Evaluation of the Insecticidal Properties of Two Plant Powders and Extracts for Protecting Wheat Grains Against Tribolium Castaneum (Herbst) [Coleoptera: Tenebrionidae]

Received 07 Feb, 2025

Accepted 11 Mar, 2025

Published 13 Mar, 2025

Background and Objective: Plant-based insecticides are widely recognized for their cost-effectiveness and eco-friendly properties in protecting stored grains. During storage, various insect pests target stored grain products, with Tribolium castaneum being one of the most destructive. The objective of this study is to evaluate the insecticidal properties of two plant powders and their extracts in protecting wheat grains against Tribolium castaneum infestation. Materials and Methods: This study observed the efficacy of Ricinus communis and Senna alata leaf powders and extracts in managing T. castaneumunder laboratory conditions at 28±2°C and 75±5% relative humidity. The powders were tested at dosages of 0.2, 0.4, 0.6, 0.8, and 1.0 g per 20 g of wheat grains, while the extracts were applied at concentrations of 0.1, 0.2, 0.3, 0.4, and 0.5 mL per 20 g. Parameters examined included mortality rates, lethal doses (LD₅₀ and LD₉₀), progeny suppression, weight loss percentage, seed damage, and the Beetle Perforation Index (BPI). One-way ANOVA and probit analysis were used to analyse the data gotten from the experiment. Statistical differences are determined when p<0.05. Results: The findings revealed that R. communis powder achieved 50% adult mortality at 1.0 g per 20 g of wheat grains within one day, whereas S. alata powder caused 60% mortality at the same rate. Similarly, the extract of R. communis at 0.5 mL per 20 g induced 76.67% adult mortality after one day, while S. alataextract achieved 86.67% mortality under the same conditions. Each plant’s powders and extracts effectively inhibited egg-laying, progeny production, weight loss, and seed damage. Among the two, S. alata demonstrated superior efficacy in both powdered and extract forms. Conclusion: Incorporating R. communis and S. alata into pest management strategies can significantly reduce the economic impact of T. castaneum, ensure the availability of viable seeds for planting, and enhance food security in Nigeria and other developing countries.

INTRODUCTION

Stored grains, cereals, and their derivatives serve as essential food sources globally, with maize, rice, and wheat ranking among the most widely consumed grains. Wheat grain (Triticum spp.) is a major staple food that contributes around 20 percent of the protein and energy in the world’s diet¹. Wheat serves as an excellent feed source for polygastric animals because of its high protein values as compared to other feed grains like maize or barley².

Insect pests are the leading cause of both qualitative and quantitative losses in stored grains globally, with losses ranging from 10 to 40%^3,4. Among these, the rust-red flour beetle (Tribolium castaneum, Coleoptera: Tenebrionidae) is particularly damaging, contributing to weight reductions of up to 40%⁵. Tribolium castaneum is a cosmopolitan pest and both larvae and adults can cause significant damage on the germ layer of wheat grains, their complete life cycle usually takes between 40 to 90 days, and adults can breed throughout the year in the tropics and subtropics⁶.

Tribolium castaneum is a major post-harvest and storage pest of wheat, maize, millet, sorghum and barley, females lay between 300-400 eggs in their 5-8 months of adult lifespan and under optimum conditions of 35^°C and 60-80% relative humidity⁷. Larvae emerge from the egg in approximately 3 days and spend an average 13 days causing significant damage to grains before becoming pupa⁸.

Organophosphates, pyrethroids, and fumigants have been employed to control T. castaneum populations; however, their effectiveness is hindered by the accumulation of toxic residues in food, high costs, and adverse effects on non-target organisms⁹. Another problem is insects developing resistance against a variety of synthetic insecticides over time. This led to proffering an alternative means for the control of red-rust flour beetle. Hence, the use of natural plant extracts, which aims at the elimination of the problems posed by the use of synthetic chemicals. Natural plant extracts are recognized as cost-effective, safe for humans, and environmentally friendly alternatives for pest control⁵. Some plant products have been evaluated for their toxic effects against stored grain pests, these plants are largely available in the environment¹⁰. Little information is available worldwide about the use and development of organic pesticides which proffer the same levels of control to beetles as synthetic insecticides. There are needs for current research to be aimed at the insecticidal efficacies that may be present in these plant products to combat the increasing problem of T. castaneum infesting wheat grains

MATERIALS AND METHODS

Study area: The study was carried out at the Department of Biology, Federal University of Technology, Akure, Ondo State. The study was carried out between May, 2022 to October, 2023.

Insect cultivation: Adult red rust flour beetles (T. castaneum) were obtained from the Storage Entomology Research Laboratory, Department of Biology, Federal University of Technology, Akure (FUTA), Nigeria. A total of 100 beetles were introduced into a 1 l glass jar containing 500 g of wheat grains sourced from a grain merchant in Akure metropolis, Ondo State, Nigeria. The beetle culture was maintained in an insect rearing cage under controlled conditions of 30±2°C and 75±5% relative humidity.

