with the use of cultivars with good adaptation to unfavorable rice growing conditions, would increase land and labor productivity of upland rice-based systems in West Africa.
Show more [+] Less [-]Cultivar and weeding effects on weeds and rice yields in a degraded upland environment of the coastal savanna Full text
2011
Touré A. | Rodenburg J. | Saito K. | Oikeh S. | Futakuchi K. | Gumedzoe D. | Huat J.
Weeds are a major constraint to rice production in labor-limited, upland rice-based systems in West Africa. The effects of weeding regimes and rice cultivars on weed growth and rice yield were investigated at two upland locations (Abomey-Calavi and Niaouli) in the degraded coastal savanna zone of Benin in 2005 and 2006 with below-average rainfall. Four weeding regimes (hoe weeding at 21 d after sowing [DAS], delayed hoe weeding at 31 DAS, hoe weeding at 21 and 42 DAS, and a no weeding control) were the main plot treatments. Cultivars comprising three interspecific upland rice cultivars (NERICA 1, NERICA 2, and NERICA 7) and the parents (Oryza sativa WAB56-104 and O. glaberrima CG14) were tested in subplots. The most dominant weed species identified were Jamaican crabgrass, Mariscus, and silver spinach. Rice yield was generally low because of drought stress; none of the experiments had a higher mean yield than 1,400 kg ha-1 across cultivars. Across cultivars, the best weeding regimes in terms of weed control and rice yields were single weeding at 31 DAS (W31) and double weeding at 21 and 42 DAS (W21+42). Under these weeding regimes, WAB56-104 out-yielded the three NERICA cultivars. CG14 showed the strongest weed suppressive ability (WSA) in Abomey-Calavi but did not have strong WSA in Niaouli because of lower biomass accumulation. WSA of WAB56-104 was similar to that of the three NERICA cultivars. Single weeding at 31 DAS, together with the use of cultivars with good adaptation to unfavorable rice growing conditions, would increase land and labor productivity of upland rice-based systems in West Africa. (Résumé d'auteur)
Show more [+] Less [-]Site-specific treatment of late-season weed escapes in rice utilizing a remotely piloted aerial application system Full text
2025
Gurjar, Bholuram | Sapkota, Bishwa | Torres, Ubaldo | Ceperkovic, Isidor | Kutugata, Matthew | Kumar, Virender | Zhou, Xin-Gen | Martin, Daniel | Bagavathiannan, Muthukumar
Site-specific treatment of late-season weed escapes in rice utilizing a remotely piloted aerial application system Full text
2025
Gurjar, Bholuram | Sapkota, Bishwa | Torres, Ubaldo | Ceperkovic, Isidor | Kutugata, Matthew | Kumar, Virender | Zhou, Xin-Gen | Martin, Daniel | Bagavathiannan, Muthukumar
Drone technology and digital image analysis have enabled significant advances in precision agriculture, especially in site-specific treatment of weed escapes in crop fields. This study evaluated a pipeline for weed detection in multispectral drone imagery, along with site-specific herbicide application, using a remotely piloted aerial application system (RPAAS) targeting late-season weed escapes in rice with a selective postemergence rice herbicide, florpyrauxifen-benzyl. The efficacy of the RPAAS-based herbicide application with geocoordinates of weed escapes obtained manually or based on image analysis was compared with conventional backpack broadcast spray. The weed species targeted were barnyardgrass, Amazon sprangletop, yellow nutsedge, and hemp sesbania. A Python-based rice–weed detection model was developed using the canopy height model and spectral reflectance of weeds and rice plants. Results indicate that the accuracy of image-based detection for late-season weed escapes in rice was highest for hemp sesbania (95%), followed by Amazon sprangletop (87%) and yellow nutsedge (74%), with barnyardgrass showing the lowest accuracy at 62%. The study found that the backpack broadcast method had the highest efficacy in weed control, followed by the RPAAS method using manually obtained geocoordinates and those based on image analysis. Site-specific herbicide application using RPAAS resulted in a 45% reduction in herbicide compared to the broadcast backpack application. Moreover, the RPAAS site-specific application method for late-season treatment minimized the field area affected by herbicide injury and protected rice grain yields compared to the broadcast method. Overall, the utility of unmanned aerial sprayer–based detection and site-specific treatment of late-season weed escapes in rice has been demonstrated in this research, but further improvements in weed detection efficacy and the accuracy of targeting plants with RPAAS are necessary.
Show more [+] Less [-]Site-Specific Treatment of Late-Season Weed Escapes in Rice Utilizing a Remotely Piloted Aerial Application System Full text
2025
Bholuram Gurjar | Bishwa Sapkota | Ubaldo Torres | Isidor Ceperkovic | Matthew Kutugata | Virender Kumar | Xin-Gen Zhou | Daniel Martin | Muthukumar Bagavathiannan
Drone technology and digital image analysis have enabled significant advances in precision agriculture, especially in site-specific treatment of weed escapes in crop fields. This study evaluated a pipeline for weed detection in multispectral drone imagery, along with site-specific herbicide application, using a remotely piloted aerial application system (RPAAS) targeting late-season weed escapes in rice with a selective postemergence rice herbicide, florpyrauxifen-benzyl. The efficacy of the RPAAS-based herbicide application with geocoordinates of weed escapes obtained manually or based on image analysis was compared with conventional backpack broadcast spray. The weed species targeted were barnyardgrass, Amazon sprangletop, yellow nutsedge, and hemp sesbania. A Python-based rice–weed detection model was developed using the canopy height model and spectral reflectance of weeds and rice plants. Results indicate that the accuracy of image-based detection for late-season weed escapes in rice was highest for hemp sesbania (95%), followed by Amazon sprangletop (87%) and yellow nutsedge (74%), with barnyardgrass showing the lowest accuracy at 62%. The study found that the backpack broadcast method had the highest efficacy in weed control, followed by the RPAAS method using manually obtained geocoordinates and those based on image analysis. Site-specific herbicide application using RPAAS resulted in a 45% reduction in herbicide compared to the broadcast backpack application. Moreover, the RPAAS site-specific application method for late-season treatment minimized the field area affected by herbicide injury and protected rice grain yields compared to the broadcast method. Overall, the utility of unmanned aerial sprayer–based detection and site-specific treatment of late-season weed escapes in rice has been demonstrated in this research, but further improvements in weed detection efficacy and the accuracy of targeting plants with RPAAS are necessary.
Show more [+] Less [-]Economic control of weeds in wheat, Triticum aestivum.
1988
Gillespie G.R. | Nalewaja J.D.