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Frontiers in Agronomy ·

Volume 8 - 2026 | https://doi.org/10.3389/fagro.2026.1900866

Field efficacy of Tephrosia vogelii leaf extracts against Aphis fabae Scopoli (Hemiptera: aphididae) on common bean (Phaseolus vulgaris)

  • Dominick Stephen Nana1*corresponding author
  • Paulo John Lyimo2
  • Ramadhani Omari Majubwa1
  1. 1Department of Crop Science and Horticulture, College of Agriculture, Sokoine University of Agriculture, Morogoro, Tanzania
  2. 2Department of Ecosystem and Conservation, Sokoine University of Agriculture, Morogoro, Tanzania
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Abstract

Common beans are one of the world’s most important crop to the small-scale farming communities in Sub-Sahara Africa. Common beans are vulnerable to a wide range of insect pest assaults such as aphis fabae. Tephrosia vogelii extracts to control insect pests is an eco-friendly solution that works well against Aphis fabae. LC MS analysis was used to confirm the presence of chemotype 1. Furthermore, crude extracts of the plant were taken and tested against Aphis fabae in the field. A randomized Complete Block Design with three replications and treatments with different concentrations of 2%, 4%, 8%,10%, 2.2%, 4.2%, 8.2%,10.2% for crude extracts, Cypermethrin 10% EC as a positive control and water as a negative control were employed. Four weeks after spray, 10.2% was recorded to have the lowest number of aphids per plant (2.33 ± 0.333), which was significantly different from the highest (67.0 ± 02.082) recorded from control treatments (p<0.05). Four weeks after spray, 8% exhibited the lowest leaf damage (0.7 ± 0.37), which was significantly different from the highest (2.3 ± 0.3) recorded from control treatments (p<0.05). Treated plots were significantly exhibited highest grain yield (kg/ha) compared to the control plots (p<0.05). Leaf damage and total yield exhibited a negative correlation (y = -272.98x + 1034.5) with r 2 = 0.80, aphid population density and leaf damage were positive correlated (y = 41.666x+42.006) with r 2 = 0.69. Tephrosia vogelii leaf extracts offer a sustainable, eco-friendly alternative to synthetic insecticides for effective Aphis fabae management and enhanced bean productivity. Field trial at large scale agriculture is suggested.

Keywords

1 Introduction

Common bean (Phaseolus vulgaris L.) is an annual leguminous crop belonging to the family Leguminosae, with pinnately compound trifoliate large leaves (Mwanauta et al., 2015). Common bean grains play big dietary role in supplying protein, dietary fiber, energy as well as micronutrients to millions of people worldwide (Yanda and Tryphone, 2023). More than 100 million households in Africa use common beans (Mukankusi et al., 2019). Common bean usually termed as a subsidiary-crop to be relied upon during food shortage or supplement diet as it is drought resistant crop and its ability to adapt well in semi-arid regions of the tropics (Swema and bvMwinuka, 2021). Despite its importance, the production of common beans is hindered by a complex of biotic constraints, including insect pests that have led to decline in quality and yields (Ogecha et al., 2019; Katungi et al., 2009). Prolonged droughts and severe insect pests’ infestation (Beebe et al., 2013) are among of the major challenges of common beans production. If left unchecked, insect pests can cause significant yield loss (Hillocks et al., 2006). Furthermore, in the context of developing countries such as Tanzania, the escalating threat of crop losses attributed to insect pests such as aphids, poses a direct challenge to food security (Nyukuri, 2019).

The black bean aphid, Aphis fabae Scopoli, is the one of the most destructive pest of common beans in Africa (Mwanauta et al., 2015; Hansen et al., 2008). Aphis fabae is widely distributed and has a diverse host plant range (Singh et al., 2017). Aphids are regarded as phloem-feeding insects that cause substantial damage to horticulture and agriculture globally due to feeding related damage and the transmission of economically important plant viruses (Goławska et al., 2023). Heavy infestations result in the accumulation of honeydew on leaf surfaces, promoting the growth of soty molds, interfering light interception and thus hinder photosynthesis (Nyukuri, 2019). Field studies have shown that yield losses may exceed 50% due to bean aphid infestation (Sayed et al., 2020).