Identification and sex differentiation: The identification and sex determination of T. castaneum were conducted at the Entomology Research Laboratory, Department of Biology, FUTA. The pupal stage of the insect was placed on a slide and examined under a binocular microscope (Olympus CX23) to observe the sex characteristics. Genital papillae on the ventral side of the distal abdomen segment were used to determine the sexes. The female pupae possess a developed, protruding and pointed genital papillae compared to males¹¹.

Collection of plant material: The leaves of R. communis and S. alata were collected along Ondo Road in Akure, Ondo State. The plants were authenticated by a Plant Taxonomist from the Department of Crop, Soil, and Pest Management, FUTA. The leaves were air-dried in the Biology laboratory and ground into a fine powder using an electric blender (Philips HR2114). The powdered material was then sieved through a 1 mm² mesh. The resulting fine powders were stored in air-tight plastic containers and kept in a refrigerator at 4°C to preserve their quality before use.

Collection of wheat grains: The wheat grains used in this study were obtained from the Agricultural Development Programme, Ministry of Agriculture and Rural Development, Akure, Ondo State. The grains were first cleaned to remove debris, straw, and chaff, and sorted to eliminate broken grains. They were then sterilized by storing them in a deep freezer at -°C for 7 days to kill any existing insect eggs and larvae. This procedure was necessary as all insect life stages, including eggs and larvae, are susceptible to low temperatures¹². After disinfestation, the wheat grains were placed in a Gallen Kamp oven (model 250) at 40°C for 4 hours and then air-dried in the laboratory for 72 hrs to prevent mould growth⁹. The grains were subsequently stored in plastic containers with tightly sealed lids.

Extractions of plant material: Ethanol extracts of R. communis and S. alata leaves were prepared using the cold extraction method. Approximately 300 g of the plant powders were separately soaked in 600 mL of absolute ethanol in an extraction bottle. The mixture was stirred occasionally with a glass rod, and extraction was allowed to proceed for 3 days. Afterward, the mixture was filtered through a double layer of Whatman No. 1 filter paper, and the solvent was evaporated using a rotary evaporator at 30-40°C and a rotary speed of 3-6 rpm for 8 hrs¹³. Any remaining solvent was removed under vacuum with the rotary evaporator (Labo therm SW 200). The concentrated extract was then air-dried to eliminate any residual ethanol.

Insect Bioassay
Toxicity of plant powders on adult mortality and adult emergence of T. castaneum: The 20 g of clean, uninfested wheat grains were measured using an electronic weighing balance (Model JTC 2101N) in the laboratory and placed in 250 mL plastic cups. Next, 0.2, 0.4, 0.6, 0.8, and 1.0 g doses of R. communis and S. alata leaf powders were carefully weighed and mixed separately with 20 g of the clean wheat grains. The plastic cups containing the powder and grains were shaken thoroughly to ensure proper mixing. Then, five copulating pairs (5 males and 5 females) of newly emerged adult T. castaneum (less than four days old) were introduced into each plastic cup containing the treated wheat grains and covered with muslin cloths. The control group contained only 20 g of wheat grains and five copulating pairs of adult T. castaneum (without any plant powder). Insect mortality was assessed daily for 5 days. Dead beetles were those that did not respond to a pin probe (i.e., failure to react to a sharp pin). At the end of the 5-day treatment period, the percentage of adult mortality was calculated using Abbott's formula¹⁴:

Where:

	PT	=	Corrected mortality (%)
	PO	=	Observed mortality (%)
	PC	=	Control mortality (%)

The weight loss of the maize grains was calculated as the percentage loss in weight using the following formula¹⁴:

The number of damaged maize grains was assessed by calculating the percentage seed damage using the following formula¹⁴:

Beetle Perforation Index (BPI) was expressed as described by Ileke et al.¹⁵:

BPI value exceeding 50 was regarded as enhancement of infestation by the beetles or negative protectability of the powders and extracts tested.

Toxicity of ethanolic extracts on adult mortality and adult emergence of T.castaneum: Twenty grams of clean, uninfested wheat grains were weighed into 250 mL plastic containers. Then, aliquots of 0.1, 0.2, 0.3, 0.4, and 0.5 mL of R. communis and S. alata leaf extracts were measured using a graduated syringe and mixed with the 20 g of wheat grains in the plastic containers. The mixture was thoroughly stirred using a small glass rod. The plastic containers were left open for 40 min to allow the ethanol solvent to evaporate. Following this, five copulating pairs (5 males and 5 females) of adult T. castaneum were introduced into each of the plastic containers, and the containers were covered with muslin cloths. Each treatment was replicated three times. The control group contained only 20 g of wheat grains and ten copulating pairs of adult T. castaneum (no plant extract was added in the control group). Insect mortality was assessed daily for 5 days. Dead beetles were those that did not move and did not respond to pin probing (failure to react to a sharp pin). After the 5-day treatment period, the percentage of adult mortality was calculated¹². The experimental setup was then kept in the insect rearing cage for an additional 35 days to allow new adults to emerge. The percentage of adult emergence, weight loss, seed damage, and Beetle Perforation Index were calculated as described above.

