The objective of this work was to evaluate the contact toxicity of essential oil of Croton pulegiodorus Baill on six populations of Sitophilus zeamais Motschulsky. The S. zeamais populations used were from Crixás-GO, Espírito Santo do Pinhal-SP, Juiz de Fora-MG, Picos-PI, Serra Talhada-PE, and Vicentina-MS, Brazil, and present different susceptibility to synthetic insecticides. The essential oil of C. pulegiodorus used was obtained from plants collected in Triunfo-PE, Brazil. The lethal concentrations (LC50 and LC90), toxicity ratio of the essential oil, and the resistance ratio of the populations were estimated. The S. zeamais population from Serra Talhada-PE presented the lowest LC50 (4.21 μL 20 g-1) and LC90 (6.67 μL 20 g-1) and was the reference for susceptibility to the essential oil of C. pulegiodorus. The S. zeamais population from Espírito Santo do Pinhal-SP presented the highest LC50 (6.02 μL 20 g-1) and LC90 (10.55 μL 20 g-1) and was the reference for tolerance to the essential oil of C. pulegiodorus. The toxicity ratio ranged from 1.01 (Picos-PI) to 1.43 (Serra Talhada-PE); and the resistance ratio ranged from 1.13 (Crixás-GO) to 1.43 (Espírito Santo do Pinhal-SP). The essential oil of C. pulegiodorus reduced the emergence of adult S. zemais and showed residual effect, with contact toxicity, after 30 and 60 days of application.

Foi avaliada a toxicidade, por contato, a taxa de oviposição e emergência de C. maculatus em grãos de feijão-caupi tratados com o óleo essencial de Croton blanchetianus e o efeito residual em diferentes períodos de armazenamento, sendo, ainda, determinadas as concentrações letais (CL₅₀ e CL₉₀). O teste de toxicidade por contato e taxas de oviposição e emergência de C. maculatus foi realizado em placas de Petri, utilizando 6 concentrações (0; 2.5; 5; 7.5; 10 e 12.5 μL/20g). No teste residual, os grãos foram submetidos a diferentes períodos de armazenamento (0, 30 e 60 dias). Os resultados mostraram que o óleo essencial de C. blanchetianus apresentou toxicidade por contato sobre C. maculatus. Observou-se que as concentrações letais foram consideradas baixas. Este óleo também reduziu a oviposição e emergência de adultos. Por outro lado, durante diferentes períodos de armazenamento o óleo teve sua ação diminuída, apresentando potencial para ser utilizado em programas de manejo de C. maculatus em feijão armazenado. Palavras-chave: inseticidas botânicos; Bruchinae; grãos armazenados; Vigna unguiculata. BIOACTIVITY OF Croton blanchetianus Baill (Euphorbiaceae) ESSENTIAL OIL ON THE Callosobruchus maculatus Fabricius, 1775 (Coleoptera: Chrysomelidae) ABSTRACT: The toxicity was calculated by contact, the oviposition and emergence rate of C. maculatus on cowpea treated with the essential oil of Croton blanchetianus and the residual effect in different periods of storage, and additionally the lethal concentrations (CL₅₀ and CL₉₀) were determined. The contact toxicity test and order to the oviposition and emergence rates of C. maculatus was carried out in Petri dishes, using 6 concentrations (0, 2.5, 5, 7.5, 10 and 12.5 μL/20g). In the residual test, the cowpeas were submitted to different storage periods (0, 30 and 60 days). The results showed that the C. blanchetianus essential oil showed contact toxicity on the beetle C. maculatus. It was observed that lethal concentrations were considered low. This oil also reduced oviposition and emergence of adults. On the other hand, during different periods of storage the oil's action diminished, presenting potential to be used in management programs of C. maculatus in stored beans. Keywords: botanical insecticides; Bruchinae; stored grains; Vigna unguiculate.

The lesser mealworm, Alphitobius diaperinus, is a widespread pest in poultry farming, causing economic losses and facilitating the spread of pathogens. Current control methods rely heavily on synthetic insecticides, which raise environmental concerns and contribute to resistance. This study investigated the insecticidal potential of Moringa oleifera seed preparations, including an aqueous extract (AE), a protein-enriched fraction (PF), and an isolated lectin (WSMoL), against A. diaperinus. Contact assays demonstrated that AE and PF reduced adult survival by up to 90% and 100%, respectively, while WSMoL was effective only against larvae, causing 48% mortality. Ingestion assays showed that AE and PF reduced adult survival by 60% and 30%, respectively; impaired diet utilization; and caused significant weight loss. WSMoL exhibited antinutritional effects, including a 94% reduction in trypsin-like activity, but did not cause lethality, although it may impair long-term survival. Midgut histological analysis revealed epithelial disorganization, vacuolization, and nuclear condensation in the treated insects. These findings suggest that M. oleifera seed preparations are promising candidates for sustainable pest control, offering both lethal and sublethal effects on A. diaperinus. Future research should focus on the development of formulations and long-term impact assessments on pest populations and non-target organisms, paving the way for eco-friendly alternatives in integrated pest management.

In this study, we evaluated the susceptibility of Alphitobius diaperinus larvae and adults to saline extract (SE), lectin-rich fraction (FR), and isolated lectin (MvRL) from Microgramma vacciniifolia rhizomes. To determine immediate effects, larvae and adults were exposed to SE (10.5 mg/mL), FR (7.5 mg/mL), or MvRL (1.0 mg/mL) for 48 h. Live insects were evaluated for acetylcholinesterase (AChE) activity. The delayed effects of SE (10.5 mg/mL), FR (7.5 mg/mL), and MvRL (0.2 and 0.4 mg/mL) were checked by incubating the adults for 16 days with a diet containing the preparations. In vitro effects on gut digestive enzymes were investigated. All preparations showed immediate larvicidal effect but had no effect on adult survival. Extracts from FR-treated larvae showed higher AChE activity than control insects. In the delayed effect assay, the adults lost biomass after consuming SE and FR. FR was the most effective inhibitory agent of trypsin-like and amylase activities (88% and 65% inhibition, respectively). All preparations inhibited endoglucanase activity in 94–98%, while SE and FR inhibited exoglucanase activity in 93.2 and 94.1%, respectively. In conclusion, M. vacciniifolia rhizomes contain compounds (including MvRL) that affect the survival and physiology of A. diaperinus, acting as potential natural insecticides for controlling this pest.