Integrated management of Imperata cylindrica (speargrass) in yam and cassava: Weed pressure in crop, crop growth and yield

The carry-over effects of different methods used to reclaim speargrass-infested lands on weed pressure, growth and yield of cassava and yam were investigated on farmers\' fields in the forest-savanna transition zone of Ghana between 2000 and 2003. The dry weight of speargrass rhizomes varied from 182 g m-2 at 5 months after planting (MAP)(17 months after treatment [MAT]) to 175 g m-2 at 12 MAP (24 MAT) on the fallow plots and plots from which speargrass was slashed before planting mucuna. No rhizomes were observed on the ploughed plots that were planted to mucuna and those that were sprayed with glyphosate or hoed before mucuna was planted at 5 MAP. The residue from mucuna suppressed speargrass for about 5 months after senescence, resulting in more vigorous and taller cassava plants and cassava root yields of 110 to 118 per cent greater for the glyphosate + mucuna plot than that for the fallow plot. Hoeing followed with mucuna had root yields of 53 to 85 per cent greater than fallow. The tuber yields of yam due to the carry-over effect of glyphosate alone resulted in 12 per cent increase in yields over fallow plots. Hoeing followed with mucuna resulted in tuber yield 50 per cent greater than that for fallow, whilst using glyphosate + mucuna recorded 112 per cent increment in tuber yields. On the ploughed plots, tuber yields of yam were 61 per cent greater than that for fallow plots when mucuna was cropped for one season and 76 per cent greater for mucuna cropped for two seasons. Growing mucuna on ploughed plots for one season was just as effective as cropping for two seasons in smothering speargrass. The results show a significant carry-over effect of an initial cultivation of the soil and mucuna and glyphosate + mucuna to control speargrass for about 5 months in a succeeding cassava and yam crop. Le transfert d'effects de différentes méthodes employées pour défricher les champs infestés de chiendent, sur la contrainte de mauvaise herbe, la croissance et le rendement de manioc et d'igname étaient enquêtés sur les champs d'agriculteurs. Les expériences étaient menées dans la zone transitionnelle de la forêt-savane du Ghana entre les années 2000 et 2003. Le poids de rhizomes secs de chiendent variaite de 182 g m-2 à 5 mois après la plantation (MAP) {17 mois après le traitement (MAT)} à 175 g m-2 à 12 MAP (24 MAT) sur les lots en jachère et les lots sur lesquels le chiendent était entaillé avant la plantation de mucuna. Il n'yavait pas de rhizomes sur les lots labourés qui étaient plantés de mucuna et ceux qui étaient pulvérisés de glyphosate ou sarclés avec la house avant que mucuna était planté à 5 MAP. Le résidu de mucuna inhibait le chiendent pour environ 5 mois après la sénescence aboutissat à des plante de manioc plus grandes et plus vigoureuses et à des rendements de racine du manioc de 110-118% plus élevés pour le lot de glyphosate + mucuna que pour le lot en jachère. Le sarclage suivi de mucuna donnait des rendements de racine de 53-85% plus élevés que la jachère. Les rendements de tubercule d'igname dû au transfert d'effet de glyphosate seule, aboutssait à 12% d'augmentation de rendements au-dessus de lots en jachère. Le sarclage suivi de mucuna donnait un rendement de tuberckule de 50% plus élevé que la jachère alors que l'utilisation de glyphosate + mucuna donnait 112% d'augmentation de rendements en tubercule. Sur les lots labourés, les rendements de tubercule d'igname étaient 61% plus élevés que ce de lots en jachère lorsque le mucuna était cultivé pour une salson et 76% plus élevés pour mucuna cultivé pour deux saisons. La culture de mucuna sur les lots laboures pour une saison était aussi efficace que la culture pour deux saisons pour couvrir le chiendent. Les résultants montrent un transfert d'effet considérable d'une culture initiale du sol et mucuna et glyphosate + mucuna pour maîtriser le chiendent pour à peu près 5 mois dans les cultures de manoic et d'igname qui ont suivi. Ghana Journal of Agricultural Science Vol. 40 (1) 2007: pp. 91-10