Data analysis: The data were analyzed using Analysis of Variance (ANOVA), and treatment means were separated using Duncan’s New Multiple Range Test. The ANOVA was conducted using SPSS 27.0 software and statistical significance was determined at p≤0.05.

RESULTS

Mortality response of adult T. castaneum treated with some plant powders: The mortality response of adult T. castaneum exposed to leaf powders from two plant species is shown in Table 1. Insect mortality increased with dosage, as higher concentrations resulted in greater mortality rates. The toxicity of the plant powders differed significantly from the control (p<0.05). Senna alata powder was the most toxic to Red rust flour beetle, the powder caused 16.67, 30.00, 40.00, 50.00 and 60.00% mortality of T. castaneum at concentrations 0.2, 0.4, 0.6, 0.8 and 1.0 g per 20 g of wheat grains after the first day of exposure, respectively. The least toxic plant powder was R. communis that caused 03.33, 13.33, 26.67, 36.67 and 50.00% mortality of T. castaneum at concentrations 0.2, 0.4, 0.6, 0.8 and 1.0 g per 20 g of wheat grains after the first day of exposure, respectively. Senna alata powder evoked 83.33 and 100% mortality of red rust flour beetle at rate 0.8 and 1.0 g per 20 g of wheat grains after fifth day of exposure, respectively. Toxicity trend of the two plant leaf powders was dosage dependent and exposure time.

Lethal dosage (LD) of some plant powders against adult T. castaneum: The lethal dose of the two plant leaf powders against T. castaneum is given in Table 2. The dosage calculated for the R. communis and S. alata leaf powders to cause 50% (LD₅₀) and 90% (LD₉₀) mortality against the test organism calculated after the first day were 1.03 and 2.90 g, 0.92 and 2.15 g, respectively. However, it was observed that these values continued to reduce after the second, third, fourth, and fifth days of exposure. From the calculation, S. alata leaf powder was observed to have the lowest lethal dose across all periods of exposure. All these values have different confidence limits that might be effective aside from the calculated values.

Table 1:

Mortality response of adult T. castaneum treated with some plant leaf powders

		Mortality % (Mean±SE)
Plant powder	Dosage (g)	Day 1	Day 2	Day 3	Day 4	Day 5
Ricinus communis	0.2	03.33±3.33a	13.33±3.33b	20.00±0.00b	30.00±0.00b	33.33±3.33b
Senna alata		16.67±3.33b	23.33±3.33b	33.33±3.33b	36.67±3.33b	43.00±3.33b
Ricinus communis	0.4	13.33±3.33b	20.00±0.00c	33.33±3.33c	36.67±3.33b	46.67±3.33c
Senna alata		30.00±3.33c	36.67±3.33c	46.67±3.33c	53.33±3.33c	56.67±3.33c
Ricinus communis	0.6	26.67±3.33c	36.67±3.33b	46.67±3.33d	53.33±3.33c	60.00±0.00d
Senna alata		40.00±0.00d	50.00±0.00d	56.67±3.33d	67.67±3.33d	73.33±3.33d
Ricinus communis	0.8	36.67±3.33d	50.00±0.00e	60.00±0.00e	66.67±3.33d	73.33±3.33e
Senna alata		50.00±0.00e	63.33±3.33e	70.00±0.00e	76.67±3.33e	83.33±3.33e
Ricinus communis	1	50.00±0.00e	60.00±0.00e	66.67±3.33e	80.00±0.00e	93.33±3.33f
Senna alata		60.00±0.00f	70.00±0.00e	76.67±3.33e	86.67±3.33f	100.00±0.00f
Untreated	0	0.00±0.00a	0.00±0.00a	0.00±0.00a	0.00±0.00a	0.00±0.00a
Each value is a Mean±Standard error of three replicates, Means followed by the same letter along the column are not significantly different (p>0.05) using duncan’s multiple range test

Table 2:

Lethal dosage (LD) of some plant leaf powders against adult T. castaneum

Plant powder	Exposure period	LD50 (LCL-UCL)	LD90 (LCL-UCL)
Ricinus communis	Day 1	1.03 (0.90-1.31)	2.90 (1.96-8.99)
	Day 2	0.90 (0.78-1.07)	2.12 (1.57-4.67)
	Day 3	0.78 (0.48-0.45)	2.20 (4.44-6.76)
	Day 4	0.75 (0.56-0.81)	1.44 (1.20-2.30)
	Day 5	0.68 (0.50-0.76)	1.12 (0.99-1.54)
Senna alata	Day 1	0.92 (0.41-1.18)	2.15 (1.92-1.28)
	Day 2	0.75 (0.41-0.93)	2.11 (1.52-7.86)
	Day 3	0.72 (0.33-0.90)	1.96 (1.39-7.81)
	Day 4	0.51 (0.01-0.84)	1.75 (1.30-2.10)
	Day 5	0.60 (0.00-0.72)	0.92 (0.99-1.54)
LD50: Lethal dosage at which 50% population response, LD90: Lethal dosage at which 90% population response, LCL: Lower Confidence Limit and UCL: Upper Confidence Limit

