Effect of Entomopathogens on Angoumois Grain Moth and Seed Viability
Abstract
The laboratory experiment on the effect of entomopathogens on the Angoumois grain moth, Sitotroga cerealella Olivier revealed that the significantly highest percent adult mortality (72.33%) of S. cerealella was recorded in deltamethrin at 0.04 mL/kg after 72 hours of treatment. In case of entomopathogens, the treatment of M. anisopliae 1.15 WP (1.0 × 108 CFU/g) + diatomaceous earth @ 20 + 5 g/kg was found to be the next effective treatment having 65.80% adult mortality. The significantly lowest percent adult mortality (38.33%) of S. cerealella was recorded in Metarhizium anisopliae 1.15 WP (1.0 × 10⁸ CFU/g) at 10 g/kg after 72 hours of treatment. In case of adult emergence, the significantly lowest adult emergence (2.00) was recorded in deltamethrin at 0.04 mL/kg. The significantly highest seed germination (91.33%) was recorded in treatment of B. bassiana 1.15 WP (1.0 × 10⁸ CFU/g) + diatomaceous earth at 20 + 5 g/kg and M. anisopliae 1.15 WP (1.0 × 10⁸ CFU/g) + diatomaceous earth at 20 + 5 g/kg (91.00%). The significantly lowest seed moisture content (8.24%) was recorded in B. bassiana 1.15 WP (1.0 × 10⁸ CFU/g) + diatomaceous earth at 20 + 5 g/kg and it was statistically at par with M. anisopliae 1.15 WP (1.0 × 10⁸ CFU/g) + diatomaceous earth at 20 + 5 g/kg (8.41%).
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Introduction
Sorghum is a significant cereal crop that is widely cultivated in tropical and subtropical climates worldwide. It is essential for industrial applications, fodder and food security. Among all the biotic factors, insect pests are considered the most important and cause huge losses in the cereal grains (30%–40%) (Kumar, 2017). The Angoumois grain moth is a serious primary pest of stored grain in many parts of the world especially on stored wheat and rice (Boshra, 2007). The control of stored-grain insect pests using chemical insecticides and fumigants (methyl bromide and phosphine) is an essential tool for preventing or minimizing insect damage to stored grain. However, the use of synthetic insecticides in stored grain protection resulted in potential hazards for mammals (Mostafalou and Abdollahi, 2013), can be harmful to the natural enemies and insects develop resistance to them (Prakash et al., 1993; Salem et al., 2007). These problems had necessitated the development of new classes of safer insect control agents that would be biodegradable, cheap, readily available and non-toxic to consumers and environmentally friendly. Biological control of stored-product insect pests involves the use of hymenopteran parasitoids, predatory insects and mites as well as insect pathogens such as entomopathogenic fungi, bacteria, viruses, protozoa and nematodes (Moore et al., 2000; Flinn and Scholler, 2012). Among insect pathogens, entomopathogenic fungi represent a promising alternative to chemical insecticides and conventional pesticides. The conidia of these fungi attach to the insect cuticle, germinate and penetrate the integument, ultimately leading to the death of the host. Entomopathogenic fungi are naturally occurring, environmentally safe and exhibit low toxicity to mammals (Cox and Wilking, 1996). The use of diatomaceous earth offers another promising alternative to conventional insecticides. Its particles abrade and inactivate the epicuticular lipids of the insect cuticle leading to internal water loss and eventually death by desiccation (Ebeling, 1971; Korunic, 1998; Mewis and Ulrichs, 2001).
Conclusion
The study demonstrated that entomopathogenic fungi, particularly in combination with diatomaceous earth, are effective alternatives to chemical insecticides for managing Sitotroga cerealella in stored sorghum. The combination treatments of M. anisopliae + diatomaceous earth and B. bassiana + diatomaceous earth at 20 + 5 g/kg showed significantly higher adult mortality, reduced adult emergence, lower oviposition, minimized weight loss, and maintained better seed viability compared to individual treatments.
Key Findings:
- The combination of M. anisopliae (1.0 × 10⁸ CFU/g) + diatomaceous earth at 20 + 5 g/kg was the most effective entomopathogenic treatment, achieving 65.80% adult mortality, 91.00% seed germination, and only 8.41% seed moisture content.
- B. bassiana (1.0 × 10⁸ CFU/g) + diatomaceous earth at 20 + 5 g/kg was the second most effective treatment, with comparable results.
- Chemical insecticide (deltamethrin) showed the highest adult mortality (72.33%) but also maintained good seed viability (90.00% germination), indicating its effectiveness as a grain protectant.
- Deltamethrin is effective but raises concerns about residues, resistance development, and environmental impact. Therefore, entomopathogens combined with diatomaceous earth offer a sustainable alternative for stored grain pest management.
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