Irineu Lorini

Ocorrência de Sitophilus zeamais Mots. (Coleoptera: Curculionidae) danificando a cultura da videira no Rio Grande do Sul

Vineyards are attacked by a series of pests that damage yield. In addition to the insects traditionally associated with the crop, the presence of Sitophilus zeamais Motschulsky, registered as a grain store pest, was observed damaging grapes near maturity. Direct damage is caused by perforation of the grapes and indirect damage from the proliferation of bacteria that multiply in the spilt juice, that lead to increased rot at harvest. In Vitis vinifera grape vines of the Cabernet Sauvignon cultivar, up to 80% of the grapes were damaged by insect attack in February 2003.

Efficacy of modified atmosphere packaging to control Sitophilus spp. in organic maize grain

O efeito da embalagem em atmosferas modificadas sobre os insetos Sitophilus spp. nos graos de milho orgânico foi estudado. Os graos de milho foram empacotados em cinco atmosferas iniciais diferentes de 20% de O2, ou 20, 40, 60, 80% de CO2 com balanco de N2. As embalagens foram armazenadas por 30 dias a 26oC. As concentracoes de CO2 e O2 foram monitoradas dentro das embalagens durante o armazenamento. As analises de teor de umidade, acidez e pH foram tambem realizados no primeiro e trigesimo dia. Os resultados mostraram que no quinto, decimo quinto e trigesimo dia de estocagem nao foram encontrados diferencas significativas nas porcentagens de insetos mortos quando CO2 foi usado. Os resultados relativos a progenie indicaram que no quinto dia o numero de insetos emergentes foi menor a 20, 60 e 80% CO2. A completa inibicao dos insetos foi atingida com 30 dias de exposicao em atmosferas de CO2.

Effect of the synergists piperonyl butoxide and DEF in deltamethrin resistance on strains of Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae)

Synergists are an important research tool in the laboratory to help to determine the mechanisms of resistance involved in a particular population. This kind of investigation has produced valuable results in understanding resistance to pesticides. The ability of these compounds in suppressing deltamethrin resistance on four strains of Rhyzopertha dominica (F.) was evaluated under laboratory conditions. Two susceptible strains, obtained from the eighth generation in laboratory without any selection were tested; other two resistant strains consisted in the fifth deltamethrin selected generation. Each strain was bioassayed on filter paper impregnated with deltamethrin associated with a synergist in different proportions, following the methods recommended by FAO for assessing resistance. The synergists tested were piperonyl butoxide (PBO) and S,S,S-tributyl phosphorotrithioate (DEF), at the following proportions 1:0, 1:5, 1:10 and 1:15 of deltamethrin and the synergist, respectively. Both synergists showed a role in blocking enzymes involved in detoxifying deltamethrin. PBO conferred up to 27 times higher toxicity ratios in the resistant strains than in the susceptible ones. DEF was less effective in reducing the lethal dose of deltamethrin with ratios up to five times.

Rearing method of Oryzaephilus surinamensis (L.) (Coleoptera, Silvanidae) on various wheat grain granulometry

Oryzaephilus surinamensis e uma das especies de insetos-praga mais comuns em graos e outros produtos armazenados, e tem ocorrido em grandes populacoes em praticamente todas as unidades de armazenamento de graos. Contudo, a criacao massal deste inseto, em laboratorio, para bioensaios diversos, nao tem sido uma tarefa simples, em funcao de seu comportamento alimentar, tamanho reduzido e alta mobilidade. Assim, o objetivo deste trabalho foi desenvolver um metodo simples e eficiente para a criacao de O. surinamensis, usando graos de trigo moidos a diversas granulometrias para obter grandes populacoes e estagios padronizados para bioensaios. Insetos adultos foram coletados em diversos armazens na regiao sul do Brasil; 100 especimes foram colocados em frascos de vidro, com graos de trigo moido a diferentes graus, mantidos a 25±0.5oC e 65±5% de umidade relativa. Os insetos foram mantidos por 10 dias para copula e postura dos ovos, sendo entao removidos. Ovos, larvas e pupas foram contados a intervalos de cinco dias; a longevidade dos adultos da segunda geracao foi avaliada. Os graos moidos a grau 20 representaram o melhor meio para a producao de progenie: 89% dos ovos foram produzidos no 5o dia; 30,5% das larvas no 10o; 43% das pupas no 30o e aproximadamente 63% dos adultos no 46o. Os adultos sobreviveram ate 450 dias. A criacao de O. surinamensis, nas condicoes descritas e transferindo os adultos apos 10 dias e repondo o meio quando a populacao aumenta muito, produzira um numero de insetos de cada estagio suficiente para diversos bioensaios de laboratorio.