Number of adult emergence of T. castaneum in wheat treated with some plant leaf powders: Table 3 presents the effectiveness of R. communis and S. alata leaf powders in preventing the emergence of T. castaneum adults. The protective ability of both plant powders was significantly different (p<0.05) from the untreated control. The highest level of seed protection was observed at 0.8 and 1.0 g of S. alata and 1.0 g of R. communis powder, with no recorded adult emergence of T. castaneum. Additionally, the protective effect of 0.8 and 1.0 g of S. alata powder did not significantly differ from that of 1.0 g of R. communis powder, as all treatments recorded zero adult emergence. However, 0.6 g of R. communis powder (3.67 adult emergence) was significantly less effective (p<0.05) than 0.6 g of S. alata powder (0.66 adult emergence) in preventing T. castaneum infestation in wheat seeds. A significant difference (p<0.05) was also observed between 0.2 g of R. communis powder (8.00 adult emergence) and 0.2 g of S. alata powder (5.33 adult emergence), indicating a variation in their insecticidal effectiveness.

Protectant effect of some plant powders on wheat seed damage, weight loss, and beetle perforation index against red-rust flour beetle: Percentage seed damage, weight loss, and beetle perforation index were presented in Table 4. Wheat seeds treated with 0.2 g of R. communis and 0.2 g of S. alata powder gave 2.47, 1.70% seed damage, respectively. There was no significant difference (p>0.05) between the two plant leaf powders at 0.2 g. The highest percentage of seed damage was observed in wheat treated with 0.2 g of R. communis powder, recording 2.47% seed damage, which was significantly different (p<0.05) from the control (16.75%). The lowest percentage of seed damage was recorded in treatments with 0.8 g and 1.0 g of S. alata powder (0.0% damage) and 1.0 g of R. communis powder (0.10% damage).

Table 3:

Number of adult emergences of T. castaneum in wheat treated with some plant powders

Plant powder	Dosage (g)	Adult emergence
Ricinus communis	0.2	8.00±0.58d
	0.4	6.33±0.33cd
	0.6	3.67±0.33bc
	0.8	1.33±0.33b
	1	0.00±0.58a
Senna alata	0.2	5.33±0.88b
	0.4	2.33±0.33bc
	0.6	0.66±0.33a
	0.8	0.00±0.00a
	1	0.00±0.00a
Untreated	0	47.67±2.19e
Each value is a Mean±Standard error of three replicates. Means followed by the same letter along the column are not significantly different (p>0.05) using duncan’s multiple range test

Table 4:

Protectant effect of some plant powders on wheat seed damage, weight loss, and Beetle perforation index against red rust flour beetle

Plant powder	Dosage (g)	Total no. of seed	Number of seed of damage	Seed damage (%)	Weight loss (%)	Beetle perforation index
Ricinus communis	0.2	314.33	8.00±0.58d	2.47±0.17a	0.98±0.67c	15.53±0.49c
	0.4	311.67	6.33±0.33cd	1.98±0.10a	0.79±0.38c	12.70±0.90c
	0.6	311	3.67±0.33bc	1.14±0.09a	0.47±0.33b	7.32±0.66b
	0.8	313.67	1.33±0.33b	0.75±0.52a	0.30±0.21a	4.78±0.90b
	1	313.67	0.00±0.58a	0.10±0.18a	0.10±0.07a	0.70±0.70a
Senna alata	0.2	315.67	5.33±0.88b	1.70±0.30a	0.67±012c	10.83±1.18c
	0.4	316	2.33±0.33bc	0.72±0.11a	0.29±0.04b	4.67±0.86b
	0.6	314.67	0.66±0.33a	0.27±0.10a	0.80±0.40a	1.36±0.68a
	0.8	312	0.00±0.00a	0.00±0.00a	0.00±0.00a	1.26±1.26a
	1	316.33	0.00±0.00a	0.00±0.00a	0.00±0.00a	0.00±0.00a
Untreated	0	317.33	47.67±2019e	16.75±1.00b	12.80±0.00d	>50.00±0.00d
Each value is a Mean±Standard error of three replicates, Means followed by the same letter along the column are not significantly different (p>0.05) using duncan’s multiple range test

Their protective effect was not significantly different (p>0.05) from 0.8 g of R. communis (0.75%), 0.6 g of R. communis (1.14%), 0.4 g of R. communis (1.98%), 0.8 g of S. alata (0.00%), 0.6 g of S. alata (0.27%) and 0.4 g of S. alata (0.72%). The highest weight loss was recorded with wheat treated with 0.2 g of R. communis powder (0.98%); this was significantly different (p<0.05) from what was recorded from the untreated (12.80%). The beetle perforation index recorded from the seeds treated with 0.2 g of R. communis plant powder (15.53%) was the highest, followed by 0.4 g of the same powder (12.70%).

