AGRICULTURE AND BIOLOGY JOURNAL OF NORTH AMERICA ISSN Print: 2151-7517, ISSN Online: 2151-7525, doi:10.5251/abjna.2011.2.1.1.5 2011, ScienceHuβ, http://www.scihub.org/abjna Comparative efficacy of oil palm inflorescence ash, orange peels ash and benlate in preservation of cassava tubers (Manihot esculenta Crantz) *Ayodele 1, S. M., and Iwhiwhu 2, O. C. 1 Department of Biological Sciences, Kogi State University, P. M. B. 1008, Anyigba, Kogi State Nigeria. Email: ayodelemichaeln2007@yahoo.com 2 Department of Botany, Delta State University, Abraka, Delta State, Nigeria. ABSRACT The relative efficacy of oil palm inflorescence and orange peels ash pastes and Benlate fungicides were assessed for preservation of cassava tubers (Manihot esculenta Crantz) for 8 weeks. The ashes were applied as pastes on the tuber surface. Benlate was applied at a concentration of 1,000ppm (active ingredient). There was a variation in fresh weight loss which was influenced by the various treatments. Loss in fresh weight was least in tubers treated with oil palm inflorescence ash paste followed by orange peels ash paste. The same trend was also observed in rot development and severity. The two ash pastes proved better than Benlate fungicide in controlling fresh weight loss, rot development and rot severity. The results indicate that ash pastes from oil palm inflorescence and orange peels could be used in practical control of storage rot of cassava tubers and other tuber crops. Keywords:-Comparative, efficacy, oil palm inflorescence, orange peels, ash, Benlate, fresh weight loss, cassava tubers. INTRODUCTION Efforts made by man to cultivate crops in abundance, especially in developing countries have been frustrated by lack of storage facilities and preservation methods. As a result of these, some crops become surplus at certain period of the year and become scarce and expensive at other period. Cassava (Manihot esculenta Crantz) is one of the most popular root tubers in many African countries. It is grown exclusively as food in 31 African countries (Hahn and Keyser, 1985). It has become a staple food providing about 50% of the energy requirements for millions of people in the African continent (IITA, 1985). Cassava tubers are used for various purposes ranging from Garri to Apu, Tapioca and even bread in Nigeria. Cassava tubers are usually consumed or processed almost immediately they are harvested. This is due to lack of preservation methods for the crop. Most of the preservation methods of the crop are by leaving the crops on the farm unharvested until when needed or the tubers are harvested, sliced and sun dried and stored or made into powder form. In places where there is a limited land space for agriculture, the crop cannot be left indefinitely on the farm as it will not give room for utilization of the land for other crops. The use of plant ash in the storage of tubers by peasant farmers in Nigeria and other parts of the tropics has been a long standing practice, but the use of ash in cassava storage have not been quantitatively assessed. Many scientists have reported that in many African and Asian countries, it is a common practice to treat any cut or bruised portion of tubers with a paste of plant ash or with some other alkaline materials such as lime washing to reduce the probability of rotting or infection. This treatment has been shown to be substantially effective in reducing the incidence of rotting of stored tubers (Booth, 1974, Nemfor and Lyanga, 1987, Plucknet and White, 1979, Eze and Maduewesi 1990 a and b). According to Olorunda, (1979), Numfor and Lyonga, (1987), tubers are often covered with wood ash during storage and they suggested that the ashes might have pest static properties. Jackson et al. (1979) reported that benomyl (Benlate) reduced the level of rotting and increases the level of marketability of cocoa-yam corms in storage. It is not certain from previous reports whether plant ash and lime could be employed effectively to preserve cassava tubers after harvesting. The aim of this study is to find out the status of plant ash materials (oil palm inflorescence ash and orange peels ash) in preservation of cassava tubers and to compare the efficacy of the ashes with widely used fungicide
