Browsing by Author "Torto, Saffea Joseph"

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Estimation of Cassava Crop Loss as Influenced by Grasshoppers (Zonocerus variegatus L) Infestation under Protected and Unprotected Field Conditions
(Scientific Research Publishing, 2025) Torto, Saffea Joseph
An experiment was conducted at three sites (Serabu, Gbassia and Foya) in Sierra Leone during the 2020/2021 and 2021/2022 cropping seasons to assess the cassava crop loss as influenced by grasshopper incidence and severity damage in the upland of Sierra Leone. The experiment utilized three cassava genotypes (Cocoa, SLICASS 4 and SLICASS 6) and two crop pest management practices (protected and unprotected) laid out in a Randomized Complete Block Design (RCBD) with three replications. Findings revealed significant (p < 0.05) treatment × location × year interactions for fresh storage root yield (FSRY) loss, storage root number (SRN) loss and root dry matter content (RDMC) loss. Variety cocoa had the highest percent fresh storage yield loss (20.0%), number of storage roots per plant loss (42.9%) and root dry matter content loss (17.4%), whereas SLICASS 4 had the lowest of 13.3%, 37.7% and 9.5%, respectively. These findings are useful for determination of cassava crop loss using genotypes from diverse genetic backgrounds and cultivation technologies for identification of genotypes with minimal crop loss potential, selection and production of elite cassava genotype with desired end user traits.
Farmers' perception on severity, crop loss and management practices of variegated grasshopper (Zonocerus variegatus L.) on cassava (Manihot esculenta Crantz) in Sierra Leone
(GSC Online Press, 2023-09-18) Torto, Saffea Joseph
Farmers' perception on the severity and management practices on cassava has not been fully investigated particularly across agro-ecologies in Sierra Leone. This study assessed the perception of smallholder cassava farmers on the severity of Z. variegatus L., its impacts on yield and indigenous coping management practices utilized to mitigate the infestation of grasshoppers in their cassava farms. The population of the study comprised 300 cassava farmers sampled from the north, south and eastern provinces of Sierra Leone. The study involved questionnaire research instrument administered to smallholder farmers who were farming for household consumption, those producing for sale and household consumption and those who were mainly producing for sale because their primary goal was to produce for the market. Findings revealed that farmers had perceived abilities about agro-ecological distribution of grasshoppers, making them to be familiar with cassava crop damage severity pattern and easy identification. Farmers have ability to recognize and identify adult grasshoppers, and part(s) of cassava mostly affected by grasshoppers. Cassava leaves and stems are destroyed by the pest during either preferential feeding or as a result of ‘choice, no choice feeding’. The study established that smallholder farmers have perceived abilities to identify damage symptoms, stage(s) in the life cycle of the pest that is/are more destructive leading to crop losses and utilization of best practices to mitigate grasshopper infestation on cassava that could be exploited for increased production, management and conservation of cassava genetic resources. Moreover, 52.3% of variation in extent of crop loss by grasshopper infestation is attributable to life cycle stage(s) of the grasshoppers, identification of part(s) of cassava plant mostly destroyed by grasshoppers, cassava variety preference by grasshoppers and the best practices that contribute to increased cassava productivity.
Grasshopper Incidence and Severity of Damage as Influenced by Cyanogenic Potential in Leaf Tissue of Cassava (Manihot esculenta Crantz)
(Scientific Research Publishing, 2024) Torto, Saffea Joseph
This study assessed the effect of cyanogenic potential (CNP) in leaf tissue on grasshopper incidence and severity of damage in cassava for the identiﬁcation of parents with desired complementary traits for crossing. The experiment was conducted at the Foya Wulleh, Njala experimental site in Sierra Leone during 2020 and 2021 cropping seasons in a randomized complete block design with three replications. A total of 30 genotypes comprising 26 breeding lines, two improved and two local genotypes were assessed. Results showed a signiﬁcant (p < 0.05) linear relationship between leaf CNP and grasshopper infestation (incidence and severity of damage) among cassava genotypes. Findings showed that the higher leaf CNP, the lower the grasshopper infestation in cassava genotypes. About two genotypes (Cooksoon and Cocoa) had low leaf CNP; three genotypes (TR0020, TR0037 and TR0013) CNP had moderately low leaf CNP; eight genotypes (SLICASS 6, TR0029, TR0032, TR0011, TR0012, TR0016-1/17, TR0002 and TR0010) had intermediate leaf CNP; seven (TR0009, TR0015-1/17, TR0036, TR0022-1/17, SLICASS 4, TR0007 and TR0026-1/17) had moderately high leaf CNP; eight (TR0008, TR0019-1/17, TR0006, TR0005, TR0021, TR0021-1/17, TR0022 and TR0024-1/17) had high leaf CNP; and two genotypes (TR0001 and TR0018-1/17) had very high leaf CNP. This suggests the indirect dependence of leaf cyanogenic potential on grasshopper infestation (incidence and severity of damage) in cassava that could be exploited for the genetic improvement of cassava for improved resistance to grasshopper infestation, nutrition and utilization of the crop.