Mortality response of adult T. castaneum treated with some plant extracts: Mortality response of adult T. castaneum treated with two plants leaf extracts is presented in Table 5. Insect mortality is concentration dependent. The higher the concentration, the higher the mortality rate the toxicity of the plants extract was significantly (p<0.05) different from the control. Senna alata leaf extract was the most toxic to Red-rust flour beetle, the extract caused 46.67, 56.00, 70.00, 80.00 and 86.67% mortality of T. castaneum at concentrations 0.1, 0.2, 0.3, 0.4 and 0.5 mL per 20 g of wheat grains after the first day of exposure, respectively. The least toxic plant powder was R. communis that caused 26.67, 40.00, 56.67, 66.67 and 76.67% mortality of T. castaneum at concentrations 0.1, 0.2, 0.3, 0.4 and 0.5 mL per 20 g of wheat grains after the first day of exposure, respectively. Both R. communis and S. alata leaf extracts evoked 100% mortality of red rust beetle at a rate 0.4 and 0.5 g per 20 g of wheat grains after the fifth day of exposure, respectively. Toxicity trend of the two plant leaf extracts was concentration dependent and exposure time.

Table 5:

Mortality response of adult T. castaneum treated with some plant extracts

		Mortality % (Mean±SE)
Plant conc	Extract (mL)	Day 1	Day 2	Day 3	Day 4	Day 5
Ricinus communis	0.1	26.67±3.33b	36.67±3.33b	50.00±0.00b	56.67±3.33c	63.33±3.33b
Senna alata		46.67±3.33b	53.33±3.33b	60.00±0.00b	66.67±3.33b	73.33±3.33b
Ricinus communis	0.2	40.00±0.00c	46.67±3.33c	56.67±3.33b	66.67±3.33c	76.67±3.33c
Senna alata		56.00±3.33c	63.33±3.33c	73.33±3.33c	80.00±0.00c	90.00±0.00c
Ricinus communis	0.3	56.67±3.33d	66.67±3.33d	80.00±0.00c	86.67±3.33d	96.67±3.33d
Senna alata		70.00±0.00c	80.00±0.00d	90.00±0.00d	100.00±0.00d	100.00±0.00d
Ricinus communis	0.4	66.67±3.33e	76.67±3.33d	93.33±3.33d	100.00±0.00e	100.00±0.00d
Senna alata		80.00±0.00d	93.33±3.33e	100.00±0.00e	100.00±0.00d	100.00±0.00d
Ricinus communis	0.5	76.67±0.00f	90.00±0.00e	96.67±3.33d	100.00±0.00e	100.00±0.00d
Senna alata		86.67±0.00e	100.00±0.00e	100.00±0.00e	100.00±0.00d	100.00±0.00d
Untreated	0.0	0.00±0.00a	0.00±0.00a	0.00±0.00a	0.00±0.00a	0.00±0.00a
Each value is a Mean±Standard error of three replicates, Means followed by the same letter along the column are not significantly different (p>0.05) using duncan’s multiple range test

Table 6:

Lethal Concentration (LC) of some plant extracts against adult T. castaneum

Plant extract	Exposure period	LC50 (LCL-UCL)	LC90 (LCL-UCL)
Ricinus communis	Day 1	0.69 (0.42-0.84)	1.76 (1.35-4.03)
	Day 2	0.64 (0.50-0.73)	1.18 (1.02-1.60)
	Day 3	0.55 (0.45- 0.62)	0.88 (0.78-1.02)
	Day 4	0.43 (0.31-0.56)	1.64 (0.67-0.93)
	Day 5	0.35 (0.26-0.42)	0.55 (0.43-0.81)
Senna alata	Day 1	0.65 (0.38-0.80)	1.41 (1.12-2.77)
	Day 2	0.53 (0.42-0.60)	0.85 (0.75-1.01)
	Day 3	0.41 (0.28-0.55)	0.62 (0.43-0.89)
	Day 4	0.32 (0.21-0.52)	0.51 (0.32-0.78)
	Day 5	0.34 (0.15-0.41)	0.50 (0.41-0.67)
LC50: Lethal dosage at which 50% population response, LC90: Lethal dosage at which 90% population response, LCL: Lower Confidence Limit and UCL: Upper Confidence Limit

Lethal Concentration (LC) of some plant extracts against adult T. castaneum: Table 6 presents the lethal dose of the two plant leaf extracts against T. castaneum. The calculated dosages of R. communis and S. alata leaf extracts required to achieve 50% (LC₅₀) and 90% (LC₉₀) mortality after the first day were 0.69 and 1.76, and 0.65 and 1.41 mL, respectively. However, these values progressively decreased over the subsequent days of exposure. Analysis revealed that S. alata leaf extract consistently exhibited the lowest lethal concentration across all exposure periods. Additionally, the confidence limits indicate potential variations in efficacy beyond the calculated values.

Number of adult emergences of T. castaneum in wheat treated with some plant leaf extracts: According to the results presented in Table 7, the effectiveness of R. communis and S. alata extracts in preventing adult emergence of the Red-rust flour beetle, T. castaneum, was significantly different (p<0.05) when compared to the control. The highest level of seed protection was observed with 0.3, 0.4, and 0.5 mL of both R. communis and S. alata extracts, as no adult emergence was recorded in these treatments. The seed protection ability of 0.3, 0.4, and 0.5 mL of S. alata extract was not significantly different from that of R. communis extract, with no adult emergence in both cases. However, the protection provided by 0.2 mL of R. communis leaf extract (1.00) was significantly different (p<0.05) from the 0.2 mL of S. alata leaf extract (0.33) regarding adult emergence. There was no significant difference (p<0.05) between the protection abilities of 0.1 mL of R. communis (1.67 adult emergence) and 0.1 mL of S. alata leaf extract (1.33 adult emergence).

