Chemical insecticides have long been considered means of controlling crop pests. Although their effectiveness is obvious, their impact on the environment is increasingly discussed.. The objective of this study is to determine the agro-ecological component of a biological insecticide based on Aloe Vera in a Sahelian context. For this, an experimental device (randomized complete block with 3 repetitions and 4 block treatments) was set up to experiment with Aloe barbadensis as a bio insecticide on okra pests, so the data was collected through a grid. observation and monitoring of parameters. he results obtained show that the level of damage is significantly high in the control treatment T0 (63%) compared to the other treatments, i.e. 29% for the treatment T1, 7% for T2 and 1% for T3. Furthermore, as regards the number of leaves, 4 leaves attacked out of 6 were recorded at treatment T0, 1 leaf attacked out of 9 at treatment T1 and 0 leaves attacked at treatment T2 and T3. Thus, we can say that the pests were more dominant in the control T0 on all the parameters studied than in the other treatments and the results were negative in all the control treatments (T0). On this, aloe Barbadensis formulated as a biological insecticide in this experiment was found to be very effective against okra pests.
Research Article
Evaluation of the Effectiveness of a Natural Insecticide Based on Aloe barbadensis Against Pests of Abelmochus esculentus for the Promotion of Ecological Agriculture (Far-north Region -cameroun)
https://doi.org/10.21203/rs.3.rs-2614349/v1
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Aloe Vera
Okra
Biological Insecticide
Aloe emodin
Maroua.
Demographic expansion and economic growth experienced by the countries of the world have pushed farmers towards intensive production in order to meet the food needs of the population and eradicate the famine that is raging in the regions (Tamgno et al., 2013). The use of synthetic insecticides has been the cause of many environmental and public health problems, especially since the risks inherent in some of them are poorly assessed (Thakore, 2006).
However, the use of biological insecticides varies from one region of the world to another. In Cameroon, the use of biological insecticides is a technology to be promoted, as an alternative fight against the main insect pests and parasitic diseases (Kosma, 2013). Because indeed, biological insecticides contribute to preserving biodiversity (eliminates the nuisances linked to synthetic insecticides: pollution of groundwater or surface water, fauna and man), reduces the negative impact of agriculture on water quality (Deravel, 2014)
. More specifically in the Far North, we are seeing a rush towards organic production through the use of biological insecticides against crop pests (Kosma, 2014). Indeed, these poisonings were accompanied by dermatological symptoms (itching, tingling, burning of the skin, rash, wounds, complete destruction of the contaminated part), respiratory (tingling, burning and itching of the respiratory tract, difficulty breathing and coughing), ocular (burning conjunctivae, visual disturbances, stinging and burning in the eyes, loss of vision), gastrointestinal (abdominal pain, nausea, vomiting), headaches and dizziness to the point where, in some cases, loss of knowledge of the addict (Boni, 2017). It is in view of this state of affairs that it is urgent that we resort to organic farming with the use of natural inputs: hence the interest of this study.
Material
The material refers, among other things, to the study area, to any instrument, tool, software and materials used for the completion of this work. Aloe Barbadensis Miller: Aloe Barbadensis Miller or Aloe Bapensis is the main material of the formulated biological insectide because it was used for the manufacture of our biological insecticide because of the effectiveness of its gel and its availability (see Picture1).
- The Biological insecticide: The biological insecticide formulated in this experiment was made from Aloe Barbadensis Miller, which is a powerful variety of Aloe Vera because of its many virtues, its resistance and its effectiveness in the face of pest attacks. It has allowed for this purpose to protect plants against pest attacks, to control, repel, limit or even kill insect pests of okra thanks to its active ingredient aloe-emodin gel contained in aloe vera. Aloe-emodin is a bitter-tasting, yellow-brown substance found in the gel of at least 68 species of aloe at concentrations ranging from 0.1 to 6.6% of dry leaves and 3 to 35 wet leaves (Thakore, 2006). It is an irritating stimulant of the digestive tract, with anti-insecticidal, antifungal, antibacterial, hepato-protective, antiviral and anti-tumor properties (Deravel, 2014).