Various methods of insect pest management have been used to protect crops from insect pest damage so as to increase crop production and enhance food security. In developing countries such as Tanzania aphid management depends largely on the use of synthetic pesticides (Kayange et al., 2019). The excessive use of chemical insecticides has resulted to negative human and environmental effects (Isman and Grieneisen, 2014) and increased resistance of insect pests against synthetic pesticides (Mwanauta et al., 2015). The use of synthetic pesticide formulations as a pest control strategy is problematic since local farmers may not always be able to afford, especially in remote areas where agriculture is the major source of revenue and food security (Gutierrez-Moreno et al., 2020).

Various plant species are rich sources of bioactive chemicals or secondary metabolites, making them valuable sources of insect control agents (Mkindi et al., 2019; Mkindi 2016). Studies have revealed that Tephrosia vogeliican be used as pesticide because it contained flavonoids, tannins, terpenoids, and saponins as pesticide secondary metabolites (Mlozi et al., 2022; Minja et al., 2002; Kayange et al., 2019). In addition to being inexpensive and readily accessible, T.vogelii can be processed using simple techniques suitable for small scale farmers, making it an attractive option for sustainable pest management and food security. The insecticidal efficacy of T.vogelii varies among chemotype, with T.vogelii chemotype 1 has high insecticidal potential when compared to the other chemotypes (Belmain et al., 2012). However, these chemotypes could be challenging to recognize and differentiate morphologically (Mkindi et al., 2019). Farmers might unknowingly utilize inefficient plant material as a result of variation of chemical makeup (chemotypes), which would have a negative impact on the spread and commercialization of botanical pesticides. The information about synergy of T.vogelii (chemotype 1) against A.fabae is still limited. Therefore, phytochemical characterization is essential for identifying elite T.vogelii plants with superior insecticidal properties. Thus, this study was designed to develop a low cost, ecofriendly aphids’ management strategy through the use of Tephrosia vogelii leaf extracts in Tanzania (Figure 1).

Picture of *Tephrosia vogelii*. Source: Nana et al., 2024.
Figure 1. Picture of Tephrosia vogelii. Source: Nana et al., 2024.

2 Materials and methods

2.1 Location

The study was conducted in Morogoro municipal located at latitude 5° 58” and 10° 0”to the South of the Equator and longitude 35° 25” and 35° 30” East of Greenwich. The Morogoro region has an area of 72–939 km2 and population of 3,197, 104 (National Bureau of Statistics, NBS, 2022). The area is predominantly a mountainous vegetation as well as miombo woodland (Figure 2). The region receives annual precipitation of about 600 to 1200 mm with mean annual temperature 18°C- 30°C in river valleys annually (Ministry of Planning, Economy and Empowerment, 2006).

Tanzania map showing the region where experiment was conducted.
Figure 2. Tanzania map showing the region where experiment was conducted.

2.2 Experimental design

The field was disc harrowed and ridged prior to planting. Randomized Completely Block Design, with 10 treatments in three replications was employed. Throughout this investigative endeavor, eight distinct concentrations of the leaf extracts were deployed; 2g/100ml, 4g/100ml, 8g/100ml, 10g/100ml, 2.2g/100ml,4.2g/100ml, 8.2g/100ml, 10.2 g/100ml (indicating extract weight in grams per 100ml of the extraction solvent). These weight/volume (w/v) concentrations corresponded to 2%, 4%, 8%, 10%, 2.2%, 4.2%, 8.2%, and 10.2% (w/v) obtained after extraction. These concentrations were deliberately chosen because T.vogelii is highly toxic even at minimal doses. The distilled water and Cypermethrin 10% EC served as negative and positive controls respectively. These doses were sprayed using hand sprayer started at early vegetative growth stage. Spraying was applied on a weekly basis (7 days interval) once aphid infestations had established on the crop as per small herders farmers’ practice. The plots were sprayed once a week for the period of four weeks. The synthetic insecticide followed the same schedule. To prevent the bio-pesticide degradation from exposure to sunlight and air, these applications were made either early in the morning or late in the evening. Experimental plots consist of 5m x 5m were used with 1 meter between them and between neighboring fields. Planting was done in a space of 20cm within rows X 50cm between rows. Two common bean seeds were planted per each hole and gap filling was done six days after seed emergence. Standard management practices were applied for all experimental plants.

