Abstract: Background and Objective: Currently, the application of chemical pesticides and fertilizer in chili production is widespread due to the increasing demand for chili. Therefore, this study aimed to determine the potential of neem extract as a biopesticide application on the growth performance, pest severity and post-harvest parameters of chili plants. Materials and Methods: The study was performed using neem extract with four concentrations (0, 25, 50 and 75%) and a commercial chemical pesticide applied on chili plants. The pre-harvest parameters observed included pest severity, plant height, stem diameter, crown diameter, number of flowers, number of chili pods and Absolute Growth Rate (AGR) while the post-harvest parameters measured were fresh and dry weights of chili, leaf area, color, firmness and soluble solid concentrations. Results: The results indicate that all of the chili pre-harvest performance was found to be highly significant different (p<0.01) with concentrations. Application of 25% neem extract resulted in the lowest pest severity and higher performance of pre-harvest parameters. For post-harvest parameters, two parameters showed significant differences between the concentrations treatments at the 0.05 level which were firmness and leaf area. The chemical pesticide indicated the highest firmness while for leaf area application; the 25% neem extract indicated the highest result. Conclusion: The application of 25% neem extract resulted in better performance for pre-harvest parameters of chili compared to the chemical pesticide and other concentrations of neem extract while for post-harvest; only two out of six parameters indicated a significant difference.
INTRODUCTION
Chili (Capsicum annuum L.) belongs to the family of Solanaceae and is cultivated throughout the year as a cash crop. In Malaysian cooking, chili is one of the most important ingredients and commonly used either in the green or red ripe stage; depending on the utilization. There are many factors that can cause low productivity of the chili crop such as adverse climate, poor quality seeds, diseases and plant pests1. Plant pests, especially insects can attack the chili plant at different growth stages. Pest’s attacks on chili plants have frequently led to extreme and unselective usage of several insecticides by farmers which caused substantial environmental pollution and health hazards. In addition, pest resurgence problems will eventually increase the cost of production and the number of pesticides used and eventually giving unsatisfactory yield1. Although insecticidal interventions can reduce the pest population, it indirectly increases the pesticide residues in the fruits. The incidence of pesticide residues has seriously affected many chili exporters who failed to meet international trade regulations2.
The application of chemical fertilizer has become an effective method to increase production while the chemical pesticide effective as a pest controls method in the agricultural sector. In order to reduce the hazardous impacts on humans and the environment, the use of natural resources such as biofertilizer and biopesticides is highly recommended for food safety. An increase in demand for biopesticides reflects the growing public awareness of the impacts of chemical pesticides. The contents of biopesticides are less harmful to nature while being able to give more specific effects to the targeted pests3. Biopesticides that use plant extracts have recently shown great potential due to the low-price, having no residual effects, being environmentally friendly and highly toxic against major pests such as thrips, aphids, jassids, whiteflies and mites4. Botanical pesticides have the advantage of their rapid degradation and lack of persistence and bioavailability in the ecosystems that have been major issues in synthetic pesticides5.
Producers, particularly organic farmers, are looking for less toxic and efficient alternatives for conventional pesticides because no chemical pesticides are permitted in this production system. In addition, neem trees are widely planted as a landscape plant and are easily found in both villages and cities in Malaysia. This study was conducted to determine the effects of different concentrations of the neem extract application on chili, based on pre- and post-harvest parameters.
MATERIALS AND METHODS
Study area: This experiment was conducted from June-October, 2019 at the Rhu Tapai Agricultural Centre, Terengganu, Malaysia, latitude (5°30'48.6"N and longitude of 102°58'38.5"E). The plot size was 13×30 m and the chili seeds (Hybrid-461) were supplied by Farmers’ Organization Authority, Kuala Terengganu. A total of 50 chili seeds were sown in a sowing tray for a month, before being transferred to the field using an open fertigation system. The space between plants was 90×90 cm and arranged in a Randomized Complete Block Design (RCBD) which encompassed 10 replicates. This study followed the manual for chili fertigation practice issued by the Malaysian Agriculture Research and Development Institute (MARDI), except for the application of pesticides.