Okra (Abelmoschus esculentus): Abelmoschus esculentus, commonly known as Okra, is a species of tropical flowering plant native to Africa and Asia, close to the hibiscus. It was used in this experiment as an indicator of the efficacy of the formulated biological insecticide.
- A KERN BMX1 digital scale: to measure the mass of the raw material (aloe vera) to be used.
- A BLENDER brand Moulinex: which made it possible to grind the aloe vera and extract the biological insecticide in its raw state.
- Three graduated burettes: allowed to measure in milliliters the different doses of the biological insecticide formulated.
- A 16 Liter sprayer and an 11Liter watering can: use to spray the biological insecticide on the plants and water them.
The softwares
Microsoft Word software was used in this work for entering data collected in the field. Excel and SPSS software were used to process the data and present the results in table and graph form; merge information from multiple sources, plot simple or complex data and their analyses.
Méthodology
To be able to achieve our objectives, we opted for a holistic method because it takes into account several parameters such as the manufacture of the biological insecticide, the realization of the okra crop and the treatment of the okra plants with the biological insecticide formulated for the primary data, Literature research and literature review for secondary data.
Data collection
The collection of raw data and documentary research was the most important phase of this research. The data collected on the experimental site are of two types (primary and secondary).
Secondary Data
The collection of secondary data is the decisive phase of this research. Before the multiple field trips, the mobilization of the literature around the theme made it possible to have a oriented and precise idea thanks to the writings of other researchers. The documentary research was made possible thanks to the sources of information resulting from the reading of theses, memoirs, reviews, articles, books and scientific patents related to the effectiveness of biological insecticides. These documents were consulted via downloading on the internet and specifically in digital libraries (National Library of France), the website, journals and journals specializing in scientific production (Google Scholar, Caliga, Cairn Info, Science Direct and Scirus).
Primary Data
-Cultivation of okra
A prospective descent on February 29, 2022 in the field was carried out in order to have a precise idea of the reality on the ground before any sampling. This made it possible to have a substantial knowledge on the nature of the soil, the previous crops which was maize, the dimensions of the experimental portion and the layout of the different compartments. The cultivation of okra began after the choice of the experimental site and that of the plant material used of local origin (okra seed) from the slaughterhouse market in the city of Maroua. On March 1, 2022, the measurement of the dimensions of the experimental portion with a decameter tape measure (dm) was taken, so the surface is 56m², i.e. a length of 7m and a width of 8m. After this stage, this site was secured by acacia branches (see board 1).
- Soil Préparation, plant and watering
The field maintenance work took place on March 03, 2022 in the experimental site in Domayo and consisted of weeding and subdividing the plot into 12 compartments in equal proportion so the length of each compartment measured 1.5m and the width 1,7m. The distance between the aisles was 38cm delimited by a string and the stakes. Subsequently, the racks were amended with 100kg of organic compost allocated to the 12 racks (area of 56 square meters) to fertilize the soil, hoe with the hoe and water abundantly with a watering can, then left for three days, watering every morning for the microorganisms to come into contact with the soil. One week after the soil preparation work and the protection of the experimental unit, the sowing in pockets of 3 okra seeds per bucket every 40 cm between the sowing lines and 20 cm between the pockets.
- Labeling of lockers
One month after emergence, we made 12 plates to identify the percentages of the different doses of treatments of the formulated biological insecticide to be applied to the plants. To this end, the experimental device that was adopted for this experiment is a complete randomized block so we have 3 repetitions and 4 block treatments (see board 2).
with :
T0 : witness ; T1 : Aloe vera treatment at 50ml T2 : Aloe vera treatment at 100ml
T3 : Aloe vera treatment at 150ml
-Manufacture of the biological insecticide
The manufacturing process of the biological insecticide was done following (07) seven steps presented below:
• Choice and preparation of the raw material
It is a step that consists in choosing among the varieties of Aloe vera that exist, Aloe Barbadensis Miller which is a variety known and used by all because of its effectiveness, its gel and its availability. The nurseries of the latter were purchased from a gardener and planted in the shade and watered until their maturity (04 months) then used for the manufacture of the biological insecticide (picture 2).
