Resumo A possível interferência de populações de pragas resistentes na ação de inimigos naturais ainda não foi esclarecida. Assim, este trabalho teve como objetivo avaliar o desempenho de Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) em ovos de Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) com frequência de resistência à Metaflumizona ao longo de seis gerações de exposição ao produto. Cartelas (2,0 x 7,0 cm) com ovos de duas populações de S. frugiperda, (resistente à Metaflumizona e outra suscetível), foram expostas às fêmeas de T. pretiosum por 24 horas em condições de livre escolha e sem chance de escolha por três gerações (G1, G4 e G6). O delineamento experimental foi inteiramente casualizado com 25 repetições, sendo cada repetição composta por uma cartela (unidade experimental) contendo 20 ovos. Os parâmetros avaliados foram: parasitismo (%), emergência (%), razão sexual, número de parasitoides emergidos por ovo e longevidade de machos e fêmeas. ANOVA e teste de Tukey (P≤ 0,05) foram aplicados aos dados coletados. Os resultados mostraram redução do parasitismo [41,0% (G1) e 28,4% (G4)], emergência de ovos (17,5%) e parasitoides/ovo [16,2 (G4) e 17,2 (G6)] em ovos oriundos da população com frequência de resistência. As fêmeas emergidas de ovos da população G6 sem exposição à Metaflumizona, tiveram maior longevidade (3,5 dias a mais) do que a população exposta ao inseticida. A razão sexual e a longevidade de machos não foram afetadas. Os resultados indicam uma redução na atividade de T. pretiosum se as populações de S. frugiperda apresentarem alguma frequência de resistência à Metaflumizona.

Abstract The possible interference of resistant pest’s populations to insecticides in natural enemies in the action thas not been clarified yet. Thus, this study aimed to evaluate Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) performance on Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) eggs with resistance frequency to the Metaflumizone over six generations of product exposure. Egg cards (2.0 x 7.0 cm) containing eggs from two populations of S. frugiperda, (resistant to Metaflumizone and the other susceptible), were exposed to T. pretiosum females for 24 hours in free-choice and no-choice testing in three generations (G1, G4, and G6). A completely randomized experimental design was used with 25 replications, each consisting of an egg card (experimental unit) containing 20 eggs. The parameters evaluated were: parasitism (%), emergence (%), sex ratio, number of emerged parasitoids per egg and males/females longevity. ANOVA and Tukey test (P≤ 0.05) were applied on the results. Results showed a reduction in parasitism [41.0% (G1) and 28.4% (G4)], egg emergence (17.5%) and parasitoids/egg [16.2 (G4) and 17.2 (G6)] in eggs originating from the population with resistance frequency. Females emerging from G6 populations eggs without exposure to Metaflumizone had greater longevity (3.5 days more) than the resistant population. The sex ratio and male longevity were not affected. The results indicate a reduction in T. pretiosum activity if S. frugiperda populations have some frequency of resistance to Metaflumizone.

RESUMO: Avaliamos em condições de campo a toxicidade de inseticidas previamente identificados como nocivos em bioensaios de laboratório e semicampo sobre o parasitóide Trichogramma pretiosum (Hymenoptera: Trichogrammatidae). Os experimentos foram conduzidos durante as safras 2019/20 e 2020/21 em lavouras de arroz. Seguindo as recomendações da International Organization for Biological and Integrated Control (IOBC), quatro inseticidas foram aplicados em parcelas experimentais de 64 m2. Posteriormente, realizou-se uma liberação inundativa de T. pretiosum. Para verificar as taxas de parasitismo, aos 1, 2, 4 e 6 dias após a liberação (DAR) dos parasitoides, ovos do hospedeiro Ephestia kuehniella (Lepidoptera: Pyralidae) foram ofertados. Após a determinação do número de ovos parasitados, os dados foram agrupados em um coeficiente de redução (Ex) para fornecer um resultado único para os efeitos dos inseticidas sobre o parasitoide. Tanto para as safras 2019/20 quanto 2020/21, verificou-se que em 2 DAR, ocorreram as maiores taxas de parasitismo. Em contraste, aos 6 DAR, não foram observadas taxas de parasitismo. Lambda-cialotrina, tiametoxam e zeta-cipermetrina foram classificados como moderadamente nocivos; tiametoxam + lambda-cialotrina foi classificado como prejudicial. Seguindo as diretrizes da IOBC, a toxicidade desses produtos em condições de campo é inferior à obtida em laboratório ou semi-campo para o T. pretiosum. Entretanto, esses inseticidas devem ser evitados, ou utilizados em momentos que não coincidam com a liberação ou presença do parasitoide a campo.

