Evaluation of botanicals and biopesticides against diamondback moth, Plutella xylostella (L.) infesting cabbage under western Uttar Pradesh conditions

Introduction

Cabbage (Brassica oleracea L. var. capitata) is one of the most widely cultivated and economically important vegetable crops worldwide. It is an important leafy vegetable grown extensively in Africa, including Ethiopia, where it serves as both a staple food and a valuable source of income for farmers. Despite its importance, cabbage productivity in Ethiopia, particularly in the Amhara Regional State, remains considerably lower than the global average. Ethiopia produces approximately 6 t ha⁻¹ of cabbage, compared with an average yield of 16 t ha⁻¹ in East Africa and 28.8 t ha⁻¹ worldwide (CSA, 2021; Habtamu & Mnuyelet, 2022) [1,2] . Several biotic and abiotic factors limit cabbage production, among which aphids are one of the most destructive insect pests. In addition to causing direct damage through sap feeding, aphids transmit nearly 50% of insect-borne plant viruses, resulting in substantial reductions in crop yield, quality and nutritional value (Gebreyohans, 2021; Opfer & McGrath, 2013) [3,4] . Severe aphid infestations have been reported to cause yield losses ranging from 36.1% to 91.2% and in extreme cases, complete crop failure (Lidet et al., 2008) [5] . In the Amhara Region of Ethiopia, cabbage aphids are considered a major production constraint, with reported yield reductions of 50-80% (Kassahun, 2018; Abdelmuhsin et al., 2022; Fiodorova et al., 2022; Zakinyan et al., 2023; Negreiros et al., 2024) [6][7][8][9][10] . Although synthetic insecticides remain the primary method for managing cabbage aphids and improving crop productivity (Iqbal et al., 2011) [11] , their indiscriminate use has resulted in insecticide resistance, pesticide residues, adverse effects on beneficial organisms and human health, environmental contamination and increased production costs (Shiberu & Mulugeta, 2016) [12] . Consequently, environmentally safe alternatives have gained increasing attention. Botanical pesticides, derived from plant materials, possess insecticidal and repellent properties while posing minimal risk to non-target organisms and the environment (Zahid et al., 2016; Mahmood et al., 2022) [13,14] . Therefore, the present

Experimental crop and design

The cabbage variety 'Golden Acre' was transplanted following the recommended agronomic practices. The experiment was laid out in a Randomized Block Design (RBD) with seven treatments, including an untreated control and three replications. Each experimental plot measured 3.0 × 4.0 m, maintaining a spacing of 60 × 50 cm between rows and plants.

Treatments and application

The treatments comprised Spinosad 45 SC (160 ml ha⁻¹), Agniastra (10 L ha⁻¹), Bacillus thuringiensis var. kurstaki (2 kg ha⁻¹), Metarhizium anisopliae (2 kg ha⁻¹), NSKE 5% (1.5 kg ha⁻¹), Nimbecidine 0.03% (2 L ha⁻¹) and an untreated control. Two foliar sprays were applied at a 15-day interval after the pest population reached the Economic Threshold Level (ETL) of 2 larvae per five plants using a knapsack sprayer.

Recording of observations

Observations on diamondback moth (P. xylostella) larval population were recorded from five randomly selected plants in each plot. Pre-treatment observations were recorded one day before spraying, while post-treatment observations were taken on the 3 rd , 7 th and 14 th day after each spray. The efficacy of treatments was assessed based on the mean larval population per plant.

Statistical analysis

The experimental data were subjected to Analysis of Variance (ANOVA) after square-root transformation [√(𝑥 + 0.5)] of larval count data. Treatment means were compared at the 5% level of significance and the Incremental Cost-Benefit Ratio (ICBR) was calculated to assess the economic viability of different treatments.

Result

The (2025) [21] , Sharma et al. (2024) [22] , Prakashrao and Kumar (2022) [23] Kommoji et al. (2022) [24] , Kumar et al. (2022) [20] , who also reported efficacy of different insecticide and biopesticide in cabbage ecosystems under different agroclimatic regions of India.

Discussion

The present study revealed that all the evaluated botanicals and biopesticides significantly reduced the larval population of the diamondback moth (Plutella xylostella) compared with the untreated control. Among the treatments, Spinosad 45 SC was the most effective, followed by Bacillus thuringiensis var. kurstaki and Metarhizium anisopliae, whereas Nimbecidine 0.03% and NSKE 5% showed moderate efficacy and Agniastra was comparatively less effective.The superior performance of Spinosad observed in the present investigation is in close agreement with the findings of Ranjbari et al. (2011) [25] , Stanikzi et al. (2016) [26] , Dotasara et al. (2017) [27] , Gaddam et al. (2021) [28] , Prakashrao and Kumar (2022) [23] , Sharma et al. (2022) [29] and Choudhary et al. (2025) [21] , who also reported Spinosad as one of the most effective treatments against P. xylostella. Similarly, the effectiveness of Bacillus thuringiensis corroborates the reports of Vanlaldiki et al. (2013) [30] , Singh et al. (2015) [31] , Kumar et al. (2022) [20] and Sharma et al. (2024) [22] , while the moderate efficacy of Metarhizium anisopliae agrees with the findings of Shehzad et al. (2021) [18] and Sapkota et al. (2022) [17] . The moderate performance of neem-based treatments is also consistent with the observations of Liang et al. (2002) [15] and Sitotaw et al. (2009) [16] .

Conclusion

The present study demonstrated that all the tested botanicals and biopesticides significantly reduced the larval population of the diamondback moth, Plutella xylostella, compared with the untreated control. Among the evaluated treatments, Spinosad 45 SC proved to be the most effective, recording the lowest larval population and the highest reduction over control after both sprays. Bacillus thuringiensis var. kurstaki and Metarhizium anisopliae were the next most effective treatments, whereas neem-based products and Agniastra provided moderate suppression of the pest. The findings indicate that Spinosad 45 SC, followed by Bacillus thuringiensis var. kurstaki, can be effectively incorporated into integrated pest management (IPM) programmes for sustainable and eco-friendly management of diamondback moth in cabbage under the agro-climatic conditions of Western Uttar Pradesh.

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