Laboratory evaluation of four types of biochar to manage some stored product insects

Abstract

Four types of biochars were prepared from rice husk as farm waste, sugarcane bagasse as sugar cane juice store waste, residues of Leucaena leucocephala tree as horticulture waste and chicken manure as chicken farm reduce at 700οC, then evaluated as a alternative to control Tribolium castaneum, Rhyzopertha dominica, Oryzaephlius surinamensis and Sitophilus oryzae. The character of each type has been defined using Scanning Electron Microscopy (SEM) with an Energy Dispersive X-Ray Analysis (EDX) and Fourier transform infrared spectroscopy (FTIR) were used to identify the elemental composition and functional groups distributed on biochars surface. The elemental compositions refer to the chicken manure biochar exhibited a decrease in Carbon concentration and increase Oxygen content; there is a negative correlation between C and O contents. On the other hand, the chicken manure biochar is the only tested biochar that contains Ca, P, and Cl. The chicken manure biochar has the largest number of functional groups on its surface, the mortality of insects was recorded after 10 days which showed that the chicken manure biochar was the most effective which contains more different elements and functional groups on its surface. The most affected insects were O.surinamensis and R. dominica with mortality percentages 86.66 and 73.33. Smaller particles of chicken manure biochar were more effective than larger particles against both R. dominica and O. surinamensis, the smaller particles (1.80—0.94 µm) recorded LC50 1.29 and 0.56 g/kg against R. dominica and O. surinamensis. SEM images for the affected insects showed the adhesion of biochar particles on insect’s body parts, also, the sensilla were disappeared as a result of the friction between biochar particles and insect cuticle. Our results may indicate the promising features of biochar as an alternative method to control some stored product insects with considering the source of biochar which affect its elemental and functional groups contents. Biochar had different efficacy depending upon its moisture contents, with increased moisture the toxicity of biochar decreased.