2.3 Plant chemotype 1 identification and extraction of plant materials

Plant materials were chosen based on documented insecticidal activity of Tephrosia vogelii. Young and tender leaves were collected from different locations. The plant materials (leaves) were collected based on the presence of white flower as an indicator or criteria for chemotype 1 (Mkindi et al., 2019) in order to assure the selection of plant materials with strong insecticidal activity. To ensure uniformity, leaves from each collection were mixed together from each species before drying (Mkenda et al., 2015b). The plant leaves were manually harvested and transported to the drying shed in sacks in preparation for extraction process. Finely crushed leaves were extracted; they were submerged for 48 hours in dichloromethane solvents. Following evaporation, the final T.vogelii leaf extract was then maintained as a stock solution (100%) and storage until it was needed for the bioassay experiments. Liquid Chromatography Mass Spectrometry was used to confirm the presence of chemotype 1. Leaf extracts were analyzed via LC-MS to determine phytochemical composition, using a Thermo Fisher scientific U300 system with a Q-active APCI source in both ionization modes. The method involved 24-hour extraction, centrifugation, and 30-minutes FTMS analysis (m/z 300-700) using a 100mmx4.6mm RP-MS column with water/acetonitrile-formic acid elution (Figure 3).

Schematic extraction process.
Figure 3. Schematic extraction process.

2.4 Data collected

2.4.1 Aphids’ population number

A direct visual count method was used to estimate the aphid population (Makila et al., 2018). The aphids were counted in the morning since they are less active and simple to count with the help of magnifying lens. Five tagged different plants were randomly selected from each treatment so as to estimate the population of aphids. Counting started at early vegetative the first stage after first appearance of aphids. Scouting was assessed once weekly for four consecutive weeks before treatments application and again one week after spraying (Equation 1). One observer visually inspected and counted the aphids in each tagged plant three times using non destructively procedures, and the average number was then calculated (Figure 4). Aphids on bean plant were counted week before spray. Reduction of aphid population over control was calculated by formula proposed by Maji et al. (2015) in Equation 1.

Bean plant infested by bean aphids and Experimental plot preparation.
Figure 4. Bean plant infested by bean aphids and Experimental plot preparation.

(1) %ROC=MC−MTMC×100

%ROC = percentage reduction of aphid population density over control.

MC=Mean number of aphid population in control.

MT=Mean number of aphid population in treatment.

2.5 Damage assessments

Five randomly selected common beans plant from each of the inner four rows were used to visually assess the rate of severity of aphid leaf damage three times. Aphid leaf damage was defined as wilted and wrinkled leaves, crinkling in the middle vein, sooty molds and honeydew formation, stunted growth and curled leaves in each experimental unit. Data on leaf damage was collected weekly for a period of four weeks. A scale of 0–4 was used to score the degree of leaf damage severity; 0=no aphid leaf damage, 1 = light damage and infestation of less than 25% of the plant leaf, 2 = average leaf damage of 26% to 50%, 3 =high leaf damage of 51% to 75% of the plant leaf, and 4 =severe damage of more than 75% of the plant leaf, resulting in plants with high levels of infestation that had yellow and scaly leaves (Mkenda et al., 2015a) as highlited in Equation 2.

(2) %ROC=LC−LTLC×100

%ROC = % reduction of bean leaf damage over control.

LC=Mean leaf damage in control.

LT=Mean leaf damage in treatment.

2.6 Evaluation of yield

Yield parameters (without drying) such as the pod weight (g), pods number per plant, and the seeds number per pod were collected two weeks prior to the harvesting season. Five plants were selected at random for each plot, and pods number per plant was counted and recorded. In each plot, five pods were selected to measure weight of pod as well as counting number of seed per pod. Total yields (kg/ha) and 100 seed weights were measured using electric balance and recorded after harvest.

(3) Yield=Plot yield(kg)Plot size(m2)×10000

2.7 Data analysis

Aphid population, leaf damage across sampling time, common bean yield and yield parameters were subjected to analysis of variance (ANOVA) and mean comparison for treatments were done using least significant difference (LSD, P ≤ 0.05) using SAS software version 9.4. Regression analyses were performed on aphids,population density against leaf damage and total leaf damage against common bean yield using MS excel 2016.

3 Results

3.1 Chemotype 1 identification

Analysis of the leaf extracts of T.vogelii sample identified the presence of chemotype 1. Figure 5 shows the LC-MS chromatograms of chemotype 1 characterized by the presence of the rotenoids (rotenone) with retention time 10.96, corresponding to the relative peak intensity of 95%, indicating large abundances of rotenone in the T.vogelii sample.

Relative intensity as a function of retention time (first part), mass to charge ratio, m/z (second part), and fragmentation pattern of rotenone (third part) for a representative *Tephrosia vogelii* sample from Morogoro (Chemotype 1).
Figure 5. Relative intensity as a function of retention time (first part), mass to charge ratio, m/z (second part), and fragmentation pattern of rotenone (third part) for a representative Tephrosia vogelii sample from Morogoro (Chemotype 1).

