Efficacy of diatomaceous earth, and entomopathogenic fungi, Beauveria bassiana, and Trichoderma asperellum in combination and separately, against Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae)

Ozdemir Egyptian Journal of Biological Pest Control (2023) 33:48 https://doi.org/10.1186/s41938-023-00699-8 Egyptian Journal of Biological Pest Control Open Access RESEARCH Efficacy of diatomaceous earth, and entomopathogenic fungi, Beauveria bassiana, and Trichoderma asperellum in combination and separately, against Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) Ismail Oguz Ozdemir1*    Abstract Background Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) is one of the most significant pests infesting leguminous crops since it is found in tropical and subtropical climates, as well as in Turkey. The most often utilized methods of managing these insects are fumigants and synthetic insecticides. However, chemical pesticides lead to increased risks for human health, chemical residues, insect resistance, and environmental contamination. Therefore, the present study aimed to determine the effectiveness of entomopathogenic fungi [Beauveria bassiana (Bb) and Trichoderma asperellum (Ta)] individually or in combination with diatomaceous earth (DE) against C. maculatus. The fungi Bb and Ta were applied at 1 × 104, 1 × 106 and 1 × 108 spores/kg of chickpea seeds and mixed with 200, 400, 800 mg/kg of DE. Additionally, the progeny production of the insect on chickpea in the different treatments was evaluated after 40 days of exposure. Results In all individual treatments, total adult mortality of the insect was accomplished solely by using the highest DE treatment rate (800 mg/kg) after 7 days. The most effective combination that was a mixture at highest application rate of DE/Bb (800 mg/kg of DE + 1 × 108 spores/kg of Bb) caused 100% mortality after 6 days of exposure and had the lowest L T50 (2.97) and L T90 (5.46) values (days). Although other DE/Bb binary combinations caused 100% mortality of C. maculatus 6 days after treatment, their LT50 and LT90 values were lower. Insect mortalities were 100% in all DE/ Ta binary combinations on days 7 and 8, and the highest application rate (800 mg/kg of DE + 1 × 108 spores/kg of Ta) of this combination had the lowest LT50 (4.14) and L T90 (6.17) values (days). Individual treatments of DE, Bb, Ta and their binary combinations caused significant reduction in progeny production after 40 days of treatment compared with progeny production in the control of C. maculatus. The highest progeny production (88.9%) was observed at the highest treatment rate of DE/Bb combinations (800 mg/kg of DE + 1 × 108 spores/kg of BB). Conclusions The treatments used in combination of Bb or Ta with DE resulted in increased insecticidal effectiveness against C. maculatus. These natural agents caused considerable decreasing of progeny production of the pest. Even *Correspondence: Ismail Oguz Ozdemir Full list of author information is available at the end of the article © The Author(s) 2023. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. Ozdemir E gyptian Journal of Biological Pest Control (2023) 33:48 Page 2 of 8 with reduced application rates, the agents with a promising potential against the pest showed acceptable results in binary combinations. Keywords Callosobruchus maculatus, Legumes, Chickpea, Storage pest, Biocontrol, Progeny production Background Legumes have a significant role in human nutrition due to their high protein, lipid, and carbohydrate content, as well as in soil fertility. Some seed beetles cause significant damage in the places where these legumes are cultivated and stored. The Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) is one of the most significant pests infesting leguminous crops since it is found in tropical and subtropical climates all over the world, as well as many areas of Turkey (Gad et al. 2021). This pest attacks legume in the field and in storage, causing physical damage and quality loss through post-harvest feeding and reproductive activities. Furthermore, it causes significant economic losses in stored legume seeds due to decreased weight and germination (Musa and Adeboye 2017). The most often utilized methods of managing these pest are fumigants and synthetic insecticides (Wolfson et al. 1991). However, chemical pesticides lead to increased risks for human health, chemical residues, insect resistance, and environmental contamination (Rizwan et al. 2019). For these reasons, the application of sustainable alternative management tools such as eco-friendly botanical insecticides, physical treatments, inert dusts, and microbial/biocontrol agents has been assessed (Abdelgaleil et al. 2021). The diatomaceous earth (DE) as an inert dust is a wellstudied fossil alternative that occurs naturally and commonly used as a preservative in grains and is safe for natural enemies and mammals (Kalleieratos et al. 2012). This DE has a variety of formulations across the world and used efficiently against many stored product pests (Wakil et al. 2010) by scratching the cuticle of the insects and causing dehydration of its body (Korunic 1998). However, the material, which is effective at high application ratio (1000–3500 mg/kg) (Permual and Le Patourel 1992), has detrimental impacts in the applied products, such as seed bulk density, seed flowability, and visible residues (Golob 1997). For this reason, it is suggested that the dose should be reduced and used in combination with other seed protectants (Ziaee et al. 2021). Several studies have been conducted to assess the efficacy of the binary combination of DE with several entomopathogenic fungi (EPFs), such as Beauveria bassiana (Balsamo) (Hypocreales: Clavicipitaceae) (Rizwan et al. 2019) and Trichoderma harzianum Rifai (Hypocreales: Hypocreaceae) (Abdelgaleil et al. 2021). Combinations of natural agents with different modes of action, such as DE and EPF, can provide an effective approach to control of storage pests by decreasing toxic residues in products, lowering application doses, and boosting the efficacy of these agents (Gad et al. 2021). Entomopathogenic fungi are promising alternative agents with their high virulence against stored product insect-pests that can be applied instead of chemicals. They get attention owing to the fact that it does not have any (...truncated)