ABSTRACT: We evaluated under field conditions the toxicity of insecticides previously identified as harmful in laboratory and semifield bioassays on the parasitoid Trichogramma pretiosum (Hymenoptera: Trichogrammatidae). The experiments were conducted during the 2019/20 and 2020/21 harvests in rice fields. Following the recommendations of the International Organization for Biological and Integrated Control (IOBC), four insecticides were applied in 64 m2 experimental plots. Subsequently, T. pretiosum was released inundatively. To verify parasitism rates, at 1, 2, 4 and 6 days after release (DAR) of the parasitoids, eggs from the host Ephestia kuehniella (Lepidoptera: Pyralidae) were offered. After determining the number of parasitized eggs, the data were grouped into a reduction coefficient (Ex) to provide a single result for the effects of the insecticides on parasitoid. For both the 2019/20 and 2020/21 evaluated crops, it was found that at 2 DAR, the highest parasitism rates occurred. In contrast, in 6 DAR, no parasitism rates were observed. Lambda-cyhalothrin, thiamethoxam, and zeta-cypermethrin were classified as moderately harmful; thiamethoxam + lambda-cyhalothrin was classified as harmful. Following IOBC guidelines, the toxicity of these products under field conditions is lower than that obtained in the laboratory or semi-field for the T. pretiosum. However, these insecticides should be avoided, or used at times that do not coincide with the release or presence of the parasitoid in the field.

Resumen Introducción. El perforador del fruto del tomate Neoleucinodes elegantalis (Guenée) (Lepidoptera: Pyralidae) y los minadores de la hoja Phthorimaea operculella (Zeller) y Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), afectan la producción de tomate en diferentes áreas en Venezuela. El parasitismo de sus huevos por Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) es una valiosa alternativa de control de bajo costo y sustentable que combinado con otras formas de control sería un excelente componente del Manejo Integrado de Plagas. Objetivo. Evaluar el parasitismo ejercido por T. pretiosum sobre las poblaciones de plagas lepidópteras en tomate. Materiales y métodos. La evaluación se realizó en todas las siembras entre junio y agosto de 2017, desde la tercera semana después del trasplante hasta dos semanas después de la última floración, en las localidades El Pueblito, Los Ejidos del Hato y El Vigiadero, municipio Jiménez, estado Lara, Venezuela. Se liberaron los adultos del parasitoide y posteriormente, se recolectaron los foliolos para evaluar el parasitismo de los huevos de las especies minadoras. Al iniciarse la fructificación, se colectaron frutos pequeños y medianos incluyendo el cáliz y fueron cortados cuidadosamente del pedúnculo floral. En ambos casos se realizó el conteo de los huevos. Resultados. En todas las evaluaciones, se registró un parasitismo que varió en 43 y 53 % para N. elegantalis y entre 16 y 48 % para las especies minadoras de las hojas. En el laboratorio, el parasitismo para P. operculella y T. absoluta varió entre 88 y 84 % cuando los huevos estuvieron separados, al estar juntos se observó un mayor parasitismo de huevos de P. operculella (76 %) versus T. absoluta (44 %). Conclusiones. T. pretiosum ejerció un parasitismo significativo sobre los huevos de las tres especies lepidópteras estudiadas en siembras de tomate en Venezuela.

Abstract Introduction. The tomato fruit borer Neoleucinodes elegantalis (Guenée) (Lepidoptera: Pyralidae), and the leafminers Phthorimaea operculella (Zeller) and Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), affect tomato production in different areas in Venezuela. The parasitism of their eggs by Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) is a valuable low-cost and sustainable control alternative that combined with other forms of control would be an excellent component of Integrated Pest Management. Objective. To evaluate the parasitism exerted by T. pretiosum on the lepidopteran pest populations in tomato. Materials and methods. The evaluation was carried out in all sowings between June and August 2017, from the third week after the transplant until two weeks after the last flowering, in the localities of El Pueblito, Los Ejidos del Hato, and El Vigiadero, Jiménez municipality, Lara state, Venezuela. Parasitoid adults were released and subsequently leaflets were collected to evaluate the parasitism of the eggs of the leafminer species. At the onset of fruiting, small and medium-sized fruits including the calyx were collected and carefully cut from the floral peduncle. In both cases, eggs were counted. Results. In all evaluations, a parasitism varied between 43 and 53 % for N. elegantalis, and between 16 and 48 % for leafminer species was recorded. In the laboratory, the parasitism for P. operculella and T. absoluta ranged between 88 and 84 %, when eggs were separated, when eggs were together, a higher parasitism of P. operculella eggs (76 %) versus T. absoluta (44 %) was observed. Conclusions. T. pretiosum exerted a significant parasitism on the eggs of the three-lepidopteran species in tomato crops in Venezuela.