3.2 Compounds identified from Tephrosia vogelii leaf extracts

A total of six compounds were identified from T.vogelii leaf extracts such as deguelin, isoquercitin, quercetin, rotenone, 6,4-dimethoxy-7-hydroxyiflavone, and glycetein (Table 1). LC-MS analysis confirmed the presence of chemotype 1 in the analyzed sample due to the presence of rotenoids such as deguelin.

Table 1. Compound identified in solvent leaf extracts of Tephrosia vogelii.

CompoundRTm/zFormulaCompound nameNature of the compounds
110.1394.13C23H22O6DeguelinIsoflavonoids
210.20284.1C16H12O5GlyceteinIsoflavonoids
311.00298.1C17H14O56,4-Dimethoxy-7-hydroxyisoflavoneIsoflavonoids
412.5464.10C21H20O12IsoquercitinFlavonoids
515.70302.03C15H10O7QuercetinFlavonoids
610.96395.1C23H22O6RotenoneIsoflavonoids

3.3 Aphid population across sampling time

There was a significant difference between treatments in terms of aphid population number (p ≤ 0.05; Table 2). Among T.vogelii leaf extracts treatments, 10.2% had the lowest number of aphids per plant after one and two weeks of spraying (21.33 ± 2.186 and 11.67 ± 1.202), respectively, which were significantly different (p<0.05) from the highest number of aphids per plant (66.00 ± 8.185 and 71.67 ± 2.848) respectively, recorded from the negative control treatments. Three weeks after spray, 10.2% exhibited the lowest number of aphids per plant (10.00 ± 2.082), which was significantly different (p<0.05) from the highest (70.67 ± 1.202) recorded from negative control treatments. Four weeks after spray, 10.2% exhibited the lowest numbers of aphids per plant (2.33 ± 0.333) which was significantly different from the highest (67.0 ± 02.082) recorded from control treatments. Comparatively, the positive control reduced aphid populations more effectively than the rest of treatments at four weeks post-spray (1.67 ± 0.882).

Table 2. Effect of Tephrosia vogelii leaf extract on adult counts of Aphis fabae per plant.

TreatmentWBS1WAS2WAS3WAS4WASCMROC%
T155.33± 0.882a42.67 ± 1.856a24.00 ± 0.577a20.33 ± 0.33a7.00 ± 1.000a23.566
T253.67± 2.667a35.33 ± 2.906ab20.00 ± 1.155ab17.00 ± 0.577ab4.67 ± .667ab19.2572
T350.00± 2.517a28.67 ± 1.202bc15.3 ± 3.180b14.67 ± 0.882bc2.67 ± 0.333b15.3478
T448.67± 6.333ab24.67 ± 2.603c15.33 ± 3.283bc12.67 ± 1.333bc3.33 ± 1.202b1480
T551.67± 4.372b30.00 ± 4.619bc21.67 ± 0.667ab18.67 ± 0.882a3.67 ± 1.667b18.573
T650.00± 3.464b27.67 ± 2.906bc19.67 ± 0.333ab14.00 ± 3.000c4.33 ± 0.333ab16.6776
T738.33± 2.9c24.33 ± 2.333c15.67 ± 1.764abc11.67 ± 1.202c3.33 ± 1.202b13.7580
T850.33± 4.91ab21.33 ± 2.186c11.67 ± 1.202bcd10.00 ± 2.082c2.33 ± 0.333b11.3384
T946.33± 3,53b10.33 ± 0.667e5.00 ± 0.577d3.00 ± 0.577d1.67 ± 0.882b593
T10Grand meanP value67.67± 4.33d51.20.00766.00 ± 8.185f31.10.00171.67 ± 2.848f220.00170.67 ± 1.202e19.270.00167.0 ± 02.082d100.00168.84

Values are expressed as Mean ± SEM of three replicates. Values with the same alphabet within the same row are not significantly different. CM, Cumulative mean, WBS, Week before spray, WAS, Week after spray, TVE; Tephrosia vogelii leaf extracts, %ROC, Percentage reduction over control.

T1=2% TVE; T2 = 4% TVE; T3 = 8%TVE; T4 = 10% TVE; T5 = 2.2%TVE, T6 = 4.2%TVE; T7 = 8.2%TVE; T8 = 10.2% TVE, T9=Synthetic pesticides, T10=Water only.