Protectant effect of some plant extracts on wheat seed damage, weight loss, and beetle perforation index against red-rust flour beetle: The data on seed damage percentage, weight loss, and beetle perforation index are summarized in Table 8. Wheat seeds treated with 0.1 mL of R. communis and 0.1 mL of S. alata extracts showed seed damage of 0.41 and 0.21%, respectively, with no significant difference (p>0.05) observed between the two plant extracts at this dosage.

Table 7:

Number of adult emergences of T. castaneum in wheat treated with some plant extract

Plant extract	Concentration (mL)	Adult emergence
Ricinus communis	0.1	1.33±0.33a
	0.2	1.00±0.33a
	0.3	0.00±0.00a
	0.4	0.00±0.00a
	0.5	0.00±0.00a
Senna alata	0.1	1.67±0.33a
	0.2	0.33±0.33a
	0.3	0.00±0.00a
	0.4	0.00±0.00a
	0.5	0.00±0.00a
Untreated	0	46.00±1.53b
Each value is a Mean±Standard error of three replicates, Means followed by the same letter along the column are not significantly different (p>0.05) using duncan’s multiple range test

Table 8:

Protectant effect of some spice’s powders on wheat seed damage, weight loss, and Beetle perforation index against Red-rust flour beetle

Plant extract	Conc. (mL)	Total no. of seed	Number of seed damage	Seed damage (%)	Weight loss (%)	Beetle perforation index
Ricinus communis	0.1	321.67	1.33±0.33a	0.41±0.10a	0.53±0.13a	2.52±0.61a
	0.2	314.67	1.00±0.00a	0.31±0.00a	0.40±0.00a	1.95±0.10a
	0.3	313	0.00±0.00a	0.00±0.00a	0.00±0.00a	0.00±0.00a
	0.4	317.67	0.00±0.00a	0.00±0.00a	0.00±0.00a	0.00±0.00a
	0.5	313.33	0.00±0.00a	0.00±0.00a	0.00±0.00a	0.00±0.00a
Senna alata	0.1	314.33	0.67±0.33a	0.21±0.10a	0.27±0.13a	1.36±0.68a
	0.2	314.67	0.33±0.33a	0.10±0.10a	0.13±0.13a	0.63±0.10a
	0.3	313.67	0.00±0.00a	0.00±0.00a	0.00±0.00a	0.00±0.00a
	0.4	313	0.00±0.00a	0.00±0.00a	0.00±0.00a	0.00±0.00a
	0.5	317.67	0.00±0.00a	0.00±0.00a	0.00±0.00a	0.00±0.00a
Untreated	0	317.33	51.67±2.02b	16.27±0.72b	6.51±0.50c	>50.00±0.00c

The highest seed damage was observed in wheat treated with 0.1 mL of R. communis extract (0.41%), which was significantly different (p<0.05) from the control group (16.27%). The lowest seed damage was recorded in wheat treated with 0.3, 0.4, and 0.5 mL of both R. communis and S. alata extracts, where no seed damage (0.0%) was observed. These treatments were not significantly different (p>0.05) from the 0.2 mL of R. communis (0.31%), 0.1 mL of R. communis (1.41%), 0.2 mL of S. alata (0.10%), and 0.1 mL of S. alata (0.21%). The highest weight loss was recorded in wheat treated with 0.1 mL of R. communis extract (0.53%), which was significantly different (p<0.05) from the control (6.51%). The beetle perforation index was highest in seeds treated with 0.1 mL of R. communis extract (2.52%), followed by 0.2 mL of the same extract (1.95%).

DISCUSSION

The findings of this study support the use of R. communis and S. alata leaf powders and extracts as effective methods for preserving wheat grains from degradation caused by storage insect pests. The treatments significantly reduced the ability of the red rust flour beetle to lay eggs on the protected seeds, which in turn led to a notable decrease in the extent of damage.

The results of this study demonstrated that the application of plant extracts successfully prevented 100% reproduction of the red rust flour beetle. The action mechanism may involve their antifeedant or repellent properties, which aligns with the findings of Saxena et al.¹⁶, who reported effective control of T. castaneum using Citrus reticulata and Psidium guajava leaves. Antifeedants are substances that hinder or disrupt insect feeding by rendering the treated materials unattractive or unpalatable¹⁷. The analysis of variance revealed that damage, including percentage grain weight loss and beetle perforation index (BPI), was significantly reduced or entirely prevented when the plant powders and extracts were used. Oil extracts are recognized for their efficacy in controlling insects across all life stages^18-20.