RESUMO A diversidade de artrópodes-praga tem exigido a integração de diferentes métodos de controle. Assim, aplicações de óleos essenciais com atividade inseticida, repelente ou fagoinibidora, associadas às liberações de inimigos naturais, podem potencializar o manejo integrado de pragas, desde que apresentem seletividade. Nesse contexto, o objetivo foi avaliar a seletividade dos óleos de alecrim-pimenta Lippia origanoides Kunth (Verbenaceae), citronela Cymbopogon winterianus Jowitt. (Poaceae) e capim-santo C. citratus (DC) Stapf., sobre Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae), comparando cinco concentrações (0,01; 0,05; 0,1; 0,5 e 1,0%), além da testemunha (detergente neutro à 1,0%). Avaliou-se a toxicidade residual por meio da mortalidade de adultos, calculando-se concentrações letais (CL50), além das reduções no parasitismo em ovos de Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) e seletividade aos parasitoides. Os três óleos exibiram seletividade ao parasitoide T. pretiosum, causando mortalidade entre 17,2 (alecrim-pimenta) e 32,2% (capim-santo), na menor concentração. Destacou-se o óleo essencial de alecrim-pimenta com CL50 de 0,43%, apenas 22% de redução do parasitismo (Classe 1 - Inócuo) e 88% de emergência quando à 0,01%. A CL50 do óleo de capim-santo foi 0,15%, com 34% de redução do parasitismo (Classe 2 - Levemente nocivo) e 74% de adultos emergidos. Já para o óleo de citronela, a CL50 foi de 0,12%, 46% de redução (Classe 2 - Levemente nocivo) e emergência de 62%. A seletividade dos óleos essenciais encontrada pode viabilizar liberações de T. pretiosum, integrando controle biológico e inseticidas botânicos, à medida que ovos não pulverizados, sejam parasitados por T. pretiosum.

ABSTRACT The diversity of arthropod pests has required the combined use of various control methods. The application of essential oils showing insecticidal, repellent or phage-inhibiting activity, together with the release of natural enemies, can improve integrated pest management provided the oils display selectivity. The aim of this study was to evaluate the selectivity of the oils of rosemary pepper [Lippia origanoides Kunth (Verbenaceae)], citronella [Cymbopogon winterianus Jowitt. (Poaceae)] and lemongrass [C. citratus (DC) Stapf.] for Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae), comparing five concentrations (0.01, 0.05, 0.1, 0.5 and 1.0%), and a control (neutral detergent at 1.0%). Residual toxicity was evaluated using adult mortality, calculating lethal concentrations (LC50) in addition to the reductions in parasitism in eggs of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) and selectivity for the par asitoids. The three oils showed selectivity for the parasitoid T. pretiosum, resulting in a mortality rate of between 17.2% (rosemary pepper) and 32.2% (lemongrass) at the lowest concentration. The essential oil of rosemary pepper stood out with an LC50 of 0.43%, a reduction of only 22% in parasitism (Class 1 - Innocuous) and 88.0% emergence, at a dose of 0.01%. The LC50 of the lemongrass oil was 0.15%, with a 34.0% reduction in parasitism (Class 2 - Slightly harmful) and 74.0% emerged adults. For the citronella oil, the LC50 was 0.12%, with a reduction of 46.0% (Class 2 - Slightly harmful) and emergence of 62.0%. The selectivity of the essential oils makes possible to release T. pretiosum, integrating biological control with botanical insecticides, as long as non-sprayed eggs are parasitised by T. pretiosum.