3.4 Bean leaf damage severity across sampling times

Leaf damage differed significantly among treatments (p ≤ 0.05). However, no significant difference in term of bean leaf damage were recorded among treatments after one week of spray (p>0.05; Table 3). Among Tephrosia vogelii leaf extracts after one week of spray, 10% showed the lowest leaf damage (1.2 ± 0.12), while the highest leaf damage was recorded from control treatment (2.3 ± 0.33). Also, after two weeks of spray, 10% exhibited the lowest leaf damage (1.07 ± 0.07), which was significantly different from the highest (2.3 ± 0.33) recorded in the control treatments (p<0.05). Three weeks after spray, 10.2% exhibited the lowest leaf damage (1.27 ± 0.1) among leaf extracts, which was significantly different from the highest (2.03 ± 0.09) recorded from the control treatments (p<0.05). However, four weeks after spray, 8% showed the lowest leaf damage per plant (0.7 ± 0.37), which was significantly different from the highest (2.3 ± 0.3) recorded from control treatments (p ≤ 0.05). Comparatively, positive control (Cypermethrin 10%EC) consistently provided the greatest reduction in leaf damage throughout the sampling period (p ≤ 0.05; Table 3).

Table 3. Mean (± SE) leaf damage on bean plant treated with leaf extracts of Tephrosia vogelii.

TreatmentWBS1WAS2WAS3WAS4WASCM%ROC
T12.2 ± 0.42ab1.8 ± 0.10ab1.8 ± 0.10ab1.7 ± 0.15abc1.7 ± 0.19ab1.7521.5
T21.80 ± 0.25a1.67 ± 0.07ab1.47 ± 0.15ab1.5 ± 0.17abc1.4 ± 0.17ab1.5132.2
T31.47 ± 0.23a1.37 ± 0.13ab1.22 ± 0.15a1.37 ± 0.18abc0.7 ± 0.37a1.1648
T41.5 ± 0.26a1.2 ± 0.12a1.07 ± 0.07a1.3 ± 0.15abc1.1 ± 0.10a1.1747.5
T52.0 ± 0.21a2.0 ± 0.00ab2.0 ± 0.00ab1.9 ± 0.10bc1.6 ± 0.23ab1.8816
T61.47 ± 0.03a1.4 ± 0.21ab1.3 ± 0.19a1.7 ± 0.25abc1.3 ± 0.28ab1.4336
T71.37 ± 0.12a1.43 ± 0.28a1.33 ± 0.2a1.4 ± 0.18abc1.27 ± 0.27ab1.3639
T81.4 ± 0.25a1.4 ± 0.23ab1.27 ± 0.15a1.27 ± 0.1ab1.63 ± 0.17ab1.3937.6
T91.13 ± 0.09a1.27 ± 0.27a1.3 ± 0.33a1.0 ± 0.00a1.0 ± 0.00a1.1548.4
T10Grand meanP value2.3 ± 0.33b1.70.0342.3 ± 0.33ab1.590.182.3 ± 0.33b1.50.0032.03 ± 0.09c1.520.0032.03 ± 0.09c1.40.0082.23–

Values are expressed as Mean ± SEM of three replicates. Values with the same alphabet within the same row are not significantly different. CM, Cumulative mean, WBS, Week before spray, WAS, Week after spray, %ROC, Percentage reduction over control.

T1=2% TVE; T2 = 4%TVE; T3 = 8%TVE; T4 = 10% TVE; T5 = 2.2 TVE%; T6 = 4.2 TVE%; T7 = 8.2%TVE, T8 = 10.2%TVE, T9=Synthetic pesticides, T10=Water only. TVE, Tephrosia vogelii extracts.

3.5 Effect of Tephrosia vogelii leaf extracts on yield and yield parameters

Table 4 shows that the treatments had a significant effect on yield (p=0.001), pod weight (g) (p =0.001), number of seeds per pod (p = 0.01), number of pods per plant (p = 0.011), and 100 seed weight (g) (p=0.001). For leaf extract treatments, 10.2% gained the significantly highest 100 seed weight (2.9 ± 0.08), number of pod per plant (8.67 ± 0.7) and weight of pod (3.06 ± 0.04),all of which were significantly greater than the rest of treatments (p≤ 0.05). Furthermore, 10% extract produced showed highest number of seed per pod (6.33 ± 0.3). The untreated plot (control) showed significantly lower average yield (401.4± 5.9) compared to the treated plot with Tephrosia vogelii leaf extracts. Among the botanical treatments, the 10.2%, T.vogelii leaf extract showed significantly higher bean yields than other extract concentrations (p≤ 0.05) resulted in the highest grain yield (736.3 ± 25.5) and superior yield components overall. However, synthetic treatments grain yield did not significantly change from that obtained with the high concentration 10.2% T.vogelii leaf extract (736.3 ± 25.5).

