MANAGING CYLAS SPP. WITH BOTANICALS IN SWEET POTATO CROP

Transcription

1 International Journal of Agricultural Science and Research (IJASR) ISSN Vol. 3 Issue 2, Jun 2013, TJPRC Pvt. Ltd. MANAGING CYLAS SPP. WITH BOTANICALS IN SWEET POTATO CROP APPIA-DANQUAH & K OSEI CSIR-Crops Research Institute, Kumasi, Ghana ABSTRACT Four botanicals; lemon grass (Cymbopogon citratus), neem (Azadirachta indica), garlic (Allium sativum) and chilli pepper (Capsicum fructescens) cv. Legon 18), and a synthetic pesticide, Dursban EC were evaluated for pesticidal effect on Cylas spp. The treatments were mounted on Randomized Complete Block Design (RCBD) and replicated four times. The pesticidal potential of neem was demonstrated as the combination of neem leaf amendment and neem leaf extract recorded (69, 60 and 68%) lower leaf damage than the control during the 4 th, 7 th and 10 th weeks of observation. Neem leaf soil amendment recorded the highest total number of tubers which were 24% higher than the control, while neem leaf extract recorded 11% more tubers than the control. The control recorded the highest number of holes on tubers which was three times more than the mean of all the treatments. The combination of neem leaf amendment and neem leaf extract recorded the highest yield of t/ha which was approximately 63% over the control. KEYWORDS: Allium sativum, Azadirachta indica, Capsicum fructescens, Cymbopogon citratus, Ipomoea batatas INTRODUCTION Sweet potato, Ipomoea batatas, is an important carbohydrate source in the world, particularly for Asian and African populations. It is a versatile crop; the young leaves and the shoot are sometimes eaten as greens (Zhao et al., 2005). The potential of this crop as a major raw material for industrial purposes (Kozai et al., 1996 and Woolfe, 1992) has increased its significance. In the culinary industry in Ghana, sweet potato is used in the preparation of custard, baby foods (Cerevita and Cerelac), pastries, composite flour, yoghurt and French fries. It produces more edible energy, protein and dry matter per hectare than any other crop (Ewell & Mutuvra, 1991). Also, sweet potato has early maturity period compared with yam and cassava. These attributes have placed sweet potato in the famine mitigation bracket. Sweet potato has varied pharmaceutical significance. The crop has been reported to contain pro-vitamin A or betacarotene and has the potential to reduce vitamin A deficiency (Van Jaarsveld et al., 2005). It is also used for the treatment of diabetes (Kusano et al., 2001). The consumption of sweet potato has been recommended for low blood glucose levels (Dilworth et al., 2005). In spite of the numerous benefits of the crop, its production in Ghana is at the subsistence level where farmers rarely cultivate more than one acre of land. There is however a ready local market for the crop which is an incentive for increased production. Pests infestation is a major biotic constraint to production. Nematodes for instance, represent a significant problem in sweet potato production causing reduction in yield and quality of storage roots (Ukoskit et al., 1997). Meloidogyne spp., Rotylenchulus reniformis, Pratylenchus spp. and Ditylenchus spp. are the major sweet potato pests. However, the sweet potato weevils, Cylas spp. constitute a major threat to the production of the crop (Chalfant et al., 1990; Lenne, 1991). Cylas puncticollis and C. brunneus are among the most devastating species. Losses of marketable yield as high as 60-97% has been reported (Jansson et al., 1987; Smit, 1997). Low levels of infestation can reduce root quality and marketable yield because the plants produce unpalatable terpenoids in response to weevil feeding (Uritani et al., 1975). The application of inorganic pesticides for the management of Cylas spp. though effective has been criticized on grounds of high cost of production and environmental pollution. The development of cost effective and environmentally