Resumo Espécies de Trichogramma Westwood, 1833 (Hymenoptera: Trichogrammatidae) são freqüentemente usadas como agentes de controle biológico contra Lepidoptera, esses endoparasitóides de ovos apresentam taxonomia complexa, o que dificulta sua aplicação prática. Este estudo teve como objetivo comparar seqüências de regiões espaçadoras internas transcritas de DNA ribossômico (ITS2-rDNA) de acessos de Trichogramma com aquelas depositadas no GenBank, a fim de avaliar a confiabilidade do ITS2 barcode para discriminar espécies e avaliar a diversidade genética. As seqüências de ITS2-rDNA obtidas de dezessete espécimes de Trichogramma confirmaram identidades anteriores com base em características morfológicas. O alinhamento de múltiplas sequências revelou a existência de regiões altamente conservadas nas sequências ITS2, enquanto o dendrograma indicou que os espécimes formavam três grupos compreendendo T. manicobai e T. marandobai (grupo I), T. galloi (grupo II) e T. pretiosum (grupo III). O marcador ITS2 mostrou ser um poderoso DNA barcode para discriminar espécies de Trichogramma podendo ser usado como complemento da abordagem morfológica.

Abstract Species of Trichogramma Westwood, 1833 (Hymenoptera: Trichogrammtidae) are frequently used as biological control agents against Lepidoptera, but practical application of these egg endoparasitoids are complicated because of their complex taxonomy. This study aimed to compare sequences of internal transcribed spacer regions of ribosomal DNA (ITS2-rDNA) of Trichogramma accessions with those deposited in GenBank in order to access the reliability of the ITS2 as a barcode for discriminating species and evaluating the genetic diversity. ITS2-rDNA sequences obtained from seventeen specimens of Trichogramma confirmed previous identifications based on morphological characteristics. Multiple sequence alignment revealed the existence of highly conserved regions in ITS2 sequences while the neighbour-joining dendrogram indicated that the specimens formed three clusters comprising T. manicobai and T. marandobai (group I), T. galloi (group II) and T. pretiosum (group III). The ITS2 marker was shown to be a powerful DNA barcode for discriminating Trichogramma species and could be used to complement the morphological approach.

Resumen El objetivo de este estudio fue evaluar el impacto de la temperatura en el desarrollo de dos líneas de Trichogramma pretiosum (Hymenoptera: Trichogrammatidae), para determinar los requisitos térmicos de este parasitoide en huevos de Neoleucinodes elegantalis (Lepidoptera: Crambidae). El experimento se llevó a cabo con dos líneas (“Ubajara” y “Guaraciaba”, Ceará) de T. pretiosum a partir de huevos parasitarios de N. elegantalis en frutos de tomate (Solanum lycopersicum). En este experimento, se usaron 40 huevos del huésped N. elegantalis y 4 hembras de los parasitoides, con exposición al parasitismo durante 24 horas (a 25 ± 1 °C, 70 ± 10 % de HR y fotofase de 12 h). Al final de este período, se retiraron las hembras y los tubos se transfirieron a incubadoras (HR = 70 ± 10 % y fotofase de 12 h, a 15, 20, 25, 30 o 35 °C, hasta la aparición de la generación siguiente de parasitoides. Los parámetros evaluados fueron el porcentaje de emergencia, la proporción de sexos, el número de parasitoides que surgieron por huevo y la duración del ciclo. Los experimentos se establecieron en un diseño experimental completamente al azar con cinco tratamientos (temperaturas) y 12 repeticiones. Se realizó ANOVA y se compararon las medias mediante la prueba de Tukey (P < 0.05). La temperatura base fue de 10,77 y 10,86 °C y el número de generaciones por año fue de 33,29 y 35,63 para “Ubajara” y “Guaraciaba”, respectivamente. La temperatura cambió los parámetros biológicos, y la duración del ciclo de las líneas “Ubajara” y “Guaraciaba” disminuyó a medida que aumentaba la temperatura.