Table 4. Mean yield and yield parameters of common beans during harvesting period.

TreatmentsWeight of pod (g)No. of seed per pod100 seed weight (g)Pod number per plantYield (kg/ha)
T11.7 ± 0.03a4.00 ± 0.6cd51.67 ± 6.1bc8.00 ± 0.6a558.3 ± 0.36a
T21.9 ± 0.03abc5.0 ± 0.6ab58.33 ± 3.7ab8.0 ± 0.0<sup>a</sup>576 ± 43.3 a
T32.3 ± 0.2c4.67 ± 0.9ab62.33 ± 1.2ab8.33 ± 0.3a663.7 ± 26.5abc
T42.8 ± 0.1d6.33 ± 0.3c62.33 ± 3.2ab8.33 ± 1.2a709.6 ± 4.81c
T51.8 ± 3.1abc4.33 ± 0.7abc44.33 ± 3.3cd6.67 ± 0.9a571.9± 121a
T62.05 ± 0.2abc5.33 ± 0.7abc62.00 ± 2.6ab7.67 ± 0.3a584.5 ± 15.2abc
T72.36 ± 0.2b5.00 ± 0.6abc65.00 ± 1.0a6.67 ± 2.3a677.4 ± 22.9abc
T82.9 ± 0.08d5.00 ± 0.6abc64.67 ± 1.5ab8.67 ± 0.7a736 ± 25.5b
T93.06 ± 0.04d5.67 ± 0.3bc67.00 ± 1.0a9.33 ± 0.3a763 ± 20.5bc
T10Grand meanP value1.5 ± 3.07a2.250.0012.6 ± 7.7d4.90.0140.00 ± 6.8d400.0012.67 ± 1.2c7.430.011401.4± 5.9d624.30.001

Values are expressed as Mean ± SEM of three replicates. Values with the same alphabet within the same row are not significantly different. T1=2%TVE; T2 = 4%TVE; T3 = 8%TVE; T4 = 10% TVE; T5 = 2.2%TVE; T6 = 4.2%TVE; T7 = 8.2%TVE; T8 = 10.2%TVE, T9=Synthetic pesticides, T10=Water only. TVE, Tephrosia vogelii extracts.

3.6 Correlation between leaf damage and aphid population

The aphid population and leaf damage exhibited a positive linear relationship as shown in Figure 7. The trend line equation was y = 41.666x+42.006, and the coefficient of determination (R²) was 0.6954. The regression analysis of mean aphid population and total leaf damage indicated that the total bean yield accounted for 69.5% of the variation on bean leaf damage.

3.7 Correlation between leaf damage and total yield

There was a negative linear relationship between total yield in kg/ha and total leaf damage with an adequate portrayal of the data was provided by the well-fitted regression equation (y = -272.98x + 1034.5) displayed graphically in Figure 8. The fitted regression line had a substantial regression coefficient, as further evidenced by the coefficient of determination (R2 = 0.804). The regression analysis of total bean yield and total leaf damage revealed that total bean yield accounted for 80% of the variation in total leaf damage.

4 Discussion

The Tephrosia vogelii plants collected from Morogoro were identified as chemotype 1 based on both morphological and phytochemical +characteristics. The presence of white flowers, a morphological trait commonly associated with chemotype 1, was confirmed in the collected plants, and subsequent LC-MS analysis verified the presence of rotenone, the principle bioactive rotenoid characteristic of this chemotype (Mkindi et al., 2019).These findings agreeable with those of Mkindi et al. (2019), that found a strong correlation between white flower and presence of particular chemotype in T.vogelii.

This current study also evaluated the presence and identity of biologically active compounds of leaf extracts of T.vogelii using LC-MS analysis (Figure 6). This study revealed the presence of 6 compounds such as Rotenone, Quercetin, Isoquercitin, 6,4-Dimethoxy-7-hydroxyiflavone, and glycetein which are in T.vogelii. Compounds found in this study were the same phytochemicals that were reported in T.vogelii leaves in previous studies (Nana et al., 2024; Stevenson et al., 2012; Belmain et al., 2012; Mlozi et al., 2022).