Comportamento de adultos de diferentes raças de Rhyzopertha dominica (Fabricius) (Coleoptera, Bostrichidae) em superfície tratada com deltamethrin

The most important pest of stored wheat in Brazil, Rhyzopertha dominica (Fabricius, 1792), was tested at Embrapa Trigo, in Passo Fundo-RS, on filter paper impregnated with LC5, LC25, and LC50 of deltamethrin to verify alterations in its walking behaviour that may contribute for pest resistance management in grain storage. Insects of four strains were used, two resistant, BR6 and BR12, and two susceptible, BR4 and UK1, which were collected in storage facilities in Rio Grande do Sul and reared in the laboratory. Insects of the UK1 strain were brought from the laboratory of the Imperial College of Science and Technology, United Kingdom. The results showed differences in the walking behaviour between individuals of strains during the 24 h of the assessment period. Insects of the resistant strains reduced their walking activities on contaminated surface, in an attempt to avoid the insecticide .

The cross-resistance spectrum in deltamethrin resistance strains of Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae)

Objetivou-se verificar a existencia de resistencia cruzada em racas de Rhyzopertha dominica (F.) resistentes ao inseticida deltametrina. Os experimentos foram conduzidos testando outros tres inseticidas, tambem usados para controlar pragas de graos armazenados, como permetrina (piretroide), pirimifos-metil e clorpirifos-metil (organofosforados). Quatro racas da praga foram usadas: duas racas suscetiveis, BR4 e UK1, e duas racas resistentes, BR6 e BR7, todas mantidas em laboratorio apos a coleta nos armazens. Inicialmente todas as racas foram avaliadas em sua susceptibilidade ao inseticida deltametrina. Posteriormente, cada raca foi submetida a pressao de selecao ao inseticida deltametrina por tres geracoes consecutivas e no final da terceira geracao cada raca foi avaliada em sua suscetibilidade com todos os inseticidas para determinar a resistencia cruzada. Os resultados mostraram a existencia de resistencia cruzada para o inseticida permetrina, nas racas BR6 e BR7 de R. dominica. Nao houve resistencia cruzada aos dois inseticidas organofosforados testados. Isso indica que a resistencia cruzada ocorreu dentro do mesmo grupo quimico de inseticidas e nao entre diferentes grupos.

Efeito do sinergista butóxido de piperonila na resistência de Oryzaephilus surinamensis (L) (Coleoptera, Silvanidae) a deltametrina e fenitrotiom

The use of synergists is an important tool to determine resistance mechanisms in insect species. In this research, the synergist piperonyl butoxide (PBO) was used, in different proportions, to evaluate the relative contribution of oxidase enzymes in the metabolism of the organophosphorous insecticide fenitrothion and the pyrethroid deltamethrin, on four Oryzaephilus surinamensis strains: OS1 (susceptible) and OS2, OS3 and OS4 (resistants). The synergist increased deltamethrin toxicity significantly in resistant strains, indicating that oxidases play an important role in deltamethrin resistance. On the other hand, PBO showed antagonistic effect to fenitrothion, reducing its toxicity significantly, indicating that this synergist is not adequate for mixtures with organophosphorous compounds.

