Compatibility and Laboratory Bioefficacy of Beauveria bassiana Isolates Combined with Selected Insecticides against Plutella xylostella L.

Assessment of Insecticidal Compatibility of Metarhizium anisopliae Isolates against Diamondback Moth (Plutella xylostella L.)

The diamondback moth, Plutella xylostella (L.), is a serious insect pest of cruciferous crops and has developed widespread resistance to several insecticides, necessitating the development of alternative management strategies. The present investigation was undertaken to determine the compatibility of different Metarhizium anisopliae isolates with selected insecticides and to evaluate their efficacy against P. xylostella. The experiment was conducted under laboratory conditions using a two-factor completely randomised design (CRD) at the Biocontrol Research and Production Centre (BRPC), Department of Entomology, College of Agriculture, Jawaharlal Nehru Krishi Vishwa Vidyalaya (JNKVV), Jabalpur, Madhya Pradesh, during 2024–2025. Five isolates of M. anisopliae were tested in combination with spinosad, indoxacarb, fipronil and emamectin benzoate. Compatibility was assessed on the basis of radial mycelial growth, percentage inhibition, spore production and spore viability, while insecticidal activity was determined against third-instar larvae of P. xylostella. Significant variation was observed among the fungal isolates, insecticides and their interactions. ITCC-6895 exhibited the greatest radial growth (78.96 mm at 7 DAI), whereas NBAII Ma-6 showed the lowest. Emamectin benzoate exhibited the greatest compatibility with the fungal isolates and produced synergistic interactions with NBAIR Ma-56b and Ma LOCAL. Ma LOCAL recorded the highest spore viability (97.10%), while both Ma LOCAL and NBAII Ma-6 produced the highest mean spore count (1.54 × 10⁸ spores mL⁻¹). In the laboratory bioassays, all insecticides resulted in complete larval mortality after 120 h, whereas ITCC-6895 recorded the highest average mortality (94.83%) among the fungal isolates. NBAIR Ma-56b and Ma LOCAL showed highly compatible interactions with emamectin benzoate, as indicated by negative percentage inhibition values. These findings indicate that compatible combinations of M. anisopliae, particularly ITCC-6895 and Ma LOCAL, with emamectin benzoate can improve the management of P. xylostella as part of an integrated pest management programme. Overall, compatible combinations of M. anisopliae with selective insecticides demonstrated strong potential for the environmentally sound management of P. xylostella.

Potential biocontrol efficacy of native Beauveria bassiana against diamondback moth (Plutella xylostella) and aphid (Brevicoryne brassicae) in cabbage

Comparative Evaluation of Biopesticides for the Management of Leucinodes orbonalis Infesting Brinjal

Brinjal shoot and fruit borer, Leucinodes orbonalis, is a major pest of brinjal that causes serious damage to shoots and fruits. This field study evaluated the relative efficacy of selected biopesticides and biorational insecticides against L. orbonalis during the Kharif season of 2023 at the College of Agriculture, Hassan. The experiment was laid out in a randomised block design with eight treatments and three replications. The treatments comprised Metarhizium rileyi, Beauveria bassiana, azadirachtin 1,500 ppm, Metarhizium anisopliae, azadirachtin 10,000 ppm, spinosad 45% SC, chlorantraniliprole 18.5% SC as the standard check, and an untreated control. Two sprays were applied: the first at the initiation of infestation and the second 15 days later. Shoot infestation was recorded 3, 7, and 14 days after each spray, whereas fruit infestation was recorded at harvest. Chlorantraniliprole recorded the lowest pooled shoot infestation (2.78%) and fruit infestation (17.26%). Among the tested biopesticide and biorational treatments, spinosad recorded the lowest pooled shoot infestation (3.72%) and fruit infestation (19.06%), followed by azadirachtin 10,000 ppm. Entomopathogenic fungi were less effective than spinosad and azadirachtin but performed better than the untreated control. The findings indicate that spinosad and azadirachtin may be useful components of an integrated management programme for L. orbonalis.