2 112 Appiah-Danquah& K Osei friendly management options should therefore engage the attention of researchers. The objective of this study was to evaluate some readily available botanicals for pesticidal activity against the sweet potato weevils, Cylas spp. MATERIALS AND METHODS Study Site The study was conducted at the Teaching and Research Farm of the School of Agriculture, University of Cape Coast. The trial was conducted during the major season (March-July) and repeated during the minor season (August- December, 2005). The location experiences a bimodal rainfall pattern with a mean annual rainfall of about 930 mm. Mean temperatures are relatively uniform throughout the day and ranges from 33.3ºC during the day, dropping to about 21ºC at night. Relative humidity ranges between 70-90%. The soils are the Benya series (Asamoah, 1973). Four botanicals; lemon grass (Cymbopogon citratus), neem (Azadirachta indica) leaf, garlic (Allium sativum) and chilli pepper (Capsicum fructescens) fruits cv. Legon 18), and a synthetic pesticide, Dursban EC were evaluated for pesticidal effect on Cylas spp. Two forms of lemon grass and neem leaves were used. They were either in pounded form or cold aqueous extract form. Fresh lemon grass and neem leaves were pounded in a mortar with a pistle and amended with the soil on the ridges before planting the sweet potato.the aqueous extracts of the lemon grass, neem leaves, garlic and chilli pepper were procured by blending in a Kenwood blender. Forty grams of the blended material was soaked in 1 l of distilled water for 12 h and filtered through a clean, white muslin sieve. The filtrate was collected into beakers and ten litres of the filtrate was mixed with 1 l of water and sprayed on the plants at four, seven and ten weeks after planting using a knapsack spraying machine.the ten treatments evaluated were; lemon grass applied at 500 g/ridge, aqueous extract of lemon grass at 10 l/l/ridge, neem leaf at 500 g/ridge, aqueous extract of neem leaf at 10 l/l/ridge, combination of lemon grass at 500 g and aqueous extract of lemon grass at 10 l/l/ridge, combination of neem leaf at 500 g and aqueous extract of neem leaf at 10 l/l/ridge, aqueous extract of garlic at 10 l/l/ridge, aqueous extract of pepper at 10 l/l/ridge, Dursban EC at 2 ml/l/ridge and a control. A plot measured 5 x 4 m. The treatments were mounted on a Randomized Complete Block Design (RCBD) and replicated four times. Planting Material The propagation material (vines) was obtained from Akotokyir, a nearby farming community. Apical vines of sweet potato cv. Sauti were cut into 25cm sections. Each vine cutting had 5-7 nodes. Double row planting was done on 10 m ridges at a spacing of 60 x 30 cm. The field was weeded three times before the crop was harvested. DATA COLLECTION AND ANALYSIS Parameters which were assessed in the experiment included: Mean population of Cylas spp. on sweet potato plants at 3 weekly intervals starting from the 4 th week, number of perforations on sweet potato leaves, number of total, healthy and unhealthy tubers, number of holes on sweet potato tubers at harvest and yield. Data for the two planting times was pooled and analyzed together using Genstat 8.1 statistical package (VSN International). Means were separated using Fisher s Least Significant Difference (LSD). RESULTS AND DISCUSSIONS Three treatments; neem leaf amended soil, the combination of neem leaf amended soil and neem leaf extract and lemon grass amended soil recorded the lowest mean populations. The treatments recorded (78, 69 and 65%), (80, 80.4 and 72%) and (81, 86 and 73%) significantly (P <0.05) less Cylas spp. population than the unamended control during the 4 th,

3 Managing Cylas spp. with Botanicals in Sweet Potato Crop th and 10 th weeks monitoring periods respectively (Table 1). There was no difference in population between garlic and chilli pepper extract treatments during the monitoring period. These results are in consonance with the observations of (Tandon and Siroho, 2009) and (Scott et al., 2003) who reported pesticidal properties in neem and lemon grass respectively. The pesticidal potential of neem was further demonstrated as the combination of neem leaf amendment and neem leaf extract recorded (69, 60 and 68%) significantly lower leaf damage than the control during the 4 th, 7 th and 10 th week s observations. Neem leaf and lemon grass soil amendments followed the combination of neem leaf amendment and neem leaf extract in potency recording (54, 55 and 68%) and (49, 58 and 69%) lower leaf damage than the control during the three monitoring periods respectively. Different parts of a botanical contain different active ingredients or different concentrations of the same active ingredient (Osei et al., 2010). The leaf of neem has been reported to contain Azadirachtin with antifeedant, insect repellent and insect sterilization properties (Mansha International, 2012) which prevented Cylas spp. from defoliating sweet potato. Chilli pepper and garlic were comparatively ineffective in protecting sweet potato leaves against Cylas spp. damage (Table 2). From Table 3, neem leaf soil amendment recorded the highest total number of tubers which were 24% higher than the unamended control. It also recorded relatively minimal unhealthy tubers, 69% better than the control. Neem leaf soil amendment increased the soil organic matter content which impacted positively on the total number of tubers. The nematicidal (Tariq and Siddiqui, 2005) and insecticidal (Tandon and Siroho, 2009) properties of neem might have managed nematodes, Cylas spp. and other soil arthropods that could have increased the threshold of unhealthy tubers. Chilli pepper recorded the lowest total tubers which were 35% lower than neem leaf amendment treatment but not different from the control. Chilli pepper did not have the potential to increase the number of sweet potato tubers. However, chilli pepper recorded minimal unhealthy tubers which were 52% better than the control. Cultivating sweet potato without any pest management strategy would result in low productivity and high damaged tubers. Neem leaf extract recorded significant 11% more tubers than the control. The potential of the treatment to protect sweet potato foliage from insect damage might have permitted higher photosynthetic rates which resulted in high tuber production. The unamended control recorded the highest number of holes on tubers which was three times more than the mean of all the treatments (Table 4). Neem leaf and chilli pepper extracts could not provide sufficient protection for sweet potato tubers as they recorded (63 and 69%) more holes on tubers respectively than the combination of neem leaf amendment and neem leaf extract which gave the lowest number of holes. However, lemon grass extract was as effective as the combination of neem leaf amendment and neem leaf extract. The active ingredient in lemon grass (Citral) might possess systemic properties which protected sweet potato tubers. The synthetic pesticide, Dursban EC was equally effective as it was no different from the combination of neem leaf amendment and neem leaf extract and lemon grass extract. The combination of neem leaf amendment and neem leaf extract recorded the highest yield of t/ha which was approximately 63% over the control. The treatment was however not different (P <0.05) from neem leaf amendment which yielded 60% more than the control (Table 5). Dursban EC was the next highest in yield which was not different from garlic extract. These results are comparable to the work of Atungwu et al. (2009) who reported that neem leaf powder resulted in significant reduction (192.59%) in gall formation and nematode multiplication (82.07%) and significantly high soybean grain yield of %. The performance of Dursban EC was not unexpected as synthetic pesticides have been reported to increase the yield of agricultural products ten-fold (Atungwu et al., 2009). However, environmental pollution and the disruption of the balance of nature, high cost and non-availability discount any gains synthetic pesticides may import. The search for alternative options of food production is imperative. In this study, neem was identified as the most