Chemical and energy composition of corn harvested with various moisture levels and different drying temperatures to broiler chickens

The experiment was conducted to evaluate the effects of moisture levels at harvest and drying temperatures of corn on its chemical composition and apparent metabolizable energy corrected to zero nitrogen retention (AMEn) to broiler chickens. The corn was harvested with 35%, 25%, 18%, 15.3% and 14.3% of moisture and submitted to drying temperatures of 100, 70 and 40 oC. The moisture levels of 15.3% and 14.3% of corn were not submitted to drying and the last value represented the treatment post-harvesting (60 days after the first harvest). The chemical composition was determined by AOAC (1995) and AMEn assay was carried out by total collection procedure as described by Hill and Anderson (1958) and methodology of Matterson et al. (1965). When the AMEn values were considered on as fed basis, significant differences occured between the treatment of corn no drying and the others. The mean AMEn value was 11.8% less in energy (2864kcal/kg) relative to the highest value (3247kcal/kg).This is due to grain humidity having reached 24% on that treatment caused by natural grain natural re-hydration. When the energy values of corn were changed to dry-matter basis, there were no differences among the treatments. There were no major changes in nutritive value of corn harvested with different moisture levels and submitted to various drying temperatures, compared to expected standards, except the AMEn value (as fed basis) when the corn was no drying.

Efeito de repelência do inseticida deltamethrin sobre insetos de raças resistentes e suscetíveis de Rhyzopertha dominica (F.) (Coleoptera, Bostrichidae) em grãos de trigo armazenado

This research was carried out in order to study the effect of repellency of the insecticide deltamethrin against the lesser grain borer, Rhyzopertha dominica (F.). Four strains of R. dominica were used: two of them were deltamethrin resistant, BR6 and BR12, and two were susceptible, BR4 and UK1. The insects were collected in storage units and maintained in laboratory. One hundred insects were released in the bottom of a plastic pot containing untreated wheat grain connected to another pot of same size containing wheat grain treated with LC5, LC25, LC50, separately, for each strain, replicated four times. The pots were kept horizontally in order to let the insects to move freely between the two compartments, at 25±1oC and 60±5% of temperature and relative humidity, respectively. The assessment of insect distribution in the pots was performed 12 days after the releasing. The insects avoided the treated grain at all concentrations, meaning that the insecticide presents an effect of repellency against the insects. Nevertheless, there were no significant differences in the number of individuals of the susceptible strains between the treatments and the control. On the other hand, the resistant strains showed higher response to deltamethrin than the susceptible insects, especially at higher concentrations. The study of such behavior is fundamental for decision making in resistance management programs of stored product insects.

Potencial de desenvolvimento de Lasioderma serricorne (Fabricius, 1792) (Coleoptera: Anobiidae) em dietas contendo soja

Lasioderma serricorne is a worldwide pest with great potential for adaptation to a wide variety of food products of vegetable origin. It has frequently been found in stored soybeans, causing concern to warehouse managers. This study aimed to determine the potential for adaptation of L. serricorne in soybean based products, studying the development of this insect in different soybean diets, evaluating the number and intensity of emerging adults and the duration of the life cycle from eggs to adults. The insects were submitted to the following diets: 1) whole soybeans + broken soybeans (proportion of 3:2); 2) soybean flour + brewer’s yeast (proportion of 5:1); 3) soybean flour + wheat germ + brewer’s yeast (proportion of 5:2:1); and 4) corn flour + wheat germ + brewer’s yeast (proportion of 5:2:1), and to evaluate adult survival, a control treatment with no food was added. The results showed that L. serricorne is an insect that develops and completes its life cycle in diets containing soybean, and could become a pest with economic importance in foods. The best diet for rearing L. serricorne was that containing soybean flour + wheat germ + brewer’s yeast (proportion of 5:2:1) with a peak of adult emergence 49 days after laying, starting as from 42 days and continuing up to 73 days after laying. L. serricorne adults survived for up to 38 days with no food but only 20 to 22 days on diets based on soybeans, soybean flour, wheat germ, brewer’s yeast and corn flour.