Bioefficacy of Indian Beauveria bassiana and Lecanicillium lecanii isolates against Lipaphis erysimi (Hemiptera: Aphididae) and their safety to Apis cerana (Hymenoptera: Apidae)

Environmental issues associated with the excessive use of chemical substances have received increasing attention globally, particularly regarding their effects on non-target/beneficial insects such as pollinators. To overcome such drawbacks, alternative control methods are being increasingly evaluated. A study was conducted to assess the effectiveness of two Indian biopesticidal isolates against the mustard aphid, Lipaphis erysimi, on rapeseed crops and to investigate their potential risks to the pollinator honeybee, Apis cerana. Laboratory bioassays showed that Beauveria bassiana AS-4220 was the most effective material against L. erysimi after 24 h (LC50 = 95.5 ppm); however, neem seed oil was the most toxic to A. cerana after the same time interval (LC50 = 185.4 ppm). The highest reduction in the aphid population under field conditions was observed with B. bassiana AS-4220 at 3 × 108 spores mL− 1 ten days after field treatment (71.9%), followed by B. bassiana AS-4220 at 2 × 108 spores mL−1 ten days after field treatment (70.7%). The highest PT (persistent toxicity index) and RPT (relative persistent toxicity) values were observed for B. bassiana at 3 × 108 spores mL− 1 (799.98 and 1.06, respectively). The benefit: cost ratio among the treatments was highest for B. bassiana at 3 × 108 spores mL− 1 (4.90:1). However, the highest honeybee mortality was observed following treatment with neem seed oil at 3 mL L− 1 and B. bassiana at 3 × 108 spores mL− 1 ten days of treatment (100%). No significant inhibition of acetylcholinesterase (AChE) activity was observed in honeybees 24 h after treatment. The study demonstrates that entomopathogenic fungi effectively control L. erysimi while posing some risk to A. cerana, particularly at higher concentrations, necessitating careful timing of application . Therefore, these treatments may be used to manage L. erysimi in rapeseed crops while minimizing effects on A. cerana bees, provided that application is scheduled during periods of low foraging activity.

Bioactivity screening of plant ethanol extracts against Plutella xylostella and field evaluation of an optimized botanical combination formulation

Plutella xylostella is a major pest of cruciferous vegetables. The prolonged overuse of chemical insecticides has resulted in increased resistance in P. xylostella populations, highlighting the urgent need for environmentally friendly and effective alternative control strategies. In this study, ethanol extracts from 15 plant species collected from the Qinling Mountains of China were systematically evaluated for their insecticidal, antifeedant, and oviposition-repellent activities against P. xylostella. Laboratory bioassays were conducted using leaf-dipping and leaf-disc methods. Among the tested plants, ethanol extracts of Atropa belladonna and Blumea riparia var. megacephala exhibited the strongest biological activities. Specifically, A. belladonna extract achieved corrected mortality, antifeedant, and oviposition-repellent rates of 83.11%, 89.46%, and 78.57%, respectively, whereas B. riparia var. megacephala extract produced corrected mortality, antifeedant, and oviposition-repellent rates of 73.53%, 87.45%, and 82.14%, respectively. When combined at a volume ratio of 8:2, the two extracts showed enhanced insecticidal activity, with a median lethal concentration (LC50) of 65.762 mg/mL and a co-toxicity coefficient consistent with an additive effect without antagonism. A stable emulsifiable concentrate (EC) formulation was subsequently developed through optimization of the solvent and surfactant system. Field trials demonstrated that the 10% botanical EC effectively suppressed P. xylostella populations, achieving a control efficacy of 58.35% at 7 days post-application, which was comparable to that of the commonly used insecticide emamectin benzoate. Collectively, these findings suggest that A. belladonna and B. riparia var. megacephala have potential as botanical insecticide resources for the integrated management of P. xylostella and may contribute to more sustainable agricultural practices.

Efficacy of oil infused rice-based formulations of Beauveria bassiana (Balsamo) Vuillemi isolates (BPA/B7 and BKN-20) against Helopeltis theivora Waterhouse infesting tea

The Beauveria bassiana, a soil-borne, filamentous fungus known for its entomopathogenic nature, and commonly used as a myco-insecticide to control pests. This white muscardine fungus produces a number of cyclodepsi peptides such as beauvericin which is considered for its insect toxicity. The insecticidal effectiveness of two native isolates of Beauveria bassiana (BPA/B7 and BKN-20) from tea ecosystem was evaluated against Helopeltis theivora, a major pest of tea plantations, and studied the potential of oil infused rice media to enhance fungal performance. These indigenous isolates were cultured on rice-based substrates supplemented with different organic oils, and the parameters like fungal growth, sporulation, spore viability, and pathogenicity were assessed under laboratory conditions besides its effect on tea mosquito bugs at varying concentrations. Results showed that, coconut oil-infused rice media produced the highest mycelia growth (3.78cm) and spore germination (86.1%). The isolate BPA/B7 grown on 1% coconut oil infused rice media caused over 80% mortality of H. theivora, outperforming commercial formulations. The findings indicated that, rice powder supplemented with 1% coconut oil is a cost effective and efficient substrate for large scale production of B. bassiana under laboratory condition.