Grinding of Aloe barbadensis miller and extraction of the raw biological insecticide
Once matured, 3 leaves of this plant are cut at each treatment, and weighed (400g) on a KERN BMX1 brand electronic scale and cut into small pieces using a knife and finally ground in a Moulinex of mark BLENDER for 5 minutes. After grinding, the product obtained is transferred to a container, then filtered using a cloth to extract the liquid (raw biological insecticide). The board below sufficiently illustrates this step (photo 3).
• Quantification of treatment doses
The various tests as well as the quantification of the biological insecticide solution were carried out in the laboratory of the Maroua Technical School of Agriculture (ETAM). Using burettes graduated at 100ml, 200ml and 250ml; the different treatment doses were quantified at 50ml of the active ingredient corresponding to the 1st treatment (T1), 100ml to the 2nd treatment (T2) and finally 150ml which correspond to the 3rd treatment (T3) (see picture 3).
The concentration of these different treatment doses in (g/L) which will be diluted in 1L of water is obtained according to the general formula:
C: represents the concentration of Aloe vera ground in the raw state in (g / L)
m: represents the mass of Aloe vera in (g)
V: represents the volume of a treatment (L)
So the concentration of treatment T1 (50 ml) is: 8 g/L, that of treatment T2 (100ml) is: 4 g/L and that of treatment T3 (150 ml) is: 2.6 g/L .
Dilution and obtaining the formulated biological insecticide
After formulation of the biological insecticide and quantification of the different treatment doses in millilitres, each quantified biological insecticide solution is diluted in 1L of water and applied with a sprayer for the treatment of plants (see photo 4).
The diagram below illustrates the detailed process for the manufacture of a biological insecticide based on aloe vera:
- Parameter tracking
Watering the plants
The frequency of watering the okra plants after sowing was done at an interval of every 5 days with 50L of water per tray until the appearance of the 4th leaf on the plant because at this stage, the plant needs water in average quantity followed by weeding after every 7 days. After the appearance of flowers, watering was abundant and regular every three (3) days.
Plant treatment
After identification of the compartments by plates, the treatment of the plants was done every 3 days thanks to the experimental device in randomized complete block set up for this experiment (see Fig. 2). The treatment of the plants was done every 3 days in the morning because just after the plants emerged, the attacks started directly and the pests were much more present on the leaves of each compartment and some on the other parts of the plant.
Tracking Settings
Parameters for monitoring the behavior of pests as well as the evolution of plant growth, after application of the manufactured biological insecticide, are recorded using the observation and treatment monitoring grid. This step consisted in labeling six (6) plants per compartment on which we noted the parameters above every seven (7) days. Thus, these parameters are among others: the average length of the plant and that of the leaves, the total number of leaves and the number of attacked leaves, the number of fruits, the level of damage, the number of flower buds and at the end observation. The compilation of all this information will make it possible to understand the effectiveness of the biological insecticide formulated with aloe vera.
Data processing
The data processing phase is a set of manipulations that consists of preparing the collected data, with a view to making them ready and usable.
Secondary data
The compilation of documentary data after collection, was carried out by classification of themes dealing with questions of the effectiveness of a biological insecticide as a whole, then those involved in the management of crop pests, and finally those involved in the evaluation of the efficacy of aloe barbadensis formulated as a biological insecticide for the control of okra pests.
Primary data
The processing of primary data consists of making usable information in different forms collected in the field. This is the sorting of the data collected which was done according to the passages on the ground.