Chemical structures of identified compounds of *Tephrosia vogelii* leaf extracts.
Figure 6. Chemical structures of identified compounds of Tephrosia vogelii leaf extracts.
Regression relationship between leaf damage and aphid population.
Figure 7. Regression relationship between leaf damage and aphid population.
Regression relationship between total leaf damage and bean total yield.
Figure 8. Regression relationship between total leaf damage and bean total yield.

This study demonstrated that T.vogelii leaf extracts effectively suppressed A.fabae populations and reduced aphid-induced leaf damage than the untreated control. The highest reduction in aphid population and leaf damage was observed in treatments with high concentration of T.vogelii leaf extracts. This might be attributable to the various insecticidal action compound found in T.vogelii leaf extracts such as quercetin and rotenone. The efficacy is likely attributable to the higher concentrations of bioactive compounds, particularly rotenone, deguelin, tephrosin and flavonoids such as quercetin, which have previously been recorded to possess insecticidal activity against wide range of insect pests such as aphids (Tembo et al., 2018; Makila et al., 2018). In this study, the effectiveness of synthetic pesticides as a positive control appeared to outperform that of botanical pesticides. Mpumi et al. (2016) reported that synthetic pesticides are expected to exhibit less selectivity and pose a significant effect to agricultural pests. Once more, the prolonged residual effects of synthetic pesticides in the environment render them hazardous not only to humans and consumers but also to a variety of other creatures (Isman and Grieneisen, 2014). In every treatment, bean aphids started to accumulate one week before spraying. However, the Tephrosia vogelii leaf extracts were efficient in lowering the population of aphids throughout the sampling time. It’s possible that the early penetration of these T.vogelii leaf extracts contributed to the treatments’ effectiveness against aphis fabae. This is supported by the findings of Kayange et al. (2019) who reported the decrease in the population of Aphis fabae following spraying suggests that T.vogelii leaf extracts had effective pesticidal activities against aphids.

The aphid population dropped progressively following application of the treatments, which might be attributed to a number of variables such as T.vogelii leaf extract repellant properties and plant senescence. Throughout the sampling period, the control treatment showed the highest aphid population compared to the other treatments. According to Makila et al. (2018), aphid populations will grow exponentially if left unchecked and will only be constrained by the availability of food sources and other selection forces. Aphids can proliferate quickly due to their quick development (8–12 days) from first instars nymph to adult, ability to reproduce even in the absence of males, and long reproductive life span (Mudzingwa et al., 2013). Although it was not concluded that the decrease in aphid population and leaf damage was a result of repellent activities from T.vogelii leaf extracts, but T.vogelii leaf extracts used in this study possess repellent activities. During the experimental period, high rainfall and cooler weather conditions may have reduced aphid development and reproduction. Previous studies have shown that heavy rainfall can physically remove aphid from host plants and reduce their population growth, while cool temperatures generally slow aphid reproduction (Tomar, 2010; Wosula, 2016). Thereby, the observed suppress in aphid populations was probably related to the combined result of treatment effects and prevailing environmental condition. There was also significance difference of bean leaf damage in all T.vogelii leaf extracts (p > 0.05) except for 1 week after spray. This is supported by the findings of Murovhi et al. (2020) who reported the decrease in the leaf damage following spraying suggests that pesticidal leaf extracts had effective pesticidal activities against pests hence reduce leaf damage. The reduction in leaf damage and aphid population density within treatments clearly demonstrates that the T.vogelii leaf extracts were efficient in lowering the number of aphids.

When compared to control treatments, all T.vogelii leaf extracts and synthetic pesticides treatments produced higher common bean yields. This result is in support of Mkindi et al. (2020) who discovered that applying T.vogelii leaf extracts to the field crops increases yield production per plant. Bean aphid infestation significantly affected all measured yield components, including pod weight, number of pods per plant, number of seeds per pod,100-seed weight and grain yield. The control plot, which maintained the highest aphid population and greatest leaf damage, produced the lowest values for all yield components (Mlozi et al., 2020). These results were in line with those of Mwangi et al. (2008) and Singh et al. (2017) who noted a significant decline in bean grain yield on common bean varieties that were susceptible to bean aphid infestation. According to Minja et al. (2001) plant growth is stunted and leaves turn yellow and curl as a result of aphid infestation and leaf damage. This reduces the leaf area index and consequently the total quantities of carbohydrates that contribute to total plant biomass, resulting in lower common bean yield (Mudzingwa et al., 2013). Tephrosia vogelii leaf extract treatments were successful in lowering aphid population and bean leaf damage, hence assisting in bean production improvement.