Application of neem extract and chemical pesticides: In this study, the treatments involved were four concentrations of neem extract, namely 0, 25, 50 and 75% also the commercial chemical pesticide. For neem extract preparation, neem leaves were collected from the Tok Jembal village and were brought to the laboratory at Universiti Malaysia Terengganu. All of the leaves were washed under running tap water and kept under the shade for air drying for two days. Then, a total of 200 g of freshly dried neem leaves were mixed with 1 L of deionized water and homogenized in a Panasonic MX-SM1031 blender. The mixture was filtered through a muslin cloth and the extract was left for 24 hrs in the refrigerator before being diluted into 25, 50 and 75% to a final volume of 1 L6. All of the neem solutions were sprayed onto the chili plants from the bottom to the top with an average dosage of 50 mL for each plant. For the chemical pesticides, a commercial brand commonly used by farmers in Malaysia was selected which was the Zesban EC Chlorpyrifos 21.2%. Exactly 2.4 mL of this chemical pesticide was diluted with deionized water to 1 L and sprayed to the whole part of the chili plants with an average dosage of 50 mL per plant.
Data collection: The parameters measured for this study encompassed the pre- and post-harvest parameters. Pre-harvest parameters were plant height, stem diameter, crown diameter, number of flowers, number of chili pods and pest severity. All of the data except the number of flowers and the number of chili pods were taken every two weeks after planting. The number of flowers and chili pods was counted once it appeared on the chili plants. The scoring of pest severity is shown in Table 17.
| Table 1: Pest severity scale used to access pest infestation on chili plant | ||
| Score | Pest infestation (%) | Severity |
| 0 | 0 | No pest infestation |
| 1 | 1-25 | Scattered appearance of a few pest on the plant |
| 2 | 26-50 | Severe infestation of pest on any one branch of the plant |
| 3 | 51-75 | Severe infestation of pest on more than one branch or half portion of the plant |
| 4 | 76-100 | Severe infestation of pest on the whole plant |
The last parameter measured for pre-harvest parameter was Absolute Growth Rate (AGR). AGR is the rate of increase in growth variable at time ‘t’. To measure AGR, the differential coefficient of growth variable with respect of time ‘t’ was calculated. In this study three growth variables were calculated by using following Eq.8:
where, P1, P2 refer to the growth variable (cm) at the time T1 and T2, respectively. AGR is expressed in cm/week.
Statistical analysis: Data were analyzed using factorial analysis of variance (ANOVA). For post-harvest parameters such as fresh and dry weights of chili, leaf area, color, firmness and soluble solid concentrations were determined in the laboratory after harvesting. The statistical analysis was performed using IBM SPSS statistic software version 20.0, IBM Corp, Armonk, USA.
RESULTS
Pre-harvest performance: Table 2 showed the effects of neem extracts on the pre-harvest parameters. The 25% of neem extract indicated the lowest mean level of pest severity which was only 0.73 (low level of pest infestation) followed by neem 75% (1.79), neem 50% (1.81) and application of no pesticide (2.19). Meanwhile, chili plants applied with the chemical pesticide resulted in the highest pest severity (2.69). Chili plants with the application of 25% neem extract as biopesticide was found to have the highest plant height (33.00 cm), followed by application of 50% neem extract (32.05 cm), 75% neem extract (30.63 cm) and 0% neem extract (27.64 cm). However, application of the chemical pesticide was found to produce the lowest plant height (25.27 cm).
In the present study, application of 25% neem extract as biopesticide had resulted in the biggest stem diameter (7.74 cm) while the application of chemical pesticide had resulted in the smallest stem diameter (6.56 cm) as compared to control (6.53 cm). The result for crown diameter had shown some contrast where the highest was indicated by chili plants with no pesticide application (29.06 cm). Chili plants with application of 25% neem extract had the second highest crown diameter (28.80 cm), followed by chili treated with chemical pesticide (27.38 cm) and 75% neem extract (26.18 cm).
The highest number of flowers (10.4 flowers) was found on chili plants applied with 25% neem extract, followed by application of no-pesticide (9.68), 50% neem extract (8.21) and chemical pesticide (7.3). The application of 75% neem extract was found to slightly lower the number of flowers. The number of chili pods was the highest when the chili plants were applied with 25% neem extract (17.53), followed by treatment with 50 and 75% neem extract (16.43 and 15.8, respectively). The chemical pesticide produced the second lowest number of chili pods while the application of no pesticide produced the least number.