Infestación de Saltamontes (Zonocerus variegatus L) y Contenido de Materia Seca en Raíces de Yuca Influenciados por la Fecha de Siembra y los Genotipos de Yuca
(Universidad Nacional Agraria La Molina, 2023-04-22) Torto, Saffea Joseph
Existe poca información sobre los efectos de las fechas de siembra y los genotipos sobre la infestación de saltamontes (Zonocerus variegatus L.) y la acumulación de materia seca en el órgano radicular de la yuca. Se realizó un experimento en el sitio experimental de la Escuela de Agricultura y Ciencias de la Alimentación, de la Universidad de Njala durante las temporadas de cultivo 2007/2008 y 2015/2016. Este estudio evaluó los efectos de la fecha de siembra y los genotipos de yuca sobre la infestación de saltamontes y la acumulación de materia seca en la raíz de la yuca. El experimento utilizó cuatro genotipos de mandioca (Cacao, SLICASS 1, SLICASS 4 y SLICASS 6) y tres fechas de siembra (junio, septiembre y diciembre) dispuestos en un diseño de bloques completos aleatorizados (RCBD) con tres repeticiones. Los resultados mostraron que la incidencia y la gravedad de los ataques de saltamontes, así como el contenido de materia seca radicular, fueron significativamente diferentes (p<0.05) entre la variedad y las fechas de plantación. Las puntuaciones de severidad del saltamontes aumentaron 3 meses después de la plantación (MAP) (1.6) a 9 MAP (2.6). Del mismo modo, la incidencia aumentó de 3 MAP (23 %) a 9 MAP (29.7 %). El porcentaje más bajo de incidencia de saltamontes se observó en junio (24.8 %), seguido de septiembre (26 %), mientras que diciembre registró el más alto (30.7 %). Se observaron tendencias similares para la puntuación de severidad en las fechas de plantación de junio (1.5), septiembre (2.2) y diciembre (2.5). El genotipo SLICASS 6 (42.21 %) tuvo el mayor contenido de materia seca radicular, seguido de SLICASS 1 (42.17 %), mientras que Cacao y SLICASS 4 tuvieron el más bajo de 41.90 %. Las parcelas protegidas registraron un mayor contenido de materia seca radicular (44 %) que las parcelas no protegidas (40.9 %). La identificación de la variedad de yuca tolerante, la protección del campo de yuca contra la infestación de saltamontes y la cosecha de yuca en diciembre podrían aprovecharse para la selección y producción de la variedad de yuca tolerante con rasgos de procesamiento deseados, tales como un alto contenido de materia seca de la raíz.
Oviposition Site Preference and Its Effects on Subsequent Development of Variegated Grasshopper (Zonocerus variegatus L.) under Laboratory Conditions
(Scientific Research Publishing, 2024) Torto, Saffea Joseph
Female grasshoppers can affect the fitness of their offspring through their selection of oviposition site. Knowledge of soil type on oviposition, and its effects on subsequent development can provide guidelines for habitat manipulations that reduce the harmful effects of these pests on farmers’ fields. The influence of soil types on the oviposition site preference of variegated grasshopper (Zonocerus variegatus L.) reared some cassava (Manihot esculenta Crantz) varieties, was investigated in a cage trial carried out at the Bio factory laboratory, School of Agriculture and Food Sciences, Njala University, Sierra Leone during 2022/2023. The treatments comprised three soil types (Sandy, Loamy and Clay), each with three replications laid out in a randomized complete block design (RCBD) in wooden cages. Data were collected on the following development parameters including, Net reproductive growth ratio (R0), Generation time (Tc), Intrinsic rate of increase (rm), Finite rate of increase (λ), Doubling time (Dt), and overall survivorship. Findings revealed that, Z. variegatus L. preferred sandy soil in which, on average, most eggs were deposited (338, 6.62 ± 4.40), followed by loamy soil, 286 (5.53 ± 3.96), and then, clayey soil, 200 (3.91 ± 3.85); though, the differences were not significant. This study established that Z. variegatus deposited more eggs in sandy soil > loamy soil > clayey soil, respectively; and subsequent survivorship of the immature unto mature adult insect, revealed a similar order. This indicates that the sandy soil is the most preferred substrate for oviposition and subsequent development into adult insects.