Abstract This study aimed to evaluate the impact of temperature on the development of two lines of Trichogramma pretiosum (Hymenoptera: Trichogrammatidae), to determine the thermal requirements of this parasitoid wasp on Neoleucinodes elegantalis (Lepidoptera: Crambidae) eggs. The experiment was carried out with two lines (“Ubajara” and “Guaraciaba”, Ceará State) of T. pretiosum collected naturally parasitizing eggs of N. elegantalis in tomato (Solanum lycopersicum) fruits. In this experiment, 40 eggs of the host N. elegantalis and 4 females of the parasitoids were used, with exposure to parasitism for 24 hours at 25 ± 1 °C, relative humidity of 70 ± 10 %, and 12-h photophase. At the end of this period, females were removed and the tubes were transferred to incubators (RH = 70 ± 10 %; 12-h photophase), exposed to 15, 20, 25, 30, or 35 °C, until emergence of the following generation of the parasitoids. The percentage of emergence, sex ratio, the number of parasitoids that emerged per egg, and cycle duration were assessed. The experiments were set up in a completely randomized experimental design with 5 treatments (temperatures) and 12 replicates. ANOVA was conducted and the means were compared by Tukey test (P < 0.05). The base temperatures were 10.77 °C and 10.86 °C and the number of generations per year were 33.29 and 35.63 for “Ubajara” and “Guaraciaba”, respectively. The study showed that temperature changed the biological parameters, and cycle duration of the “Ubajara” and “Guaraciaba” lines decreased as temperature increased.

Resumen: Habitualmente el control de lepidópteros plaga en el cultivo de soja en Uruguay se realiza por medio de la aplicación de insecticidas químicos con riesgos para la salud y el ambiente. Como parte de un programa de control biológico inundativo por medio de Trichogramma pretiosum, un ensayo parcelario en tres sitios ubicados en el departamento de Soriano (Uruguay), en la estación de cultivo 2019-2020, comparó esa práctica convencional con diferentes dosis del parasitoide de huevos, número de cápsulas de liberación por hectárea, diferente número de liberaciones en el ciclo del cultivo y liberaciones terrestres o aéreas (con o sin cápsulas de liberación). Por el método del paño se evaluó el número de larvas por metro lineal y el porcentaje de defoliación a lo largo de 6 muestreos semanales. Si bien los mejores resultados se obtuvieron con la aplicación de insecticidas químicos, dos liberaciones de T. pretiosum por métodos terrestres separadas 20 días entre sí o 4 aplicaciones semanales por medio de un dron, ambas opciones con 200.000 parasitoides por hectárea, alcanzaron los mejores resultados por debajo de los umbrales de intervención sanitaria. Esta herramienta biológica puede diferenciar y valorizar la producción agrícola uruguaya.

Abstract: Controlling lepidopteran pests in soybean in Uruguay usually involves the application of chemical insecticides with risks to health and the environment. As part of an inundative biological control program using Trichogramma pretiosum, a plot trial at three sites located in the department of Soriano (Uruguay), in the 2019-2020 growing season, compared this conventional practice with different doses of the egg parasitoid, number of release capsules per hectare, different number of releases in the culture cycle and ground and aerial releases (with or without release capsules). Using the cloth method, the number of larvae per linear meter and the defoliation percentage were evaluated over 6 weekly samplings. Although the best results were obtained with the application of chemical insecticides, two releases of T. pretiosum by terrestrial methods, 20 days apart, or 4 weekly applications by means of a drone, reached the best results below the thresholds of sanitary intervention, both options with 200,000 parasitoids per hectare. This biological tool can differentiate and value Uruguayan agricultural production.

Resumo: O controle de lepidópteros praga no cultivo de soja no Uruguai é principalmente realizado através da aplicação de inseticidas químicos com riscos à saúde e ao meio ambiente. Como parte de um programa de controle biológico inundativo por meio de Trichogramma pretiosum, um ensaio parcelado em três locais, localizados no departamento de Soriano (Uruguai), na safra de 2019-2020, comparou essa prática convencional com diferentes doses do parasitoide de ovos, número de cápsulas de liberação por hectare, diferente número de liberações na safra e liberações terrestres ou aéreas (com ou sem cápsulas de liberação). Utilizando o método do pano-de-batida, se avaliou o número de larvas por metro linear e a porcentagem de desfolhamento em 6 amostragens semanais. Embora os melhores resultados tenham sido obtidos com a aplicação de inseticidas químicos, duas liberações de T. pretiosum por métodos terrestres separadas 20 dias um do outro ou 4 aplicações semanais por meio de um drone, ambas as opções com 200.000 parasitoides por hectare, obtiveram os melhores resultados abaixo dos limites para intervenção fitossanitária. Essa ferramenta biológica pode diferenciar e valorizar a produção agrícola uruguaia.