Table 3 shows the analysis of Absolute Growth Rate (AGR). As noted in the table, only height indicated a significant effect at p<0.01 and the highest AGR for height was chili plants applied with 25% neem extract (4.42 cm per week), followed by 50% neem extract (4.04 cm per week) and the lowest was chemical pesticide (2.79 cm per week). For crown diameter, even though no significant different indicated, but application of 25% still noted the highest absolute growth rate of crown size.
Post-harvest performance: By referring to Table 4, there were three parameters that showed significant differences between the pesticides’ treatments at the 0.05 level. The parameters were firmness, leaf area and number of chili pods. For firmness, the highest mean was indicated by the chemical pesticide treatment. This was followed closely by treatment with 75% neem, 25% neem, control and lastly, 50% neem extract (8.06, 7.35, 5.26 and 4.97 N, respectively).
Data on the leaf area showed that the highest result (969.37 cm) was indicated by chili plants applied with 25% neem extract followed by application of 50% neem extract (903.60 cm), no pesticide (892.50 cm), chemical pesticide (813.81 cm), with the lowest leaf area produced by the 75% neem extract (760.34 cm).
| Table 2: Effects of neem extracts on the pre-harvest parameters | ||||||
| Neem extract/chemical pesticide | ||||||
| Attributes | No pesticide |
25% neem |
50% neem |
75% neem |
Chemical |
p-value |
| Pest severity | 2.19±0.097b |
0.73±0.097b |
1.81±0.097c |
1.79±0.097c |
2.69±0.097a |
0.000* |
| Plant height (cm) | 27.64±0.427c |
33.00±0.427a |
32.05±0.427a |
30.63±0.427b |
25.27±0.427d |
0.000* |
| Stem diameter (cm) | 6.53±0.178b |
7.74±0.178a |
7.65±0.178a |
6.58±0.178b |
6.56±0.178b |
0.000* |
| Crown diameter (cm) | 29.06±0.798a |
28.80±0.798a |
25.03±0.798c |
26.18±0.798bc |
27.38±0.798ab |
0.000* |
| Number of flower | 9.68±0.711ab |
10.40±0.712a |
8.21±0.713bc |
5.56±0.714a |
7.30±0.715cd |
0.000* |
| Number of chili pod | 11.50±0.803b |
17.533±0.803a |
16.433±0.803a |
15.80±0.803a |
13.433±0.803b |
0.000* |
| *Same letter in the same row for each factor, are not significantly different at p<0.05, ±: Standard error, *Significant at p<0.01 | ||||||
| Table 3: Summary of analysis of variance for the AGR of chili plant | |||
| Mean | |||
| Descriptive | Height AGR |
Stem AGR |
Crown AGR |
| 0% neem | 3.08±0.1cd |
1.08±0.04 |
3.8781±0.28 |
| 25% neem | 4.42±0.32a |
1.21±0.07 |
4.3100±0.37 |
| 50% neem | 4.04±0.18ab |
1.47±0.10 |
3.3263±0.023 |
| 75% neem | 3.61±0.13bc |
0.91±0.08 |
3.4575±0.048 |
| Chemical pesticide | 2.79±0.26d |
1.09±0.11 |
3.1019±0.038 |
| ANOVA (between pesticides) | ** |
ns |
ns |
| **Significant at p<0.01, ns: Not significant, alphabets showing different significant level | |||
| Table 4: Effect of neem extract on post-harvest performance of chili | ||||||
| Pesticide | Color |
Firmness (N) |
SSC (Brix) |
Leaf area (cm2) |
Fresh fruit (g) |
Dry fruit (g) |
| Non pesticide | 38.19±0.76 |
4.97±1.20ab |
7.53±0.09 |
892.50±67.77ab |
403.48±87.15 |
90.84±13.36 |
| Neem 25% | 37.46±0.87 |
5.26±0.66ab |
7.40±0.06 |
969.37±30.22a |
552.12±75.83 |
138.01±18.96 |
| Neem 50% | 37.72±2.60 |
3.27±0.75b |
7.37±0.09 |
903.60±0.15ab |
492.72±38.51 |
123.18±9.63 |
| Neem 75% | 36.45±0.45 |
7.35±1.35a |
7.27±0.03 |
760.34±9.89c |
445.25±52.60 |
110.99±12.91 |
| Chemical pesticide | 38.59±0.41 |
8.06±0.63a |
7.40±0.10 |
813.81±16.27bc |
464.84±88.11 |
116.24±22.02 |
| ANOVA(between pesticides) | ns |
* |
ns |
* |
ns |
ns |
| *Significant at p<0.05, ns: Not significant | ||||||
DISCUSSION
In general, pests that attack chili trees may consist of aphids, mites and trips where these pests will suck the liquid from the leaves, or damage the fruit and other parts of the tree. The direct effect of thrips attacks is the establishment of a shiny silvery color on the underside of the leaves and later on it will turn into brownish. The most severe attack on plants was the appearance of metabolic process disorders, which causes the leaves malformation to become curly and wrinkled9. Approximately 35% of chili plants in the field, 14% in storage and around 50% in total crops are lost each year due to attacks by insects and pests which adversely impact world crop production during the growing season, harvesting and storage10.