(Benlate) in reducing fresh weight loss and rotting of cassava tubers in storage. MATERIALS AND METHODS Freshly harvested cassava tubers (Manihot esculenta Crantz) were used for this experiment. Matured tubers of approximately uniform size (2.8 3.0kg) which were free from damage were selected and used for the study. One hundred and fifty tubers were employed and these were in three replicates of each treatment. Each replicate consisted of 50 tubers. The tubers were prepared by shaking off the adhering soil particles, removing all dirt and washing first with tap water before rinsing thoroughly with distilled water. Rinsed tubers were spread out to dry before applying the treatment. Treatment and their preparations: (Citrus sinensis) were collected, dried and burnt to ash, male and female inflorescences of oil palm trees (Elaeis guineensis Jacq) were also collected and burnt to ash. The paste of the two different ashes were prepared by suspending 400g of each plant ash in 1000ml of sterile distilled water and stirring it to form a paste (Eze and Maduewesi, 1990). Benlate was prepared at a concentration of 1000ppm with sterile distilled water. The storage was carried out in a shed constructed for the purpose at the back of the laboratory, Delta State University, Abraka Nigeria. The shed was made up of palm fronds and shaded from direct sun rays and fenced round with wire gauze to protect it from rodents. Raised platforms measuring 150cm high, 100cm wide and 500cm long each were used. Local mats made from Borasus fronds were used to cover the top of these platforms completely. Fifty tubers of cassava treated with the ash pastes of oil palm inflorescence, orange peels and Benlate solution were heaped on each platform. Three replicates of each treatment and the control were set up. The period of storage lasted for 8 weeks. The ph of the clear solution of each plant ash was determined using a ph meter. Determination of fresh weight loss: Each tuber was weighted before the treatment and at weekly interval after treatment for the period of eight weeks. The mean weight of each of the three replicates was obtained and the percentage loss in fresh weight was determined and calculated thus: Loss in fresh weight = Initial weight final weight %Loss in fresh weight =Loss in fresh weight X 100 Initial weight 1 Determination of rot incidence: Physical observations were made weekly to note the number of decayed tubers in each treatment. The observations were made for 8 weeks at weekly interval after the treatment. Percentage rot incidence was calculated thus: Number of tubers rotted X 100 Total number of tubers in the treatment 1 Determination of rot severity: The method of Eze and Maduewesi (1990a) was employed. The rot severity was determined for each tuber in which rot had developed. This was carried out by cutting such tuber longitudinally into two halves and the fraction of the rotted tissue determined by direct measurement. This was done by measuring the two perpendicular diameters of the rotted tissues and the average diameter taken. From these measurements, the percentage of rotted tissue was obtained. Rot severity was recorded on the following index. 0 = No rotting 1 = Very mild rotting (Less than 5% of tuber rotted) 2 = Mild rotting (6 10% of tuber rotted) 3 = Moderate rotting (11 25% of tuber rotted) 4 = Severe rotting (26 50% of tuber rotted) 5 = Very severe rotting (more than 50% of tuber rotted) RESULTS The cassava tubers lost weight progressively over the storage period. There was variation in weight loss which was influenced by the various treatments (Table 1). Loss in fresh weight was least in tubers treated with ash paste from oil palm inflorescence and highest in the control tubers. From the results obtained, loss in fresh weight of tubers treated with the plant ash pastes was significantly lower than that from the Benlate and control (P=0.05). Tubers treated with oil palm inflorescence ash paste recorded between 3.4 and 7.9 percent fresh weight loss while the tubers treated with ash pastes from orange peels and Benlate ranged between 4.1 to 8.8 and 0.2 to 13.3 percent respectively after 8 weeks of storage. (Table1) 2
Rot did not occur in tubers treated with ash pastes from oil palm inflorescence and orange peels until after 5 weeks in storage while rot started in control tubers after 3 weeks of storage (Table 2). The results showed that all the plant ash pastes and Benlate had significantly less rot incidence than the untreated tubers (p = 0.05). Table 1: Effect of oil palm inflorescence ash, orange peels ash and Benlate on the fresh weight loss of cassava tubers during 8 weeks of storage. Mean Percentage weight loss / per week. Treatment ph 1 2 3 4 5 6 7 8 Control 0.2 6.2 6.7 8.2 91. 10.2 12.1 13.3 Oil Palm Inflorescence ash 9.90 0.0 3.4 3.9 4.5 6.1 6.8 7.6 7.9 Ash 9.60 0.00 4.1 4.3 5.4 7.2 7.9 8.1 8.8 Benlate 0.00 4.6 4.9 5.7 8.1 8.8 9.1 9. Each value is a mean of 3 replicates. Table 2: Effect of oil palm inflorescence ash, orange peels ash and Benlate on cassava tubers rot during 8 weeks of storage. Mean Percentage weight loss /per week. Treatment 1 2 3 4 5 6 7 8 Control 0.00 0.00 0.00 25.00 30.00 40.20 45.60 75.10 Oil Palm Inflorescence ash 0.00 0.00 0.00 0.00 0.00 0.00 15.10 20.40 Ash 0.00 0.00 0.00 0.00 0.00 12.20 20.40 25.60 Benlate (1000PPM) 0.00 0.00 0.00 0.00 10.10 15.30 24.50 26.80 Each value is a mean of 3 replicates. Table 3: The effects of oil palm inflorescence ash, orange peels ash and Benlate on severity of rot development in cassava tubers during 8 weeks of storage. Rot severity index/wk Treatment 1 2 3 4 5 6 7 8 Control 0 2 2 3 3 4 4 4 Inflorescence ash 0 0 0 0 0 0 1 2 Ash 0 0 0 0 0 1 2 3 Benlate (1000PPM) 0 0 0 0 0 0 3 4 Rot severity index was based on the scale 0 = No rotting 1 = Very mild rotting 2 = Mild rotting 3 = Moderate rotting 4 = Severe rotting 5 = Very severe rotting 3
