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Reports of damage by grasshopper Zonocerus variegatus (L.) to cassava and other crops has increased in recent years. The attack on cassava is particularly threatening to the livelihood of many poor subsistence farmers in Sierra Leone. As such, an evaluation was conducted to investigate the use of host plant resistance as an alternative method of managing grasshopper rather than the sole reliance on chemicals. The experiment was laid out in a randomized co mplete block design with three rep lications. Two b locks were used (protected and unprotected) with twenty cassava varieties (Slicass 1 05-21, VT 05-02, Slicass 2, SN 05-22, Slicass 1 05-14, Slicass 2 05-17, Slicass 5, VT 05-07, SN 05-41, Slicass 1 05-05, 97/ 3202-05-04, Slicass 4, Slicass 1 05-42, SN 05-17, Slicass 1, Local, 97/ 0057-05-04, Slicass 6, 97/0057-05-01 and Slicass 2 05-13) in each block. Pest assessments was done at 3, 6, 9 and 12 Months After Planting (MAP) which co incides with the various seasons; rain, dry and dry-rainy transition periods. Significant differences were recorded in percentage incidence and severity score with respect to cassava variety and time of observation. While seven cassava varieties (Slicass 5, VT05-02, Slicass 4, 97/0057-05-04, 97/0057-05-01, slicass 6 and Slicass 1 05-21) were found to be less susceptible to Z. variegatus (L.), four varieties (Slicass 2 05-17, Slicass1 05-41, Slicass 2 05-13 and 97/005-05-04) out yielded (in terms of tuber weight and nu mber) the released varieties during the two cropping seasons. Percent incidence and severity score was relatively high at 6MAP and 9MAP. Overall, tuber weight and number were higher in the protected plot compared to the unprotected plot during the two cropping seasons. Hence, protecting cassava field fro m grasshopper infestation may increase yield, number o f tubers and invariably the production of good quality planting material that is resistance to grasshopper attack.

Cassava Mosaic Disease (CMD) seriously affects cassava (Samura et al., 2013; Fargette et al., 1988). There is limited information on tuberous root yield loss and the profitability of growing improved and local varieties infected with the cassava mosaic virus for tuber and gari production in Sierra Leone. The objectives of the study were to determine yield loss associated with cassava mosaic disease and conduct cost benefit analysis (budgets and break-even analysis) on cassava production using two improved varieties (SLICASS 4 and 6) compared against the local susceptible variety Cocoa, for gari production and Cocoa as a poundable enterprises for the boil and eat market. Activity 1 involved the establishment of a yield loss trial using the paired plot technique. Activity 2 assessed productivity of cassava and gari production. Data collected were analysed using the analytical frame work that incorporates the concept of gross margin analysis as describe by Brown (1979). This included cost benefit analysis (CBA), the net social benefit (NSB) or the excess of total benefit over total cost represents the net present value (NPV) and The Internal Rate of Returns (IRR).The yield loss associated with the local variety Cocoa under this system was 4.27 t/ha which is equivalent to 38.92% yield loss resulting from the cassava mosaic disease infection. SLICASS 4 and SLICASS 6 recorded positive returns to production of tubers and gari. The local variety Cocoa enterprises for gari under the same condition recorded a negative returns even in the 6 year. However Cocoa for the boil and eat market had the highest profit level. The implication of this study is that breeding effort should be geared towards high yielding mosaic resistant varieties that are poundable more profitable and suits the cultural and domestic demand of the producers, processors and consumers.

The rice brown spot disease caused by Cochliobolus miyabeanus (Ito et Kurib.) Drechsl. ex Dast. = (Helminthosporium oryzae Breda da Haan) is a key disease in mangrove swamp rice ecosystem in Sierra Leone. On average, grain yield losses of 8.2-23.0% were caused by the pathogen in mangrove swamps of northwestern Sierra Leone in the 1983, 1984 and 1985 cropping seasons. Disease attack was closely linked with adverse soil conditions and favourable meteorological factors of long dew periods and moderate temperatures. However, attack by C. miyabeanus at the reproductive growth stage of rice caused the most damage because of direct effect on the grains.

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The ecological behaviour of Cochliobolus miyabeanus (Ito et Kurib.) Drechsl. ex Dast. (Bipolaris oryzae (Breda de Haan) Shoem.), causal agent of brown spot of rice (Oryza sativa L.), was investigated in a tidal mangrove swamp at Rokupr Experimental Farm, northwestern Sierra Leone. Disease increased where transplanting was delayed. This was probably due to the coincidence of flowering with favourable environmental conditions for disease development from November to February. Nitrogen fertilization at 40kg N ha -1 significantly (P = 0.05) reduced C. miyabeanus incidence in 1983, but not in 1984 and 1985 cropping seasons at the same site. Grain yields of ROK 5, a medium-duration improved rice cultivar (ca. 150 days) were significantly reduced in late-transplanted rice crops (September to November) in spite of adequate N fertilization. Mangrove mud was not an important source of C. miyabeanus propagules. Incidence of leaf scald caused by Monographella albescens (Thum) Parkinson, Sivanesan and Booth (Microdochium oryzae (Hashioka and Yokogi) Samuels and Hallet) and leaf smut caused by Entyloma oryzae Miyake were generally stimulated by N application.

Abstract:The effects of infestation by the sweet potato weevil, Cylas puncticollis Bohemen, on yield in 3 sweet potato cultivars, in relation to different mulching levels were compared. The experiment was laid out in a randomized complete split plot design at three levels. It consisted of a main plot factor, the three sweet potato cultivars (slipot 2, 3 and 4) with mulching at three levels (0, 1, 3 and 5t/ha) as sub plot. The factors were replicated thrice. The results of the studies revealed that increase in mulching level resulted in significantly decreased infestation of sweet potato weevil and higher root yield. Mulching at the rate of 5t/ha recorded the least infestation (12.13% for the year 2012; 13.32% for the year 2013) followed by 3t/ha (17.86% for the year 2012; 21.24% for the year 2013), 1t/ha (25.18% for the year 2012; 29.49% for the year 2013) whilst the unmulched plot recorded the highest (35.75% for the year 2012; 41.30% for the year 2013). Root yield was the highest with mulching at the rate of 5t/ha (6242.42Kg/ha for the year 2012; 4828.45Kg/ha for the year 2013) followed by 3t/ha (5863.64Kg/ha for the year 2012; 4883.82Kg/ha for the year 2013), 1t/ha (4580.81Kg/ha for the year 2012; 3818.18Kg/ha for the year 2013) whilst the unmulched plot recorded the highest (4202.03Kg/ha for the year 2012; 3489.89Kg/ha for the year 2013). Significant negative correlation (r = -0.91, p = 0.0001) was observed between weevil root damage and root dry matter. Only two cultivars, Slipot 3 and Slipot 4 were observed to be less susceptible to the sweetpoto weevil. Thus, using mulch cover at the rate of 3-5t/ha in a field planted with slipot 3 or slipot 4 will increase yield, while at same time reduce sweet potato weevil infestation.