Storage rot of seed yam resulting from speargrass injuries

Postharvest rot due to injury is a major contributing factor to the declining quality of stored seed yams ( Dioscorea spp.). Among the several known injuries, the piercing effect of speargrass rhizomes has become a serious constraint for yam production in Ghana. The objective of this study was to assess injuries on seed yams resulting from piercing of speargrass rhizomes and their effects on postharvest rots in Ghana. Eighty farmer fields from Mem, Watro, Asanteboa and Abour in the Atebubu-Amantin Municipal in the Bono East Region of Ghana were screened for speargrass incidence and injury on harvested tubers, for laboratory analysis of pathogens in 2016 and 2017. The tubers were sorted into four categories of seed yam based on weight. Thirty seed yams each of two selected white yam cultivars (Dente and Kpamyo) with visible speargrass rhizome-pierced-tubers (VSRPT) and non-speargrass rhizome pierced healthy tubers (NSRPHT) were randomly selected and stored in a ban for weekly assessment of rot. The rotten tissues from the localised area of VPSRT were subjected to pathological investigations in the laboratory. The incidence of injury seemingly increased with increasing tuber weight. It was 0% for < 100 g samples and averagely 14% for > 1 kg samples, irrespective of cultivars and locations. Incidence of rot from NSRPHT sample was observed 5 weeks after storage (WAS) for both cultivars; and 2 WAS from the VSRPT sample and 40% higher than NSRPHT at 8 WAS. Eight and six known rot pathogens were isolated from the rotten tissues of VSRPT of Dente and Kpamyo, respectively. Injury from the piercing of speargrass rhizome significantly contributed to hastening of tuber rots; while tuber injury increased with increasing speargrass density. Appropriate management of speargrass is essential for commercial seed yam growers to reduce tuber damage which affects yam quality, storage and marketing.La pourriture post-r\ue9colte due \ue0 une d\ue9chirure est un facteur majeur contribuant \ue0 la baisse de la qualit\ue9 des ignames des semences stock\ue9es ( Dioscorea spp.). Parmi les nombreuses d\ue9chirures connues, l\u2019effet per\ue7ant des rhizomes de la gerbe d\u2019herbe est devenu une contrainte s\ue9rieuse pour la production d\u2019igname au Ghana. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer les d\ue9chirures sur les ignames de semence r\ue9sultant du per\ue7age des rhizomes de gerbe d\u2019herbe et leurs effets sur les pourritures post-r\ue9colte au Ghana. Quatre-vingts champs d\u2019agriculteurs de Mem, Watro, Asanteboa et Abour dans la municipalit\ue9 d\u2019Atebubu-Amantin dans la region de l\u2018 Est de Bono au Ghana ont \ue9t\ue9 examin\ue9s pour d\ue9terminer l\u2019incidence et les dommages de la gerbe d\u2019herbe sur les tubercules r\ue9colt\ue9s, pour une analyse en laboratoire des agents pathog\ue8nes en 2016 et 2017. Les tubercules ont \ue9t\ue9 tri\ue9s en quatre cat\ue9gories d\u2019igname de semence en fonction du poids. Trente ignames de semence de chacun des deux cultivars s\ue9lectionn\ue9s d\u2019igname blanche (Dente et Kpamyo) avec des tubercules perc\ue9s de rhizome de gerbe d\u2019herbe (VSRPT) et des tubercules sains perc\ue9s de rhizome non- gerbe d\u2019herbe (NSRPHT) ont \ue9t\ue9 s\ue9lectionn\ue9s au hasard et stock\ue9s dans une interdiction pour une \ue9valuation hebdomadaire de la pourriture . Les tissus pourris de la zone localis\ue9e de VPSRT ont \ue9t\ue9 soumis \ue0 des investigations pathologiques en laboratoire. L\u2019incidence des d\ue9chirures a apparemment augment\ue9 avec l\u2019augmentation du poids des tubercules. Il \ue9tait de 0% pour les \ue9chantillons <100 g et de 14% en moyenne pour les \ue9chantillons > 1 kg, quels que soient les cultivars et les emplacements. L\u2019incidence de pourriture de l\u2019\ue9chantillon NSRPHT a \ue9t\ue9 observ\ue9e 5 semaines apr\ue8s stockage (WAS) pour les deux cultivars; et 2 WAS de l\u2019\ue9chantillon VSRPT et 40% plus \ue9lev\ue9s que NSRPHT \ue0 8 WAS. Huit et six agents pathog\ue8nes de la pourriture connus ont \ue9t\ue9 isol\ue9s respectivement dans les tissus pourris du VSRPT de Dente et de Kpamyo. Les d\ue9chirures caus\ue9es par le per\ue7age du rhizome de gerbe d\u2019herbe ont consid\ue9rablement contribu\ue9 \ue0 acc\ue9l\ue9rer la pourriture des tubercules; tandis que les dommages aux tubercules augmentaient avec l\u2019augmentation de la densit\ue9 de la gerbe d\u2019herbe. Une gestion appropri\ue9e de la groseille verte est essentielle pour les producteurs commerciaux d\u2019ignames de semence afin de r\ue9duire les dommages aux tubercules qui affectent la qualit\ue9, le stockage et la commercialisation des ignames