ABSTRACT The fall armyworm (Spodoptera frugiperda) is a major maize (Zea mays L.) pest in Brazil, whose larvae cause losses from plant emergence to harvesting stage. This pest has been controlled almost exclusively with chemical insecticides and Bt plants (transgenics); however, resistance evolution has been detected to these two control tactics. Therefore, alternative control tactics are needed for management and control of the fall armyworm. Thus, this study aimed to evaluate the resistance of maize landraces from Brazil to larvae of this herbivore in the winter and summer seasons, studying also the occurrence of the predator Doru luteipes (Dermaptera: Forficulidae). The variety Pérola had the highest resistance levels to fall armyworm in the summer season, with lower values of leaf injury, number of infested plants, and number of larvae. Conversely, this variety did not express resistance to the pest in winter. Doru luteipes was found abundantly in the summer season, showing no differences between varieties. This is the first study to evaluate the resistance of maize landraces from Brazil to fall armyworm in the winter and summer seasons. The next step is the molecular characterization of the variety Pérola, as well as evaluating its effects on the most common natural enemies of the pest in Brazil, such as the predator D. luteipes and the egg parasitoid Trichogramma pretiosum (Hymenoptera: Trichogrammatidae). These results may assist future maize breeding programs aimed at developing cultivars and hybrids resistant to the pest, and hence reducing agriculture’s dependence on chemical insecticides and transgenic plants.

Abstract The ages of parasitoid females and their hosts can have substantial effects on parasitism and parasitoid efficacy. This relationship has been investigated over the last few decades and found to vary among species. To our knowledge, it was virtually unknown for Trichogramma pretiosum wasps that parasitize Anticarsia gemmatalis eggs. Therefore, the influence of parasitoid and host age on the parasitism of T. pretiosum on eggs of A. gemmatalis was here evaluated in three independent bioassays. Neither the number of parasitized eggs nor that of emerged parasitoids differed between T. pretiosum females of different age. The number of parasitoids per egg and the sex ratio were higher for 5-day-old females. Regarding host age, the number of parasitized eggs was highest for A. gemmatalis eggs aged 24 h (9.60), followed by eggs aged 48 h (1.00), while no parasitism was observed for eggs aged 72 h. The number of parasitoids per egg and sex ratio were not influenced by host age. Preference was significantly higher for host eggs aged 24 h (79.67%), followed by eggs aged 48 h (16.99%) and 72 h (3.33%). Accordingly to these results, the key challenge for a successful T. pretiosum release to control A. gemmatalis in the field is to synchronize the presence of up to 5-day-old adults with the most susceptible phase of the host eggs (1 day).

Abstract Abstract: The dispersion capacity is fundamental to establish a biological control program with parasitoids. This information is used to determine the efficiency and the number of release points. Thus, the objective of this work was to determine the dispersion and to estimate the number of release points of Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae), in sweet corn, cucumber and cabbage in the Ceará State. The experiments were carried out in areas of maize with four leaf pairs (V4) and eight leaves pair (V8), stacked and cabbage. Unviable eggs of an alternative host were distributed in concentric circles of radius 2.5; 5.0; 9.0 and 12.0 m. Mean dispersal distance in the V4 stage maize was 4.7 m with a dispersion area of 48.6 m2, parasitism index of 18.4%, requiring 206 points/ha. In the V8 stage maize, the mean distance was 5.9 m, dispersion area of 60.3 m², mean parasitism index of 22.7% and 166 release points/ha. For the cucumber culture the mean distance was 6.0 m, dispersion area 62.2 m², mean parasitism index of 21.1% and 161 release points/ha. For cabbage the mean distance was 5.6 m, dispersion area of 56.8 m², mean parasitism index of 22.1% and 176 release points/ha.