Data analysis
The quantitative and qualitative data from the observation and treatment monitoring grid were analyzed and sorted, then processed and analyzed with software such as: Microsoft Word for entering data collected in the field; Microsoft Excel for data interpretation and diagram construction; SPSS for statistical tests of correlation, correspondence and hypothesis.
04 treatments T0 (0ml), T1 (50ml), T2(100ml) and T3(150ml)) of biological insecticide based on Aloe Barbadensis were highlighted on okra pests leading to a very specific result according to the analysis of well-defined parameters.
Effect of biological insecticide treatments on leaves
The Fig. 2 below showing the number of sheets shows us that:
- Treatments T1 (50ml), T2 (100ml) and T3 (150ml) are not significantly attacked compared to the control treatment T0 (0ml).- T3 and T2 are significantly different from treatments T0 and T1 for the number of total leaves.
- Treatment T0 had 4/6 attacked leaves, T1 had 1/9 while T2 and T3 each recorded 0 attacked leaves. It could therefore be that the T2 and T3 treatment did not record any attacked leaves because of certain parameters such as heat (unfavorable to the development of pests in the environment) and the constant watering which obviously made it possible to capitalize on the potential of the active ingredient of this Aloe emodin against pests.
However, we realize that in the months of March, April and May, the heat is much stronger therefore watering is frequently carried out; which pushes the pests to migrate to the untreated traps, which is why more damage is recorded at T0. The plate below supports the previous result by showing the significant difference in the quality of the leaves obtained.
Effect of the biological insecticide on the number of flowers and fruits We observe through figure A of the board below that:
- It was only at week 4 that there was flowering in treatments T2 (1) and T3 (1). This justifies the absence of biological insecticide at T0 and a low dose at T1 treatment;
- On the other hand, in the 5th week, flowering continues, with treatments T2 (3) and T3 (3), and begins at T0 and T1 (3).
Figure B of the same plate shows us that it is only week 5 that there is fruit formation. We observe on average 1/3 fruit at T1, 2/3 fruit at T2 and T3. The difference is not significant between the number of flowers and the number of fruits formed between the T2 and T3 treatments, but otherwise the T3 treatment has better fruiting. On the other hand, at T0 there is no flower that has evolved into fruit. This result is explained by the fact that the control treatment was not based on the biological insecticide, and that the attack of the insects had an impact on the fruiting at the T0 and T1 treatment.
We can also put forward the idea of the formulation of the biological insecticide at different doses. It had a positive effect on insect pests, thus favoring a better effect with T2 and T3 treatments, but also due to the influence of heat on pests because in April the heat was strong and the more treatment was applied these insects migrated to the untreated traps, which increased the damage in the T0 traps (see plank 6).
It is evident that the quality of the okra obtained looks very good. This aspect is obviously due to the effectiveness of the applied biological insecticide.
Effects of the biological insecticide on the level of pest damage
The figure below shows sufficiently that as the treatments were applied, less pest damage was seen on certain plants.
The diagram above shows us the level of damage of all the treatments. More damage is recorded at treatment T0 with a percentage of 63%, followed by T1 with 29%, then T2 with 7% and at the end of T3 with 1%. From this result it appears that the T3 treatment (1%) is more effective compared to the other treatments because a slight damage was recorded at the level of the latter. Whereas in the control treatment (T0) the level of damage is significantly high (63%) certainly because of the absence of the biological insecticide at this level, but also because of the heat which was much stronger in March and April therefore watering is frequently carried out; which pushes the pests to migrate to the untreated traps, which is why more damage is recorded at T0.