The results also showed that tubers treated with ash paste from oil palm inflorescence have the least rot severity index scores after 6 weeks of storage. Control tubers were almost or completely rotted after 6 weeks of storage (Table 3). Generally, all treatment had significantly lower rot severity Index scores than the control. The ash pastes from oil palm inflorescence and orange peels proved better than Benlate in preservation of cassava tubers for 8 weeks. It is however worthy of note that the cassava tubers became corky and loose freshness after 2 week of storage particularly in control tubers. The results of the ph determination showed that the plant ashes had a ph of 9.6 and 9.9. This indicated that the plant ash pastes were highly alkaline. The plant ash from oil palm inflorescence had higher ph value of 9.9 (Table 1). DISCUSSION Observations from this study have shown that ash pastes from oil palm inflorescence and orange peels were effective in reducing fresh weight loss and rotting of cassava tubers for a period of 8 weeks. The ash pastes proved better than the Benlate fungicide. Of the two plant ash pastes used, oil palm inflorescence was better than orange peels ash paste. This observation is in line with the reports of Coursey, (1967), Noon, (1978), Williams, (1986) and Eze Maduewesi, (1990a) who reported that wood ash pastes and filtrates from some plants including oil palm were effective in protecting yam tubers in storage against rot diseases. It has also been reported by Golob and Webley (1980) that wood ash successfully protected grains from insect damage during storage. In Nigeria, and many other tropical countries, it is a common practice by the peasant farmer to cover their tubers with wood ash during storage (Numfor and Lyanga, 1987, Olumide, 1979). The effectiveness of these ash pastes in reducing fresh weight loss of tubers in storage may be due to their effect in enhancing suberization of any wounded surface or exposed surface such as that created by detachment of the tubers from the stem thereby reducing the extent of water loss from the surface due to evaporation (Jackson et al. 1979, Noon, 1978). Palm inflorescence ash paste also proved more effective in reducing rot development than orange peels ash paste and Benlate fungicide (1,000ppm). Benlate has been reported to be a good fungicide in reducing fungal rot of yams and cocoyam in storage (Ogundana 1972, Ogundana and Dennis, 1981). In this study, the two different ash pastes from oil palm inflorescence and orange peels were more effective than Benlate. This has led to suggestion that plant ash might be pesticidal in action(numfor and Lyonga, 1987). The ash pastes used were strongly alkaline with their ph falling within a very narrow range from 9.6 to 9.9 which would suggest that the observed differences in the efficacy of the ash pastes might not be due to ph differences. Further studies are required to determine the active principles in these ash pates and their mode of action. CONCLUSSION: The results of this study showed that palm inflorescence and orange peels ashes could be used in practical control of loss of fresh weight and storage rot of tubers in storage. It also confirms the common use of ash pastes to store tubers in the Tropics. REFERENCES Booth, R. H. (1974). Post-harvest deterioration of Tropical root crops: Losses and their control. Trop. Sci: 49 63 Coursey, D. G. (1967). Yam storage 1: A review of yam storage practices and information of storage loses. J. Stored Products Res. 2: 229 243 Eze, C. S. and Maduewesi, J. N.C. (1990a). Relationship of Traditional Methods of Storage to the Magnitude of storage losses of Cocoyam (Colocasia esculent (L) Schott) Niger. J. Pl Prot. 13: 72 80. Eze, C. S. and Maduewesi, J. N.C. (1990b). Comparative Efficacy of Benlate, Lime and Plant Ash Treatment in Controlling Fresh Weight Loss, Sprouting and Rotting of Cocoyam (Colocasia esculenta (L.) Schott) in Storage Niger. J. Pl Prot. 13: 81 89 Golob. P. and Webley, D. J. (1980). The use of plants and minerals as traditional protectants of stored products. Trop. Prod. Inst. Rep: G. 138: 32pp Hahn, S. K. and keysor, J. (1985). Cassava: A basic food of Africa. Outlook on Agriculture 14: 95 100 IITA International Institute of Tropical Agriculture (1985). Screening Germplasm of Roots and Tuber crops for Nematode Resistance. Root and Tuber Improvement Programme. Research Highlights 1981: 32 33. Jackson, G. V. H., Gollifer, D. E. Pinigar, J. A. and NewHook (1979). The use of fungicide against postharvest decay in stored taro in the Solomon Islands. In: Small-Scale processing and storage of tropical root crops (Plunkneth, D. L.. ed) West view Trop. Series No 1 West view Press, Boulder, Colorado, pp 130 149. 4
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