Antifungal agents against Aspergillus niger for rearing rice leaffolder larvae (Lepidoptera: Pyralidae) on artificial
Abstract:
Mold contamination is an important issue in insect mass rearing. Frequently used antifungal agents such as sorbic acid and methylparaben have negative impact on many lepidopteran larvae, which might be one of the reasons for the difficulty in rearing rice leaffolder, Cnaphalocrocis medinalis (Güenée). In this study, 19 antifungal agents, including 7 food preservatives, 6 antifungal drugs, and 6 agricultural fungicides, were screened for their inhibitory activities on Aspergillus niger in diets. The results demonstrated that most of the tested chemicals are unsuitable as mold inhibitors in the diets of the rice leaffolder, and the rice leaffolder neonate is sensitive to sorbic acid and methylparaben. These two mold inhibitors at commonly used concentrations were shown to impact the survival of rice leaffolder larvae fed on artificial diets. Among the tested mold inhibitors, natamycin was the safest for the rice leaffolder larvae. Much higher larva survival was observed for the larvae fed on diets containing natamycin as an antifungal agent (59 and 72% at 200 and 400 ppm, respectively). Two agricultural fungicides, tebuconazole and azoxystrobin, are also potent as mold inhibitors when used in insect diets. The mixed use of natamycin and sorbic acid, or methylparaben, and the mixed use of sorbic acid and azoxystrobin resulted in significantly higher larva survival than sorbic acid + methylparaben. Natamycin + azoxystrobin and sorbic acid + tebuconazole resulted in larva survival similar to that of sorbic acid + methylparaben. The ternary combination of natamycin, sorbic acid, and methylparaben was the best combination for the rearing of rice leaffolder.
Insights
Natamycin is the safest mold inhibitor for rice leaffolder larvae, improving survival rates. Combinations with other agents, especially natamycin, sorbic acid, and methylparaben, offer the best solution for insect mass rearing challenges.
Area of Science:
- Agricultural Science
- Entomology
- Mycology
Background:
- Mold contamination poses significant challenges in insect mass rearing, impacting larval development and survival.
- Commonly used antifungal agents like sorbic acid and methylparaben can negatively affect lepidopteran larvae, hindering efficient rearing of species such as the rice leaffolder, *Cnaphalocrocis medinalis*.
- Identifying safe and effective mold inhibitors is crucial for optimizing insect rearing protocols.
Purpose of the Study:
- To screen various antifungal agents for their efficacy in inhibiting *Aspergillus niger* growth in insect diets.
- To evaluate the impact of different mold inhibitors on the survival and development of rice leaffolder larvae.
- To determine the optimal antifungal agent or combination for mass rearing of *Cnaphalocrocis medinalis*.
Main Methods:
- Screening of 19 antifungal agents (food preservatives, antifungal drugs, agricultural fungicides) for *Aspergillus niger* inhibition.
- Larval survival assays using artificial diets containing selected mold inhibitors at various concentrations.
- Evaluation of single-agent and combination treatments, including ternary mixtures, for their impact on rice leaffolder larvae.
Main Results:
- Most tested chemicals were unsuitable for rice leaffolder diets; sorbic acid and methylparaben significantly reduced larval survival.
- Natamycin demonstrated the highest safety and efficacy, with significantly improved larval survival at 200 and 400 ppm.
- Agricultural fungicides tebuconazole and azoxystrobin showed potent mold inhibition. Combinations, particularly ternary mixtures involving natamycin, sorbic acid, and methylparaben, enhanced larval survival compared to traditional agents.
Conclusions:
- Natamycin is a safe and effective mold inhibitor for rice leaffolder mass rearing.
- Combination strategies, especially the ternary mix of natamycin, sorbic acid, and methylparaben, provide the best solution for controlling mold while ensuring high larval survival.
- This study offers a viable strategy to overcome mold contamination issues in the mass rearing of *Cnaphalocrocis medinalis*.
Related Concept Videos
01:15Antifungal Agents
01:28Fungal Phylum Ascomycota