According to the work of Boni et al (2017), pesticide plants can be a promising alternative for the management of bioaggressors in market garden crops. However, most of them are not cultivated. However, people need to be made aware of the long-term benefits of products treated with plant-based pesticides to facilitate their use. The use of pesticide plants turns out to be an ancestral practice in Africa. Indeed, many plants are known and used for their biocidal activities (toxic, repellent, anti-feedant) against a wide range of bioaggressors. They can be used in the form of plant extracts for leaf protection (Mochiah et al., 2011; Mondédji et al., 2014a) or in combination with other crops (Asare-Bediako et al., 2010; Baidoo et al. ., 2012). The results obtained in this research are therefore acceptable because a significant difference was noted between the control and the treated traps. However, the work of Rabo et al (2021), corroborates these results in that, according to these assertions, the biopesticides even if they did not have the best yield in pods and seeds, reduced the damage of the pests and diseases on cowpea leaves, pods and inflorescences. At the end of this study, we can recommend to producers the use of biopesticides with more accentuated losses than with chemical pesticides but which can be compensated by the cost/benefit ratio. He adds by specifying that certain pests are also interested in the flowers of which they cause the abortion. The effectiveness of the treatments applied should result in the reduction or reduction of observable damage to the pods.
Therefore, the results of Mariam et al, (2015) working on T. urticae, lay the foundations for the use of pesticides in experimental fields because, clearly indicate that the pesticides tested allow effective control of T. urticae but are, for the most part, not very compatible with its predatory mite P. persimilis, if the latter is not usually in contact with these products. This gives meaning to this research. In addition, the parameters studied seem to be satisfactory in terms of the effectiveness of the bioinsecticide highlighted with okra pests because for Agbéko et al (2018), the percentage of leaves attacked and the percentage of leaf area damaged by the insect have were significantly affected by the treatments. It appears from this study that B. Bassiana and Suneem can be used to effectively control populations of okra flea beetles, Podagrica Spp in field conditions. The efficacy of the treatments differed significantly with Cypermethrin treatment leading to the best reduction in the population of flea beetles followed by Suneem and B. bassiana. Compared to the control plots, the damage associated with the pest's feeding behavior (leaf attack and defoliated leaf area) is significantly low in the treated plots. The results showed that when the okra plants received insecticide treatments based on cypermethrin and suneem, no statistical difference was obtained either in terms of attacked leaves and damaged leaf area. The manufactured bioinsecticide would then be more effective if it is added to the neem leaves; moreover, the work of Gougbe et al (2021), on the aqueous extracts of Euphorbia balsamifera and Azadirachta indica produced more tops than grains. Further research is needed to characterize these substances and possibly improve their pesticidal effectiveness.
Completed this work on the evaluation of the effectiveness of a biological insecticide based on Aloe vera (Aloe barbadensis) against okra pests (abelmochus esculentus) for the promotion of ecological agriculture in the region from the Far North of Cameroon, it was a question of showing that with an insecticide obtained with natural and local ingredients, we can fight effectively against pests. To this end, it appears that the phytosanitary product obtained and having been the subject of our study, proves to be very effective in the fight against crop enemies. In addition we found that, of these 4 treatments T3 (150ml of biological insecticide) is the most effective dose on all parameters with a non-significant level of damage of 1%. But on the other hand, T0 (control treatment) is the least effective dose on all the parameters with a significant level of damage, therefore 63%. The T2 and T1 doses are moderately effective. Thus the most effective dose against okra pests for 56m² of surface is T3.
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Pictures 1-3, Planks 1-6 and Photos 3 and 4 are available in the Supplementary Files section
No competing interests reported.
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Picture 1: Aloe Barbadensis Miller
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Picture 2: Aloe Barbadensis Miller
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Picture 3: Grinding of Aloe barbadensis and extraction of the raw biological insecticide • Quantification of treatment doses
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Plank 1: Sizing and layout of lockrs in the experimental site
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Plank 2: Culture Media Experiment Plan (A) Okra Rack Labeling (B)
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Plank 5: Representation of the evolution of the number of flowers (A) and the number of fruits (B) according to the weeks and the treatments
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Plank 6: Flowers (A) et fruits(B) good quality in the treated lockers
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Photo 3: Quantification of treatment doses
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Photo 4: Biological insecticide ready for use (A) and Treatment of the okra field (B)
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Photo 4: Non treated leaves (A) treated leaves with biological insecticide (B)