Base molecular para resistência a fluazifop-p-butyl em capim-camalote (rottboellia cochinchinensis) da Costa Rica

Rottboellia cochinchinensis is an annual grass weed species known as itchgrass, or “caminadora” in America´s Spanish speaking countries, and has become a major and troublesome weed in several crops. The application of fluazifop-P-butyl at recommended rates (125 g a.i. ha-1) was observed to be failing to control itchgrass in a field in San José, Upala county, Alajuela province, Costa Rica. Plants from the putative resistant R. cochinchinensis population survived fluazifop-P-butyl when treated with 250 g a.i. ha-1 (2X label rate) at the three- to four-leaf stage under greenhouse conditions. PCR amplification and sequencing of partial carboxyl transferase domain (CT) of the acetyl-CoA carboxylase (ACCase) gene were used to determine the molecular mechanism of resistance. A single non-synonymous point mutation from TGG (susceptible plants) to TGC (putative resistant plants) that leads to a Trp-2027-Cys substitution was found. This Trp-2027-Cys mutation is known to confer resistance to all aryloxyphenoxyproprionate (APP) herbicides to which fluazifop-P-butyl belongs. To the best of our knowledge, this is the first report of fluazifop-P-butyl resistance and a mutation at position 2027 for a Costa Rican R. cochinchinensis population.Rottboellia cochinchinensis, espécie de planta daninha anual conhecida como capim-camalote, ou “caminadora”, em países de língua espanhola das Américas, tornou-se uma planta daninha significativa e problemática em diversas culturas. Observou-se que a aplicação de fluazifop-p-butyl nas doses recomendadas (125 g i.a. ha-1) não conseguiu controlar capim-camalote em uma região em San José, condado de Upala, província de Alajuela, Costa Rica. As plantas da população supostamente resistente de R. cochinchinensis sobreviveram a fluazifop-p-butyl quando tratadas com 250 g i.a. ha-1 (2X a dose do rótulo) na fase de três a quatro folhas em condições de estufa. Amplificação e sequenciamento de reação em cadeia da polimerase de domínio de transferase de ácido carboxílico parcial (TC) do gene acetil-CoA carboxilase (ACCase) foram utilizados para determinar o mecanismo molecular de resistência. Foi encontrada uma mutação de ponto não sinônimo individual de TGG (plantas suscetíveis) para TGC (plantas supostamente resistentes) que conduz a uma substituição de Trp-2027-Cys. Sabe-se que essa mutação de Trp-2027-Cys confere resistência a todos os herbicidas ariloxifenoxipropionatos (AFP) a que fluazifop-p-butyl pertence. Pelo visto, este é o primeiro relato de resistência a fluazifop-p-butyl de uma mutação na posição 2027 para uma população costarriquenha de R. cochinchinensisWest Florida Research and Education Center, University of Florida/[]//United States of AmericaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Estación Experimental Agrícola Fabio Baudrit Moreno (EEAFBM

