Long-term effectiveness of two graphene formulations against two major stored product insects

Abstract

This paper evaluated two graphene formulations' (Gr1 and Gr2) insecticidal and long-lasting effects, against the adults of the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Tenebrionidae) and the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychiidae) on soft wheat kernels. Graphene-dusted wheat kernels at 500 and 1000 ppm were preserved at 25 °C with 55 % relative humidity (RH). Samples were collected on the initial day of the store and thereafter every 30 days for 180 days until the duration of the storage was completed. For each intervals, adults of each insect species were added to samples of treated and untreated wheat, while after exposure for 7, 14, and 21 days, adult mortality was recorded. The results indicated that both graphene formulations were very effective against both insect species and provided long-term protection even at the last bioassay. Gr1 was more effective in comparison with Gr2 at 500 ppm for R. dominica, while both formulations worked just as well at 1000 ppm for both species. Furthermore, both doses and formulations effectively controlled adults of S. oryzae, while 1000 ppm of Gr2 was required for complete control of R. dominica. This study is the first that examined the residual efficacy of graphene formulations on wheat against stored-grain insect species showing noticeable protective potential of the two graphene formulations. Additional experiments need to be performed to assess the practical viability of using this novel and non-toxic material for a chemical-free control plan for postharvest management of durable agricultural products.