4 114 Appiah-Danquah& K Osei effective candidate in the production of sweet potato crop. It is also an environmentally acceptable option for pest management and food production generally. REFERENCES 1. Asamoah, G. K. (1973). Soil and proposed size of University of cape Coast. Soil Research Institute, Kwadaso, Technical Report, Ghana No Atungwu, J. J., Ademola, A. A and Aiyelaagbe, I. O. O. (2009). Evaluation of organic materials for inhibition of nematode reproduction in soybean. Afr. Crop Sci. J. 17, Chalfant, R. B., Jansson, R. K., Seal, D. R and Schalk, J. M. (1990). Ecology and management of sweet potato insects. Ann. Rev. Ento. 35, Dilworth, L. L., Omoruyi, F. O and Simon, O. R. (2005). The effect of phytic acid on the levels of blood glucose and some enzymes of carbohydrate and lipid metabolism. West Indian Med. J. 54, Ewell, P. T and Mutuvra, J. (1991). Sweet potato in the food system of eastern and southern Africa. In: Symposium on Tropical Root Crops in a Developing Economy, pp ISHS Acta Hort Jansson, R. K., Bryan, H. H & Sorensen, K. A. (1987). Within vine distribution and damage of sweet potato weevil, Cylas formicarius elegantulus on four cultivars of sweet potato in southern Florida. Florida Entomologist 70, Kozai, T., Kubota, C and Kitaya, Y. (1996). Sweet potato technology for solving the global issue on food energy, natural resources and environment in the 21 st century. Envtal. Conserv, Biotech. 34, Kussano, S., Abe, H and Tamura, H. (2001). Isolation of antidiabetic components from white-skinned sweet potato. Bioscience Biotech. Biochem. 65, Lenne, J. M. (1991). Diseases and pests of sweet potato: South East Asia, the Pacific and East Africa. Nat. Res. Inst. Bull. No. 46, pp Mansha International (2012). Neem based organic pesticides and fertilizers retrieved on 11. Osei, K., Gowen, S. R., Pembroke, B., Brandenburg, D. L and Jordan, D. L. (2010). Potential of leguminous cover crops in management of a mixed population of root-knot nematodes (Meloidogyne spp.). J. Nematol 42, Scott, I. M., Jensen, H., Scott, J. G., Isman, M. B., Arnason, J. T and Philogene, B. J. (2003). Botanical insecticides for controlling agricultural pests: piperamides and the Colorado Potato Beetle, Leptinotarsa decemlineata. Arch. Insect Biochem Physiol. 54, Smit, N. E. J. M. (1997). Integrated pest management for sweet potato in East Africa. Thesis Landbouwunieversitei Wageningen. 14. Tandon, P. and Siroho, A. (2009). Laboratory assessment of repellent properties of ethanolic extracts of four plant extracts against Raphidopalpa foveicollis. Int. J. Sustain. Crop Prodn. 4, Tariq, I. and Siddiqui, M. A. (2005). Evaluation of nematicidal properties of neem for the management of Meloidogyne incognita on tomato. Indian J. Nematol. 35,