Effect of rate and time of nitrogen fertilizer application on Striga hermonthica infestation in field-grown maize

The effects of urea and sulphate of ammonia applied at 0, 90, 120, 150 and 180 kg N ha-1 (from 1989 to 1992) and the time and rate of N application (1992) on the severity of Striga hermonthica infestation and maize yield were studied in order to compare the two sources of N fertilizer, commonly available to farmers in Ghana, in reducing S. hermonthica infestation, and to determine the rate and time of application that would minimise the deleterious effect of Striga on maize. The experiments were carried out under natural field infestations on farmers' fields (6-10 locations each year) in the Guinea Savanna zone of Ghana and replicated three times at each location on plots 5 m long and 3.6 m wide. In 1989 and 1992, higher S. hermonthica population density was recorded when urea was applied compared to sulphate of ammonia. However, there were no differences in Striga population density between the two sources of nitrogen from 1990 to 1991. Applying N at either 4 or 6 weeks after planting (WAP) maize did not affect the number of emerged Striga shoots. The rate of nitrogen applied did not influence the emergence of Striga from 1989 to 1991 as compared to 1992 when Striga population declined with increased rate of nitrogen fertilizer. Maize grain yield was unaffected by the source of nitrogen applied from 1989 to 1991. Similarly, applying N fertilizer at 4 or 6 WAP did not affect maize grain yield in 1992. However, the application of sulphate of ammonia resulted in higher maize yield compared to urea in 1992. Maize grain yield increased with increased nitrogen rate up to 90 kg ha-1 beyond which no appreciable increase was observed. A minimum of 90 kg N ha-1 is therefore required for any meaningful reduction in the deleterious effects of Striga on maize. In addition, to reduce the population of Striga in maize, it is essential to apply N fertilizers early. Ghana Jnl agric. Sci. Vol.30(2) 1997: 127-13

Storage rot of seed yam resulting from speargrass injuries

Postharvest rot due to injury is a major contributing factor to the declining quality of stored seed yams (Dioscorea spp.). Among the several known injuries, the piercing effect of speargrass rhizomes has become a serious constraint for yam production in Ghana. The objective of this study was to assess injuries on seed yams resulting from piercing of speargrass rhizomes and their effects on postharvest rots in Ghana. Eighty farmer fields from Mem, Watro, Asanteboa and Abour in the Atebubu-Amantin Municipal in the Bono East Region of Ghana were screened for speargrass incidence and injury on harvested tubers, for laboratory analysis of pathogens in 2016 and 2017. The tubers were sorted into four categories of seed yam based on weight. Thirty seed yams each of two selected white yam cultivars (Dente and Kpamyo) with visible speargrass rhizome-pierced-tubers (VSRPT) and non- speargrass rhizome pierced healthy tubers (NSRPHT) were randomly selected and stored in a ban for weekly assessment of rot. The rotten tissues from the localised area of VPSRT were subjected to pathological investigations in the laboratory. The incidence of injury seemingly increased with increasing tuber weight. It was 0% for 1 kg samples, irrespective of cultivars and locations. Incidence of rot from NSRPHT sample was observed 5 weeks after storage (WAS) for both cultivars; and 2 WAS from the VSRPT sample and 40% higher than NSRPHT at 8 WAS. Eight and six known rot pathogens were isolated from the rotten tissues of VSRPT of Dente and Kpamyo, respectively. Injury from the piercing of speargrass rhizome significantly contributed to hastening of tuber rots; while tuber injury increased with increasing speargrass density. Appropriate management of speargrass is essential for commercial seed yam growers to reduce tuber damage which affects yam quality, storage and marketing