In this present study, S. alata leaf powder and extract had the lesser value of lethal dose and concentration of the two plant leaves used and this shows its more potent toxicity level on T. castaneum and while R. communis leaf powder and extract had the higher value of lethal dose and concentration of the two-plant product used, this show that it has lesser toxicity potency as compared to S. alata. In the course of this research, the mortality of adult insects increased with both the duration of exposure and the concentration gradient. S. alata was found to be more effective than R. communis on the adult T. castaneum at all tested concentrations after Day 1 of exposure.

Ileke and Oni²¹ found that treatment with Cassia alata extracts resulted in a reduction of certain metabolic enzymes in T. castaneum, including Acid PhosphaTASR/2025e, Alkaline PhosphaTASR/2025e, Glutamate Pyruvate Transaminase, Glutamate Oxaloacetate Transaminase, Lactate Dehydrogenase, and Acetylcholinesterase. This decrease in metabolic enzyme activity suggests disruption of the insect’s chemical pathways, leading to abnormal physiological states that impair their survival, as reported by Zeba and Khan¹⁸.

The present study result agrees with Ojo and Ogunleye¹⁹ who reported the insecticidal efficacy of Cassia alata against C. maculatus. The present study has shown that the S. alata leaf powders are more toxic to T. castaneum than R. communis. The high mortality observed in the insects could explain the ability of plant powders and extracts to prevent seed damage and weight loss effectively. This may be due to the inhibition of egg laying by the insects on the treated grains, which subsequently reduced larval feeding and consequently prevented seed damage and weight loss, as noted by Nath et al.²². In this study, the toxicity of the plant materials varied depending on the type of plant and exposure duration. The findings also indicated that the leaf extracts were more toxic to the insects compared to the leaf powders used for contact toxicity. This difference in effectiveness may be attributed to the concentration of active ingredients in the extracts during the extraction process, as suggested by Salah et al.²³. The high mortality rate of T. castaneum exposed to the powders and extracts could be linked to contact toxicity, as the treated seeds, covered by the powders and extracts, acted as a toxic source for the adult beetles after consumption. Additionally, the treated grains limited the insects’ feeding, thereby hindering their normal growth and development, which led to starvation and eventually the death of some insects, as reported by Deme et al.²⁴.

The evaluation of leaf powders and extracts in this study showed a significant reduction in seed damage and weight loss caused by T. castaneum. The leaf extracts exhibited higher toxicity than the powders, resulting in minimal to no seed damage or weight loss in treated wheat grains. Additionally, the Beetle Perforation Index (BPI) was nearly zero for most extracts at the tested concentrations. These results underscore the potential of plant extracts as viable alternatives to synthetic pesticides, as both extracts effectively suppressed insect reproduction across all applied dosages. As interest in botanical treatments for pest control grows, there is a need for continued development and refinement of these natural solutions using established scientific methods to control storage insect pests effectively.

CONCLUSION

The research study demonstrated the efficacy of using R. communis and S. alata, two natural plant products, in controlling T. castaneum on maize infestations. It was established that these botanicals could effectively reduce the damage caused to wheat grains by T. castaneum. Ricinus communis powder caused 50% adult mortality at 1.0 g per 20 g of wheat grains in one day, while S. alata powder achieved 60% mortality. The extracts at 0.5 mL per 20 g induced 76.67 and 86.67% mortality for R. communis and S. alata, respectively, effectively inhibiting egg-laying, progeny production, weight loss, and seed damage. Senna alata exhibited superior efficacy, highlighting the potential of both plants in pest management to protect seed viability and food security.

The use and further development of these bioinsecticides is highly recommended due to their rapid degradation in the environment compared to synthetic pesticides. Additionally, they are more accessible than many man-made insecticides and safer for beneficial pests than chemicals which remain in the environment for a longer time after application.

SIGNIFICANCE STATEMENT

This study discovered the efficacy of R. communis and S. alata as natural plant-based bioinsecticides that can be beneficial for controlling T. castaneum infestations in stored wheat grains. The findings highlight the potential of these botanicals as environmentally friendly alternatives to synthetic pesticides, offering a safer and more sustainable pest control solution. This study will help researchers uncover critical areas of botanical insecticide application and environmental impact that many researchers were not able to explore. Thus, a new theory on the role of plant-derived bioinsecticides in integrated pest management may be arrived at.