Although T.vogelii is recognized as a nitrogen-fixing shrub that produces nitrogen rich biomass (Mafongoya et al., 2003; Munthali et al., 2014; Tembo et al., 2018; Kayange et al., 2019), the present study evaluated foliar leaf extracts as botanical pesticides rather than soil amendments. Therefore, the yield improvement observed in this study is more appropriately attributed to reduced aphid damage than to any fertilizer effect. This study found that synthetic pesticide and T.vogelii leaf extract treatments significantly changed the yield of common beans. The regression analysis further supported the relationship between aphid infestation, leaf damage, and crop productivity. Aphid population density was positively associated with leaf damage, indicating that increasing aphid infestations resulted in greater damage to foliage. Likewise, grain yield showed a strong negative relationship with leaf damage, demonstrating that yield declined as leaf damage increased. The relationship confirmed that effective suppression of Aphid fabae reduced leaf injury and contributed to improved grain yield.

The common bean yield in kg/ha made this very evident, as the leaf damage increases caused the yield of the control treatments to be quite low. This correlation result is consistent with the findings of Murovhi et al. (2020) who reported that leaf damage caused by aphids typically results in lower yields, which have an adverse effect on market value and may even cause crop failure. The regression analysis results of total common bean yield and total leaf damage revealed that total bean yield accounted for 80.4% of the variation in leaf damage. The current findings showed a negative relationship between the total yields, total aphid population and total leaf damage, indicating that higher common bean yields were strongly influenced by lower total aphid population and total leaf damage. These results suggest that feasting directly on common bean leaves by A.fabae may reduce the plant’s ability to perform several tasks. This was supported by Goławska et al. (2023) who discovered a substantial decrease in photosynthetic rate on aphid-damaged leaves. Also, this result aligns with the results reported by Heng-Moss et al. (2003) which showed that aphid leaf damage resulted in a significant drop in the photosynthetic rate. This correlation study demonstrates that pesticidal plants such as T.vogelii may efficiently used as a foliar fertilizer to improve crop production and aphid’s management tool.

5 Conclusion and recommendation

Tephrosia vogelii chemotype 1 leaf extracts effectively suppressed bean aphids, reduced leaf damage, and improved common bean yield. The performance of the 10.2% extract was compared to that of synthetic pesticide, indicating that T.vogelii has considerable potential as an affordable and environmentally sustainable botanical pesticide for aphid management in common bean production. These T.vogelii leaf extracts, which can easily be exploited by smallholder farmers as the foundation for effective development and marketing of botanical pesticides in less developed countries like Tanzania where agriculture is the primary source of revenue. It is advised that more research to be done so as to investigate the indicators for chemotype 1 and to evaluate the long-term ecological effects of T.vogelii leaf extracts. Further works may involving multiple locations and seasons, formulation development, phytotoxicity, non target effects, persistence, economic assessment and optimization of application rates. Lastly, in view of the aforementioned concerns of inorganic pesticides, these T.vogelii leaf extracts are recommended to be incorporated in future integrated management of bean aphids in large scale agriculture as biorational pest control tools.

Correction note

This article has been corrected with minor changes. These changes do not impact the scientific content of the article.

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Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fagro.2026.1900866/full#supplementary-material

Supplementary material Supplementary material at the source

Footnotes

Edited by: Shijun You, Fujian Agriculture and Forestry University, China

Reviewed by: Hend Omar Mohamed, Agricultural Research Center, Egypt

Nikhil Hatwar, Banaras Hindu University, India

Statements

Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Funding

The author(s) declared that financial support was not received for this work and/or its publication.

Data availability

The original contributions presented in the study are included in the article/Supplementary Material. Further inquiries can be directed to the corresponding author.

Author contributions

DN: Visualization, Data curation, Software, Writing – original draft, Formal analysis, Project administration, Methodology, Resources, Conceptualization, Writing – review & editing, Funding acquisition, Validation, Investigation. RM: Supervision, Writing – review & editing. PL: Supervision, Writing – review & editing.

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Citation

Nana, D. S., et al. (2026). Field efficacy of Tephrosia vogelii leaf extracts against Aphis fabae Scopoli (Hemiptera: aphididae) on common bean (Phaseolus vulgaris). Frontiers in Agronomy, Volume 8. https://doi.org/
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Copyright © 2026 Nana, Lyimo and Majubwa.

License: https://creativecommons.org/licenses/by/4.0/

*Correspondence: Dominick Stephen Nana

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