The use of botanical products is considered an appropriate practice for the management of pests between several specific approaches. Examples of common and already commercialized botanical pesticides derived from plants are pyrethrum (Chrysanthemum cinerariifolium), sabadilla (Schoenocaulon officinale) and tobacco (Nicotiana tabacum)11. The primary active compound, azadirachtin, occurs predominantly as a feeding deterrent and a growth retardant of more than 200 pests12. Commercially formulated neem oil and Azatrol applied to cucumber leaf disks at field recommendation rates induced potent feeding inhibition by S. eridania13. Azadirachtin had a moderate efficacy on hydroponic cucumber (56 and 69%) against Aphis gossypii and Tetranychus urticae, respectively14. Current study noted 25% of neem extract indicated the lowest mean level of pest severity which was only 0.73 (low level of pest infestation) Meanwhile, chili plants applied with the chemical pesticide resulted in the highest pest severity (2.69). This result supports the use of plant extracts as a good pesticide to keep the infection rate under control. This finding is supported by another study15, revealed that the number of infected plants increased rapidly in plots without application of phytopesticides compared to plots applied with phytopesticides. The lower infection rates may be due to the effects of phytopesticides on the virus vectors or directly on the disease itself. The antifeedant and repellent efficacy of neem leaves where enrichment of organic fertilizers with neem leaf powder and boiler ash was observed, to significantly improve resistance of plants against infestation by aphids16.
If there are fewer pest attacks, commonly the plant will be healthier and grow better. This current study supports the statement where chili sprayed with 25% neem extract showed the lowest pest severity and indicated highest growth performance compared to other concentrations and chemical pesticides. Plants that are not disturbed by pests are generally healthier and resulting in higher rate of photosynthesis. Similarly, reported that growth parameters of tomato were significantly increased gradually once the plants were sprayed and irrigated with neem extract17. Neem-treated plants produced the highest yield and this could be due to the neem releasing nutrients such as nitrogen for rapid vegetative growth and fruit development18.
For post-harvest quality, the potential of neem extracts, especially the 25% neem extract in maintaining the quality of post-harvest parameter for chili plants as compared to chemical pesticides. Refers to the fresh weight and dry weight of chili, although not showing significant differences but the weight of both still indicates the use of 25% neem gives the highest weight. Although biopesticides are said to give a beneficial effect on the tree, too high a concentration may change the beneficial function to the toxin and have a negative effect on the tree. Therefore, studies on appropriate concentration rates of biopesticides are essential.
CONCLUSION
The results of this study have shown that the application of 25% neem extract on chili plants can enhance pre- and post-harvest parameters of chili plants such as pest severity, height, stem diameter, number of chili pods, firmness and leaf area. This indicated that the 25% neem extract can be used as a biopesticide to increase pest resistance, growth performance and quality of post-harvest parameters of chili plants compared to a chemical pesticide commonly used by farmers in Malaysia. At the same time, the application of chemical pesticides can be reduced to ensure the sustainability of the yield and the environment.
SIGNIFICANCE STATEMENT
This study discovered the potential of neem extract that can be beneficial to enhance the growth performance and post-harvest quality of chili. This study will help the researchers to uncover the critical areas of chili production that can help to reduce the post harvest losses that many researchers were not able to explore.
ACKNOWLEDGMENT
Authors appreciate to Universiti Malaysia Terengganu for the funding under the grant research (TAPE-RG), Vote No. 55154.