REFERENCES

1. Atta, B., M. Rizwan, A.M. Sabir, M.D. Gogi and M. Sabar et al., 2020. Toxic and repellent characteristics of some plant extracts used against Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) improve the grain quality of stored wheat. J. Innovative Sci., 6: 1-11.
2. Ahmad, F., N. Iqbal, S.M. Zaka, M.K. Qureshi and Q. Saeed et al., 2019. Comparative insecticidal activity of different plant materials from six common plant species against Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). Saudi J. Biol. Sci., 26: 1804-1808.
3. Fields, P.G., 2006. Effect of Pisum sativum fractions on the mortality and progeny production of nine stored-grain beetles. J. Stored Prod. Res., 42: 86-96.
4. Krishna, P.N. and U. Yadav, 2023. Efficacy of different plant extracts and insecticide on red flour beetle, Tribolium castaneum (Herbst) in Wheat, Triticum aestivum. Int. J. Environ. Clim. Change, 13: 508-513.
5. Ajayi, F.A. and S.A. Rahman, 2006. Susceptibility of some staple processed meals to red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). Pak. J. Biol. Sci., 9: 1744-1748.
6. Lougraimzi, H., S. El Iraqui, A. Bouaichi, S. Gouit, E.H. Achbani and M. Fadli, 2018. Insecticidal effect of essential oil and powder of Mentha pulegium L. leaves against Sitophilus oryzae (Linnaeus, 1763) and Tribolium castaneum (Herbst, 1797) (Coleoptera: Curculionidae, Tenebrionidae), the main pests of stored wheat in Morocco. Polish J. Entomol., 87: 263-278.
7. Haines, C.P., 1991. Insects and Arachnids of Tropical Stored Products: Their Biology and Identification (A Training Manual). 2nd Edn., Natural Resources Institute, Chatham, United Kingdom, ISBN: 9780859542821, Pages: 246.
8. Howe, R.W., 1965. A summary of estimates of optimal and minimal conditions for population increase of some stored products insects. J. Stored Prod. Res., 1: 177-184.
9. Adedire, C.O., O.M. Obembe, R.O. Akinkurolere and S.O. Oduleye, 2011. Response of Callosobruchus maculatus (Coleoptera: Chrysomelidae: Bruchinae) to extracts of cashew kernels. J. Plant Dis. Prot., 118: 75-79.
10. Isman, M.B., 2006. Botanical insecticides, deterrents, and repellents in modern agriculture and an increasingly regulated world. Annu. Rev. Entomol., 51: 45-66.
11. Udo, I.O., M.S. Ekanem and E.U. Inyang, 2011. Laboratory evaluation of West African black pepper (Piper guineense) seed powder against maize weevil (Sitophilus zeamais Mots.). Munis Entomol. Zool. J., 6: 1003-1007.
12. Abbott, W.S., 1925. A method of computing the effectiveness of an insecticide. J. Econ. Entomol., 18: 265-267.
13. Iram, N., M. Arshad and N. Akhter, 2013. Evaluation of botanical and synthetic insecticide for the control of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). BioAssay, 8.
14. Ashamo, M.O. and O. Akinnawonu, 2012. Insecticidal efficacy of some plant powders and extracts against the Angoumois grain moth, Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae). Arch. Phytopathol. Plant Prot., 45: 1051-1058.
15. Ileke, K.D., J.E. Idoko, D.O. Ojo and B.C. Adesina, 2020. Evaluation of botanical powders and extracts from Nigerian plants as protectants of maize grains against maize weevil, Sitophilus zeamais (Motschulsky) [Coleoptera: Curculionidae]. Biocatal. Agric. Biotechnol., 27.
16. Saxena, R.C., G. Jilani and A. Abdul Kareem, 1989. Effects of Neem on Stored Grain Insects. In: Focus on Phytochemical Pesticides, Jacobson, M. (Ed.), CRC Press, Boca Raton, Florida, ISBN: 9781351072052, pp: 97-112.
17. Rajashekar, Y., K.V. Ravindra and N. Bakthavatsalam, 2014. Leaves of Lantana camara Linn. (Verbenaceae) as a potential insecticide for the management of three species of stored grain insect pests. J. Food Sci. Technol., 51: 3494-3499.
18. Zeba and M.A. Khan, 1995. Effect of fenvalerate on protein and amino acid contents and enzyme activities in the Ostracod Chrissia halyi. Pestic. Sci., 45: 279-282.
19. Ojo, D.O. and R.F. Ogunleye, 2013. Comparative effectiveness of the powders of some underutilized botanicals for the control of Callosobruchus maculatus (Coleoptera: Bruchidae). J. Plant Dis. Prot., 120: 227-232.
20. Alabi, O.Y. and M.M. Adewole, 2017. Essential oil extract from Moringa oleifera roots as cowpea seed protectant against cowpea beetle. Afr. Crop Sci. J., 25: 71-81.
21. Ileke, K.D. and M.O. Oni, 2011. Toxicity of some plant powders to maize weevil, Sitophilus zeamais (Motschulsky) [Coleoptera: Curculiondae] on stored wheat grains (Triticum aestivum). Afr. J. Agric. Res., 6: 3043-3048.
22. Nath, R., G. Singh and G. Deep, 2019. Efficacy of some botanical extracts against Tribolium castaneum: Coleoptera (Tenebrionidae). Plant Cell Biotechnol. Mol. Biol., 20: 660-666.
23. Salah, S., M.H. Abass and A.A. Alyousuf, 2023. Repellency and phytoxicity assessment of plant extracts, essential oils and nanoparticles on Tribolium castaneum herbst beetles infesting wheat grains (Triticum estivum L.). Basrah J. Sci., 41: 276-310.
24. Deme, G.G., Y.D. Malann, E.S. Chundusu and J.A. Chup, 2019. Insecticidal effects of Cassia tora and Cassia alata against cowpea weevil (Callosobruchus maculatus). Sci. World J., 14: 144-147.