Preliminary Evaluation of Plasma-Activated Fog Treatment Against Callosobruchus Maculatus (Chrysomelidae: Bruchinae)

The Leguminosae family is a key source of plant proteins, particularly in developing countries and healthy diets. Postharvest losses are mainly due to pests and diseases. The Callosobruchus genus, including the cowpea weevil Callosobruchus Maculatus (F.) (Coleoptera: Bruchidae), is a major pest causing global damage to stored products. It lays eggs on legume seeds that hatch in storage, leading to rapid multiplication under favorable conditions and up to 80% grain losses. Different kinds of direct and indirect damages occur during infestation. First, this beetle consumes the endosperm of grains causing grain weight loss associated with a nutritional value decline, quality deterioration, and exasperation of agronomic properties like seed viability and vigor reduction. Moreover, infestations also cause contamination through feces, eggs, larval molts, empty cocoons, and dead adults. Not to be underestimated is their potential to spread fungal pathogens, hence increasing mycotoxin contamination, making grain quality preservation and food availability a constant concern, especially for consumers' health. Innovative control strategies are urgently needed to address consumer concerns, and to limit unwanted consequences of chemical control means such as environmental degradation and the development of insect resistance. Low Temperature Plasma (LTP) is currently proposed as a novel promising technique against microbial and chemical contamination of products and innovative pest control agents. It can be applied either directly on product surfaces or indirectly through a plasma-activated medium. In this preliminary study, Plasma Activated Fog (PAF) was generated using a volume dielectric barrier discharge and a glass aerosol nebulizer and applied to evaluate the effect on C. maculatus. We evaluated the ovicidal and adulticidal effects of PAF and the long-term effects of treatments over the newborn adults from the treated chickpea (Cicer arietinum L.) seeds. No statistical differences were observed between the PAF and the control treatments regarding the mortality of adults exposed for 10, 20, and 30 minutes to PAF. On the other hand, fertility trials showed a significant effect of PAF, to treatment time: PAF led to substantial oviposition reduction, and this effect was stronger right after the treatment and it decreased over time. We further observed a significant reduction in the number of larvae hatched from the eggs treated by PAF compared to the control. Our preliminary results show that PAF treatment probably induces more sublethal (indirect) than lethal effects on insects, as exhibited in the number of eggs laid and the number of eggs hatched. The results obtained in the present work hold the potential to optimize PAF treatment conditions for more effective insecticidal use. ACKNOWLEDGMENTS: Funded by NextGenerationEU, MUR-Fondo Promozione e Sviluppo - DM 737/2021, PlaTEC -– CUP H99J21017820005