RESUMO O estudo objetivou avaliar uma linhagem de Trichogramma pretiosum nativa da região Central do Rio Grande do Sul (Brasil) sob diferentes temperaturas em laboratório, e no parasitismo de Helicoverpa zea após liberações em área de milho. Fêmeas de T. pretiosum foram mantidas a 18, 25 e 30 °C e avaliadas quanto ao potencial de parasitismo. No campo, foram instaladas nove parcelas (400 m2) de milho híbrido em blocos ao acaso, com os seguintes tratamentos: 1) liberação de parasitoides fracionada em três vezes, em intervalos de três dias; 2) liberação em apenas uma ocasião; 3) sem liberação. A cada quatro dias foram coletadas espigas e registrados os danos e o número de lagartas e ovos de H. zea dos estilos-estigmas. A avaliação iniciou durante o pendoamento e estendeu-se até a fase de secagem dos estilos-estigma. Duas linhas em cada parcela foram reservadas para avaliação do número e da massa de espigas e grãos. Em laboratório, o maior percentual de parasitismo foi aos 25 °C (35,54%) e a menor longevidade aos 30 °C (6,8 dias). No campo, foram coletados 1.063 ovos de H. zea, dos quais 69,52% estavam parasitados. O percentual médio de parasitismo foi maior com liberação escalonada de T. pretiosum (82,77%), comparativamente ao controle (51,87%), porém, não houve diferença na produção de grãos. Tendo em vista a capacidade de parasitismo da linhagem avaliada, sugere-se que ela possui potencial para ser utilizada em programas de controle biológico da lagarta da espiga no cultivo de milho no Rio Grande do Sul.

ABSTRACT This study aimed to evaluate a strain of Trichogramma pretiosum native to the central region of the state Rio Grande do Sul, Brazil, under different temperatures in laboratory and the parasitism of Helicoverpa zea after releases in corn field. Trichogramma pretiosum females were kept at 18, 25 and 30 °C and had their parasitism potential evaluated. Nine plots (400 m2) of maize were installed in randomized blocks under the treatments: 1) staggered release of parasitoids in three different occasions, at three-day intervals; 2) a single release of parasitoids; 3) no release of parasitoids. Ears were collected every four days and the number of caterpillars and eggs of H. zea in the maize silk and the number of damaged ears were estimated. Evaluation started after the tassels growth and ended with the drying of the styles-stigmas. To estimate the grain mass and the ear number and mass, two lines in each plot were delimited and reserved at the end of the cultivation cycle. In laboratory, the highest parasitism rate occurred at 25 °C (35.54%) and the lowest longevity at 30 °C (6.8 days). A total of 1,063 H. zea eggs were collected in the field, 69.52% were parasitized. The mean parasitism rate was higher in T1 (staggered release, 82.77%) than in control (51.87%), but there was no difference in grain yield. Based on the parasitism capacity of the studied strain, it can be potentially used in programs of biological control of H. zea in corn crops of Rio Grande do Sul.

RESUMO Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae) é parasitoide de ovos de lepidópteros praga no milho, Zea mays L. (Poaceae), no Brasil. Produtos químicos usados na agricultura podem ser tóxicos para este agente de controle biológico. O objetivo do presente estudo foi avaliar a longevidade, parasitismo e emergência de T. pretiosum em ovos da traça da farinha, Anagasta kuehniella Zeller, 1879 (Lepidoptera: Pyralidae) tratados com soluções herbicidas com os ingredientes ativos (grupo químico) atrazina (triazinas), dicloreto de paraquate (bipiridílio) e nicosulfuron (sulfonilureia). Água destilada pura foi usada como controle negativo e a solução de um produto com λ-cialotrina + tiametoxam (piretróide + neonicotinóide, respectivamente) foi usada como controle positivo. O delineamento experimental foi inteiramente casualizado, com cinco tratamentos e 10 repetições. Ovos de A. kuehniella foram armazenados por dois períodos após tratamento, 24 e 48 horas. Esses ovos foram submetidos ao parasitismo por dois períodos de submissão, 24 e 48 horas. Os resultados foram analisados estatisticamente e classificados de acordo com a International Organization for Biological Control (IOBC). Atrazina e nicosulfuron reduziram a longevidade das fêmeas de T. pretiosum. Nicosulfuron e a combinação λ-cialotrina + tiametoxam reduziram o parasitismo e a emergência deste inimigo natural. O herbicida à base de dicloreto de paraquate foi o menos tóxico e, por isto, representa uma opção em potencial para o controle de plantas daninhas com baixa toxicidade ao parasitóide T. pretiosum.