5 Managing Cylas spp. with Botanicals in Sweet Potato Crop Ukoskit, K., Thompson, P. G., Watson, C. E and Lawrence, G. N. (1997). Identifying a randomly amplified polymorphic DNA (RAPD) marker linked to a gene or root-knot nematode resistance in sweet potato. J. Amer. Soc. Hort. Sci. 122, Uritani, I., Saito, T., Honda, H and Kim, W. K. (1975). Induction of furanoterpenoids in sweet potato roots by the larval components of the sweet potato weevil. Agric. Biol. Chem. 37, Van Jaarsveld, P., Faber, M., Tanumihardjo, S. A., Nestle, P., Lombard, C. J and Benade, A. J. (2005). Betacarotene-rich-orange-fleshed sweet potato improves the vitamin A status of primary school children assessed with the modified-relative-dose-response test. Amer. J. Clin. Nutri. 81, Woolfe, J. A. (1992). Sweet Potato: An Untapped Food Resource. Cambridge, UK. Cambridge Uni. Press, 643 pp. 20. Zhao, G., Kan, J., Li, Z and Chen, Z. (2005). Characterization and immunostimulatory activity of an (1 6 a D glucan) from the root of Ipomoea batatas. Int. Immunopharmacology 5, APPENDICES Table 1: Mean Population of Cylas spp. on Sweet Potato Plants at 3 Weeks Interval from the 4 th Week 4 th Week 7 th Week 10 th Week Lemon grass amended soil 4.00 d 6.80 cd cd Neem leaf amended soil 2.50 d 5.00 d 7.50 de Lemon grass extract spray 8.00 c bc bc Neem leaf extract spray 9.00 bc b b Lemon grass amended soil and lemon grass extract spray 4.80 d 6.00 d 7.50 de Neem leaf amended and neem leaf extract spray 3.50 d 4.80 d 5.30 d Garlic extract 9.80 bc bc b Chilli pepper extract 9.50 bc bc b Dursban EC a b bc Control ab a a Mean Lsd (5%) Table 2: Number of Perforations on Sweet Potato Leaves 4 th Week 7 th Week 10 th Week Lemon grass amendment 5.00 bc 7.00 c 9.00 c Neem leaf amendment 4.50 bc 7.80 c 9.50 c Lemon grass extract spray 9.80 a ab b Neem leaf extract spray 9.00 a ab b Lemon grass amendment and lemon grass extract spray 5.50 bc c a Neem leaf amendment and neem leaf extract spray 3.00 c 6.80 c 9.50 c Garlic extract 9.80 a bc b Chilli pepper extract 9.00 a bc b Dursban EC 7.50 ab 8.30 c 8.80 c Control 9.80 a a a Mean Lsd (5%)

6 116 Appiah-Danquah& K Osei Table 3: Mean Numbers of Total Tubers, Healthy Tubers and Unhealthy Tubers Total Healthy Unhealthy Tubers Tubers Tubers Lemon grass amendment bc abc 7.00 b Neem leaf amendment a a 5.50 b Lemon grass extract spray bc abc 5.80 b Neem leaf extract spray bc ab 7.20 b Lemon grass amendment and lemon grass extract spray b a 5.00 b Neem leaf amendment and neem leaf extract spray bc a 5.00 b Garlic extract c abc 6.50 b Chilli pepper extract cd bc 8.50 b Dursban EC bc a 3.00 b Control c c a Mean Lsd (5%) Table 4: Mean Number of Holes Caused by on Sweet Potato Tubers at Harvest Mean Tuber Damage Lemon grass amendment 3.00 c Neem leaf amendment 2.80 c Lemon grass extract spray 2.50 c Neem leaf extract spray 4.00 b Lemon grass amendment and lemon grass extract spray 2.30 c Neem leaf amendment and neem leaf extract spray 1.50 c Garlic extract 3.80 c Chilli pepper extract 4.80 b Dursban EC 2.00 c Control a Mean 4.00 Lsd (5%) 2.46 Table 5: Yield (t/ha) of Sweet Potato Mean Weight Lemon grass amendment bcd Neem leaf amendment a Lemon grass extract spray abc Neem leaf extract spray abc Lemon grass amendment and lemon grass extract spray abc Neem leaf amendment and neem leaf extract spray a Garlic extract b Chilli pepper extract cd Dursban EC b Control d Mean Lsd (5%) 3.04