The performance of spintor dust and actellic 2% dust for managing Sitophilus zeamais (Motschulsky) (Coleoptera, Curculionidae) in different maize varieties in the Niger delta

Potency of two insecticides (Actellic 2% dust and Spintor dust at 0.02g/20 g maize grains) in managing Sitophilus zeamais in stored maize was evaluated using three varieties (Bende, Ogbia muno, and ACR 97 TZL Comp. 1-W) under prevailing laboratory conditions (25-30OC and 70-90 % R. H.). Four pairs of 7-day old S. zeamais adults were introduced on each of the four 20 g lots of each variety in 1-L Kilner jars. Adult progeny, weight loss and developmental periods were assessed. The interactive effect of the insecticides and maize variety under investigation showed that considerably more adult progeny developed in control jars than in jars containing maize treated with test insecticides. Weight losses for one generation of infestation by S. zeamais in maize treated with Spintor dust, Actellic 2% dust and insecticide free maize were 8%, 12% and 14 %, respectively. Adult progeny development period was ranked in a decreasing order as Spintor dust < Actellic dust < Untreated maize. The use of Spintor dust as a pesticide for managing stored maize by S. zeamais is being reported, perhaps, for the first time to me.Key words: Sitophilus zeamais; Actellic dust; Spintor dust; Maize variety; Infestation

Toxicidade de óleos essenciais de Piper aduncum e Piper hispidinervum em Sitophilus zeamais Toxicity of essential oils of Piper aduncum and Piper hispidinervum against Sitophilus zeamais

Óleos essenciais de Piper aduncum L. e Piper hispidinervum C.DC. (Piperaceae) foram avaliados quanto ao efeito inseticida em Sitophilus zeamais Motsch. por ação de contato, fumigação e tópica. Na determinação da DL50 e CL50, foi utilizada a análise de Probit. Médias porcentuais de mortalidade dos insetos foram comparadas por meio da análise de regressão linear e superposição das barras do erro padrão. S. zeamais foi mais suscetível ao efeito de contato do óleo de P. hispidinervum em relação ao de P. aduncum, obtendo-se CL50 de 0,51 e 2,87 mL cm- 2 de óleo, respectivamente. Mortalidade próxima a 100% foi obtida nas concentrações de 20 e 30% do óleo de P. hispidinervum. Quanto ao efeito fumigante, a susceptibilidade foi maior no óleo de P. aduncum do que no de P. hispidinervum. Houve diferença significativa entre os óleos somente nas concentrações de 0,1 e 1,0. A DL50 foi semelhante nos dois óleos essenciais por aplicação tópica. No entanto, a mortalidade foi maior com P. aduncum. Óleos essenciais de P. aduncum e P. hispidinervum possuem efeito inseticida em S. zeamais, mas as respostas dependem da concentração e do método de exposição a que o inseto seja submetido.<br>Essential oils of Piper aduncum L. and Piper hispidinervum C. DC. (Piperaceae) were tested against Sitophilus zeamais Motsch. Contact, fumigant toxicity and topical effect were tested. Probit analysis was employed in evaluating the LC50 and LD50 response. Linear regression analysis and superposition of the bars (means error standard) were used for comparison of means percentage mortality. S. zeamais was more susceptible to the contact toxicity of the P. hispidinervum oil than P. aduncum oil with LC50 values of 0.51 and 2.87 mL cm-2 of the oil, respectively. The mortality rate was nearly 100% at P. hispidinervum oil concentrations of 20 and 30%. With respect to the fumigant action, the weevil was more susceptible to the P. aduncum oil than to P. hispidinervum. A significant difference between oils mortality was observed only at 0.1 and 1.0% concentrations. For topical effect, similar values of the LD50 were obtained for essential oils. However, the mortality was higher with P. aduncum. Essential oils of the P. aduncum and P. hispidinervum possess insecticidal effect from S. zeamais, but the responses varied according to concentration of the oils and exposure methods