ABSTRACT Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae) is an egg parasitoid of lepidopteran pests in corn, Zea mays L. (Poaceae), in Brazil. Chemical products used in agriculture can be toxic to this biocontrol agent. The objective of the present study was to evaluate the longevity, parasitism and emergence of T. pretiosum parasitizing Mediterranean flour moth, Anagasta kuehniella Zeller, 1879 (Lepidoptera: Pyralidae), eggs treated with herbicide solutions with the active ingredients (chemical group) atrazine (triazines), paraquat dichloride (bipyridylium) and nicosulfuron (sulfonylurea). Pure distilled water was used as a negative control, and a solution of a product with λ-cyhalothrin + thiamethoxam (pyrethroid + neonicotinoid, respectively) was used as the positive control. The experimental design was completely randomized, with five treatments and 10 replicates. Anagasta kuehniella eggs were stored for two periods after treatment, 24 and 48 hours. These eggs were subjected to parasitism for two subjecting periods, 24 and 48 hours. The results were analysed statistically and classified according to the International Organization for Biological Control (IOBC). Atrazine and nicosulfuron reduced the longevity of T. pretiosum females. Nicosulfuron and the combination λ-cyhalothrin + thiamethoxam reduced the parasitism and emergence of this natural enemy. The paraquat dichloride-based herbicide was the least toxic and therefore represents a potential option for controlling weeds with low toxicity to the T. pretiosum parasitoid.

RESUMO: Informações sobre herbicidas seletivos, incluindo o glyphosate, que não afetam organismos não alvo, como inimigos naturais, são importantes nos programas de manejo integrado de pragas na cultura do milho. O glyphosate, na dose de 13,94 L ha-1, foi avaliado em fêmeas de 10 espécies de Trichogrammatidae (Hymenoptera). Uma fêmea de cada espécie de Trichogrammatidae foi posicionada individualmente por tubo de ensaio em cartelas contendo aproximadamente 45 ovos de Anagasta kuehniella Zeller, 1879 (Lepidoptera: Pyralidae). Durante 48 horas o parasitismo foi permitido e, posteriormente, as cartelas foram pulverizadas com o herbicida ou com água destilada, para o tratamento controle. O herbicida mostrou efeitos variáveis para as espécies de parasitoides. A emergência de fêmeas de T. acacioi foi menor, e a daquelas de T. atopovilia, T. demoraesi e T. pretiosum foi maior com glyphosate. A razão sexual de T. galloi foi menor, e a de T. bruni , T. brasiliensis , T. demoraesi e T. soaresi maior com glyphosate. Esse herbicida foi pouco tóxico para todas as espécies de Trichogrammatidae com base na classificação adotada internacionalmente.

ABSTRACT: Information on selective herbicide, including glyphosate that does not affect non-target organisms such as natural enemies, are important in integrated pest management programs in maize. The dose 13.94 L ha-1 of glyphosate was evaluated in females on 10 Trichogrammatidae species. A female of each Trichogrammatidae species was individually positioned per test tube with a card containing approximately 45 Anagasta kuehniella Zeller, 1879 (Lepidoptera: Pyralidae) eggs. For 48 h parasitism was allowed, and later the cartons were sprayed with the herbicide or with distilled water, for the control treatment. The glyphosate showed variable effects for parasitoids. The emergence of T. acacioi females was lower but that of T. atopovilia, T. demoraesi, and T. pretiosum higher with the glyphosate. The sex ratio of T. galloi was lower and that of T. bruni, T. brasiliensis, T. demoraesi, and T. soaresi higher with glyphosate. This glyphosate was innocuous to all Trichogrammatidae species females based on the classification adopted internationally.

ABSTRACT This study investigated the interaction between two pest biological control agents, the parasitoid wasp Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) and the entomopathogen Bacillus thuringiensis (Bacillales: Bacillacea) (Bt). The aim of this study was to evaluate if the presence of Bt (formulated products Agree®, Dipel® and HD1 and HD11 strains) interferes in the oviposition preference of T. pretiosum to eggs of Helicoverpa zea (Lepidoptera: Noctuidae). Using an olfactometry test, the eggs of H. zea were bathed with the commercial formulations, with the Bt suspensions or distilled water, and offered to the parasitoid wasps in order to evaluate parasitism. The results showed that H. zea eggs sprayed with commercial formulations and Bt strains did not interfere in the choice made by the parasitoid. The parasitoid wasp is not able to distinguish between eggs with or without B. thuringiensis treatment, independently of strains suspension or commercial formulations. Therefore, these two control agents may be used together without negative interaction.