Evaluating the bio-efficacy of botanical extracts and chemical insecticides against thrips in onion

Introduction

Onion (Allium cepa L.) belonging to the family Alliaceae is an important vegetable crop grown across diverse agroclimatic zones globally (Teshika et al., 2019) [14] for its culinary, nutritional, medicinal and industrial applications (Gnanasundari et al., 2023) [3] . Onion bulbs are a rich source of carbohydrates, minerals, vitamins, flavonoids and bioactive compounds which contribute to its antioxidant, antimicrobial and health-promoting properties (Ahmed et al., 2025) [1] . India is the second largest producer of onion after China, making it important domestically and for export. Despite its significance, onion yield and quality is adversely affected by several biotic and abiotic stresses among which onion thrips T. tabaci Lindeman (Thysanoptera: Thripidae), is one of the major insects due to its widespread occurrence and severe feeding damage (Jamian et al., 2024) [5] . Both nymphs and adults feed on the plant by puncturing the leaf tissues and sucking the cellular contents, causing silver discoloration, leaf curling, tip necrosis, and reduced photosynthetic activity ultimately hampering the bulb development. Severe infestations may even cause upto 90% reductions in bulb yield and quality in susceptible varieties under favourable environmental conditions (Gill et al., 2015). Moreover, T. tabaci serves as an efficient vector of several plant viruses, further increasing the damage and economic losses. The management of onion thrips majorly depends on synthetic insecticides due to their quick action and high level of effectiveness. However, continuous use of chemical insecticides has caused several health and environmental hazards including insecticide resistance and adverse effects on beneficial organisms (Pandey et al., 2023) [10] . These concerns call for environmentally sustainable alternatives that can be incorporated into integrated pest management (IPM) programmes. In this context botanical extracts have emerged as environmentally safer options due to their insecticidal, repellent, antifeedant, oviposition-deterrent and growthregulating properties and pose less risk to beneficial organisms. Plant-derived products prepared from neem, akdo, datura and other botanicals have demonstrated considerable potential against various sucking insect pests, including thrips. Therefore, this study evaluated the bioefficacy of selected botanical extracts and chemical insecticides for the management of onion thrips under field conditions.

Materials and methods

Experimental Site

The field experiment was conducted during the onion cropping season of 2025 (January to May) at the Research Farm, Faculty of Agriculture, Maharishi Markandeshwar (Deemed to be University), Mullana-Ambala, Haryana.

Procurement of seed, botanical extracts and chemicals

The seeds of onion variety Kala Patti Piyaz were procured from local market of Mullana, Ambala. For the botanical extracts the leaves of different plants were collected from the local area and then botanical extracts of neem leaf, bakane neem, datura and akdo were prepared by using cold extraction method grinding fresh plant material with distilled water, followed by filtration through muslin cloth to obtain crude extracts (Kumar et al. 2025) [7] . Moreover, the insecticides used in this study was procured from Bhatia Seeds and Pesticides store, Shahabad.

Experimental details

The experiment was laid out in a Randomized Block Design (RBD) comprising ten treatments (table 1) with three replications. Onion variety Kala Patti Piyaz was transplanted in January 2025 at a spacing of 15 × 10 cm on flat beds. All recommended agronomic practices were followed uniformly except for plant protection measures.

Application of treatments

Neem oil, castor oil and chemical insecticides were applied at the recommended concentrations using a knapsack sprayer when the thrips population reached the economic threshold level (ETL), followed by a second application after 15 days.

Observations recorded

Observations on thrips population were recorded from ten randomly selected and tagged plants in each plot at one day before treatment and at 1, 3, 7, 10, and 14 days after each spray. The efficacy of treatments was evaluated by calculating the percent reduction in thrips population using the Henderson and Tilton (1955) formula.

Data analysis

The experimental data were subjected to analysis of variance (ANOVA) using OPSTAT software, and treatment means were compared at the 5% level of significance.

Result 3.1 Bio-efficacy of different treatments against thrips in onion after first spray

The bio-efficacy of different botanical extracts and chemical insecticides against T. tabaci after the first spray revealed significant variation among the treatments (Table 2). Among all the treatments, Spinetoram 11.

Effect of different treatments on bulb yield of onion

The bulb yield of onion differed significantly among the treatments. Spinetoram 11.7 SC recorded the highest bulb yield of 16.96 kg per plot and 22,617.78 kg ha⁻¹, followed by Fipronil 80% WDG with 16.35 kg per plot and 21,804.44 kg ha⁻¹, and Cypermethrin 25% EC with 15.68 kg per plot and 20,906.67 kg ha⁻¹. Among the botanical treatments, neem oil produced the highest yield of 13.94 kg per plot and 18,591.11 kg ha⁻¹, followed by neem leaf extract with 12.67 kg per plot and 16,897.78 kg ha⁻¹. Bakane neem, datura extract, akdo extract, and castor oil recorded progressively lower yields, while the untreated control produced the lowest yield of 9.68 kg per plot and 12,911.11 kg ha⁻¹. Statistical analysis revealed significant differences among the treatments, with Spinetoram 11.7 SC being statistically at par with Fipronil 80% WDG and Cypermethrin 25% EC, whereas neem oil was the most effective botanical treatment (Table 4).

Discussion

The present study showed that Spinetoram 11.7 SC was the most effective treatment among the insecticides for reducing onion thrips population which is in corroboration with results recorded by Joseph (2014) [6] , Melissa et al. (2016) [8] and Wakil et al. (2023) [15] . The effective results could be attributed to its direct effect on nicotinic acetylcholine and GABA receptors and prolonged residual activity, which effectively controlled both nymphs and adult thrips. Spinetoram 11.7 SC was followed by Fipronil 80% WDG due to its action on GABA-gated chloride channels, which disrupt nerve impulse transmission and cause the death of the insect. Similar findings have been reported by Hosamani et al. (2012) [4] and Shitole et al. (2002) [12] . Cypermethrin 25% EC also provided effective reduction of thrips because of its stomach poison activity, which disrupts the sodium channel function in the insect nervous system. Among the botanical treatments, neem oil was the most effective followed by neem leaf extract due to the presence of azadirachtin and other limonoids, which act as antifeedant, repellent, discourage oviposition and interfere with insect growth regulation. (2025) [11] , Paidi Satyanarayana and Singh (2016) [9] and Sule (2006) [13] . Overall, the results indicate that chemical insecticides especially Spinetoram were more effective as compared to botanical extract for the effective management of onion thrips under field conditions, but these botanicals especially neem oil can be used as promising sustainable alternative in integrated pest management (IPM) programmes

Conclusion:

This study showed that both chemical insecticides and botanical extracts effectively reduced the population of Thrips tabaci and improved onion bulb yield under field conditions. Spinetoram 11.7 was the most effective treatment recording the lowest mean thrips population, maximum percent reduction after both sprays, and the highest bulb yield, among all the treatments evaluated. Fipronil 80% WDG and Cypermethrin 25% EC are also effective alternatives as they also provided effective reduction in thrips population and enhanced bulb yield. Among the botanical treatments, neem oil was the most effective, telling its potential as sustainable alternative for thrips management, followed by neem leaf extract, whereas Datura, Bakane neem, Akdo, and castor oil showed comparatively lower efficacy. The findings suggest that Spinetoram may be recommended as an effective chemical option for rapid and effective thrips control, while neem oil represents a promising eco-friendly alternative that can be integrated into sustainable integrated pest management (IPM) programmes to reduce dependency on synthetic insecticides and promote environmentally sustainable onion production.

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