Compounds from Brazil nuts and their effects on Sitophilus zeamais (Coleoptera: Curculionidae) survival in bulk ground feed

Abstract Sitophilus zeamais is a pest in several stored agricultural products, but presents difficulty feeding on Brazil nuts (Bertholletia excelsa H.B.K). Even when certain bulk bran feeds are unsuitable for its development, it may be found in these products, especially when stored near corn grain. Feed used for young pigs requires special care due to possible contamination, with S. zeamais being an important vector for microorganisms, especially fungi. The objective was to investigate aspects related to fractions or compounds present in Brazil nut that can interfere with S. zeamais feeding. A corn based commercial feed combined with Brazil nut compounds in different formulations was offered to adults of S. zeamais to evaluate the survival of this insect. Treatments consisted of: T1 (control = animal feed (from market) for pigs); T2 (animal feed + in natura nuts); T3 (animal feed + 60% added nuts oil); T4 (animal feed + defatted nuts); T5 (animal feed + fixed mineral residue from nuts). The presence of nuts oil was found to reduce S. zeamais survival, with high mortality rates, especially in treatments that contained higher concentrations of these compounds, since the raw chestnut also contains high levels of oil. In treatments T1(control = animal feed (from market) for pigs) and T5 (animal feed + fixed mineral residue from nuts), that contain no nut oil, insects survived longer. After elemental analyses, given the dynamics observed in each treatment and their association with the potential toxic effects, none of the compounds present in the respective nut fractions could be associated with insect mortality, leaving only the association with the presence of nut oil in the substrates. Further research into nut oil should are necessary, as it demonstrates potential for the control of S. zeamais in bulk animal feed and in stored corn, aiming for the development of sustainable and less toxic alternatives for the management of this pest.